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Seq	Timestamp	Type	Name	Duration
0/0	2026/09/23 23:22	flow	patch-triage	3m Args: null Results: { "EnableConfigs": [ "MEM_ALLOC_PROFILING", "MEM_ALLOC_PROFILING_ENABLED_BY_DEFAULT", "PROC_FS", "TRACING", "MODULES" ], "FocusSymbols": [ "allocinfo_ioctl", "allocinfo_ioctl_toggle_trace", "alloc_tag_trace_toggle", "__alloc_tag_trace_hit", "alloc_tag_trace_mem_alloc", "alloc_tag_trace_mem_free", "unload_module" ], "KMSANReasoning": "The patch introduces tracepoints and an ioctl interface (`ALLOCINFO_IOC_TOGGLE_TRACE`) for memory allocation profiling (`alloc_tag`), as well as adding a `trace_on` field to `struct allocinfo_counter` in the UAPI header.\n\n1. Kernel-to-user info-leak analysis:\nAlthough `struct allocinfo_counter` has its padding adjusted (`pad[7]` reduced to `trace_on` + `pad[6]`), the kernel structures containing it (`allocinfo_get_at` and `allocinfo_tag_data`) are fully zero-initialized with `= {0}` or `memset` in `allocinfo_ioctl_get_at()` and `allocinfo_ioctl_get_next()` prior to copying to user space. Furthermore, the new field `data-\u003ecounter.trace_on` is explicitly assigned in `allocinfo_to_params()`. The new ioctl `ALLOCINFO_IOC_TOGGLE_TRACE` only reads user input via `copy_from_user()` and does not copy any data back to user space.\n\n2. Uninitialized memory access analysis:\nCodetags are statically initialized via `CODETAG_INIT` (`.flags = ATOMIC_INIT(0)`) or allocated/managed during module load. All flags, static keys, and atomic variables are properly initialized before being read. The new tracepoints (`alloc_tag_hit`, `alloc_tag_mem_alloced`, `alloc_tag_mem_freed`) only record initialized pointer references, sizes, and codetag metadata.\n\n3. KASAN / LOCKDEP applicability:\nAny potential issues introduced by this patch (such as concurrency between module unloading and ioctl trace toggles, static branch updates, or pointer validity) fall strictly within the scope of KASAN, LOCKDEP, and standard kernel bug detectors.\n\nTherefore, there is no risk of uninitialized memory usage or information disclosure, and a dedicated KMSAN fuzzing session is not warranted.", "NeedsKMSAN": false, "Reasoning": "The patch adds tracepoints and dynamic tracing support to the memory allocation profiling subsystem (alloc_tag). It exposes a new ioctl command ALLOCINFO_IOC_TOGGLE_TRACE on /proc/allocinfo to selectively enable/disable tracing per codetag, introduces mutex locking and static branch toggling, and hooks trace events into core allocation and deallocation paths as well as module unload callbacks. These changes touch reachable core memory management and procfs code that warrants fuzzing for potential race conditions, refcounting issues, or crashes.", "WorthFuzzing": true }
1/1	2026/09/23 23:22	action	read-patch-diff	0m Args: null Results: { "PatchDiff": "commit 1886759b63636a8dc8de5d530fbcb5c06d554e68\nAuthor: syz-cluster \u003ctriage@syzkaller.com\u003e\nDate: Wed Sep 23 23:22:34 2026 +0000\n\n syz-cluster: applied patch under review\n\ndiff --git a/MAINTAINERS b/MAINTAINERS\nindex 24420a8c06d02..29e1f7915cb98 100644\n--- a/MAINTAINERS\n+++ b/MAINTAINERS\n@@ -17096,6 +17096,7 @@ S:\tMaintained\n F:\tDocumentation/mm/allocation-profiling.rst\n F:\tinclude/linux/alloc_tag.h\n F:\tinclude/linux/pgalloc_tag.h\n+F:\tinclude/trace/events/alloc_tag.h\n F:\tinclude/uapi/linux/alloc_tag.h\n F:\tmm/alloc_tag.c\n F:\ttools/testing/selftests/alloc_tag/\ndiff --git a/include/linux/alloc_tag.h b/include/linux/alloc_tag.h\nindex 7f2d80a597924..dc86f8997476c 100644\n--- a/include/linux/alloc_tag.h\n+++ b/include/linux/alloc_tag.h\n@@ -128,12 +128,60 @@ DECLARE_PER_CPU(struct alloc_tag_counters, _shared_alloc_tag);\n DECLARE_STATIC_KEY_MAYBE(CONFIG_MEM_ALLOC_PROFILING_ENABLED_BY_DEFAULT,\n \t\t\tmem_alloc_profiling_key);\n \n+DECLARE_STATIC_KEY_FALSE(alloc_tag_trace_key);\n+\n static inline bool mem_alloc_profiling_enabled(void)\n {\n \treturn static_branch_maybe(CONFIG_MEM_ALLOC_PROFILING_ENABLED_BY_DEFAULT,\n \t\t\t\t \u0026mem_alloc_profiling_key);\n }\n \n+static inline void alloc_tag_set_inaccurate(struct alloc_tag tag)\n+{\n+\tatomic_or(CODETAG_FLAG_INACCURATE, \u0026tag-\u003ect.flags);\n+}\n+\n+static inline bool alloc_tag_is_inaccurate(struct alloc_tag tag)\n+{\n+\treturn !!(atomic_read(\u0026tag-\u003ect.flags) \u0026 CODETAG_FLAG_INACCURATE);\n+}\n+\n+static inline void alloc_tag_set_traced(struct alloc_tag tag)\n+{\n+\tatomic_or(CODETAG_FLAG_TRACE_ON, \u0026tag-\u003ect.flags);\n+}\n+\n+static inline void alloc_tag_clear_traced(struct alloc_tag tag)\n+{\n+\tatomic_andnot(CODETAG_FLAG_TRACE_ON, \u0026tag-\u003ect.flags);\n+}\n+\n+static inline bool alloc_tag_is_traced(const struct alloc_tag tag)\n+{\n+\treturn !!(atomic_read(\u0026tag-\u003ect.flags) \u0026 CODETAG_FLAG_TRACE_ON);\n+}\n+\n+static inline bool alloc_tag_trace_enabled(const struct alloc_tag tag)\n+{\n+\tif (static_branch_unlikely(\u0026alloc_tag_trace_key))\n+\t\treturn tag \u0026\u0026 alloc_tag_is_traced(tag);\n+\treturn false;\n+}\n+\n+void alloc_tag_trace_mem_alloc(union codetag_ref ref, struct alloc_tag tag,\n+\t\t\t size_t bytes);\n+\n+void alloc_tag_trace_mem_free(union codetag_ref ref, struct alloc_tag tag,\n+\t\t\t size_t bytes);\n+\n+void __alloc_tag_trace_hit(struct alloc_tag tag);\n+\n+static inline void alloc_tag_trace_hit(struct alloc_tag tag)\n+{\n+\tif (alloc_tag_trace_enabled(tag))\n+\t\t__alloc_tag_trace_hit(tag);\n+}\n+\n bool mem_alloc_profiling_permanently_disabled(void);\n \n static inline struct alloc_tag_counters alloc_tag_read(struct alloc_tag tag)\n@@ -200,8 +248,13 @@ static inline bool alloc_tag_ref_set(union codetag_ref ref, struct alloc_tag t\n \n static inline void alloc_tag_add(union codetag_ref ref, struct alloc_tag tag, size_t bytes)\n {\n-\tif (likely(alloc_tag_ref_set(ref, tag)))\n+\tif (likely(alloc_tag_ref_set(ref, tag))) {\n \t\tthis_cpu_add(tag-\u003ecounters-\u003ebytes, bytes);\n+\n+\t\tif (alloc_tag_trace_enabled(tag))\n+\t\t\t/ Trace successful allocs with their unique ref /\n+\t\t\talloc_tag_trace_mem_alloc(ref, tag, bytes);\n+\t}\n }\n \n static inline void alloc_tag_sub(union codetag_ref ref, size_t bytes)\n@@ -222,17 +275,11 @@ static inline void alloc_tag_sub(union codetag_ref ref, size_t bytes)\n \tthis_cpu_sub(tag-\u003ecounters-\u003ebytes, bytes);\n \tthis_cpu_dec(tag-\u003ecounters-\u003ecalls);\n \n-\tref-\u003ect = NULL;\n-}\n-\n-static inline void alloc_tag_set_inaccurate(struct alloc_tag tag)\n-{\n-\ttag-\u003ect.flags \|= CODETAG_FLAG_INACCURATE;\n-}\n+\tif (alloc_tag_trace_enabled(tag))\n+\t\t/* Trace frees with their unique ref /\n+\t\talloc_tag_trace_mem_free(ref, tag, bytes);\n \n-static inline bool alloc_tag_is_inaccurate(struct alloc_tag tag)\n-{\n-\treturn !!(tag-\u003ect.flags \u0026 CODETAG_FLAG_INACCURATE);\n+\tref-\u003ect = NULL;\n }\n \n #define alloc_tag_record(p)\t((p) = current-\u003ealloc_tag)\n@@ -247,21 +294,24 @@ static inline void alloc_tag_add(union codetag_ref ref, struct alloc_tag tag,\n static inline void alloc_tag_sub(union codetag_ref ref, size_t bytes) {}\n static inline void alloc_tag_set_inaccurate(struct alloc_tag tag) {}\n static inline bool alloc_tag_is_inaccurate(struct alloc_tag tag) { return false; }\n+#define alloc_tag_trace_hit(_tag)\t/ NOOP /\n #define alloc_tag_record(p)\tdo {} while (0)\n \n #endif / CONFIG_MEM_ALLOC_PROFILING /\n \n-#define alloc_hooks_tag(_tag, _do_alloc)\t\t\t\t\\\n-({\t\t\t\t\t\t\t\t\t\\\n-\ttypeof(_do_alloc) _res;\t\t\t\t\t\t\\\n-\tif (mem_alloc_profiling_enabled()) {\t\t\t\t\\\n-\t\tstruct alloc_tag __maybe_unused _old;\t\t\t\\\n-\t\t_old = alloc_tag_save(_tag);\t\t\t\t\\\n-\t\t_res = _do_alloc;\t\t\t\t\t\\\n-\t\talloc_tag_restore(_tag, _old);\t\t\t\t\\\n-\t} else\t\t\t\t\t\t\t\t\\\n-\t\t_res = _do_alloc;\t\t\t\t\t\\\n-\t_res;\t\t\t\t\t\t\t\t\\\n+#define alloc_hooks_tag(_tag, _do_alloc)\t\t\t\t\t\\\n+({\t\t\t\t\t\t\t\t\t\t\\\n+\ttypeof(_do_alloc) _res;\t\t\t\t\t\t\t\\\n+\tif (mem_alloc_profiling_enabled()) {\t\t\t\t\t\\\n+\t\tstruct alloc_tag * __maybe_unused _old;\t\t\t\t\\\n+\t\t/* Fired here to cleanly capture the caller's stack trace /\t\\\n+\t\talloc_tag_trace_hit(_tag);\t\t\t\t\t\\\n+\t\t_old = alloc_tag_save(_tag);\t\t\t\t\t\\\n+\t\t_res = _do_alloc;\t\t\t\t\t\t\\\n+\t\talloc_tag_restore(_tag, _old);\t\t\t\t\t\\\n+\t} else\t\t\t\t\t\t\t\t\t\\\n+\t\t_res = _do_alloc;\t\t\t\t\t\t\\\n+\t_res;\t\t\t\t\t\t\t\t\t\\\n })\n \n #define alloc_hooks(_do_alloc)\t\t\t\t\t\t\\\ndiff --git a/include/linux/codetag.h b/include/linux/codetag.h\nindex a25a085c2df19..f728295d50c05 100644\n--- a/include/linux/codetag.h\n+++ b/include/linux/codetag.h\n@@ -18,6 +18,7 @@ struct module;\n \n / codetag flags /\n #define CODETAG_FLAG_INACCURATE\t(1 \u003c\u003c 0)\n+#define CODETAG_FLAG_TRACE_ON\t(1 \u003c\u003c 1)\n \n /\n * An instance of this structure is created in a special ELF section at every\n@@ -25,7 +26,7 @@ struct module;\n * an array of these.\n /\n struct codetag {\n-\tunsigned int flags;\n+\tatomic_t flags;\n \tunsigned int lineno;\n \tconst char modname;\n \tconst char function;\n@@ -71,7 +72,7 @@ struct codetag_iterator {\n \t.function\t= __func__,\t\t\t\\\n \t.filename\t= __FILE__,\t\t\t\\\n \t.lineno\t\t= __LINE__,\t\t\t\\\n-\t.flags\t\t= 0,\t\t\t\t\\\n+\t.flags\t\t= ATOMIC_INIT(0),\t\t\\\n }\n \n void codetag_lock_module_list(struct codetag_type cttype);\ndiff --git a/include/trace/events/alloc_tag.h b/include/trace/events/alloc_tag.h\nnew file mode 100644\nindex 0000000000000..af2182501864c\n--- /dev/null\n+++ b/include/trace/events/alloc_tag.h\n@@ -0,0 +1,122 @@\n+/* SPDX-License-Identifier: GPL-2.0 /\n+#undef TRACE_SYSTEM\n+#define TRACE_SYSTEM alloc_tag\n+\n+#if !defined(_TRACE_ALLOC_TAG_H) \|\| defined(TRACE_HEADER_MULTI_READ)\n+#define _TRACE_ALLOC_TAG_H\n+\n+#include \u003clinux/tracepoint.h\u003e\n+\n+/\n+ * alloc_tag_hit is generated at the exact allocation call site and can be\n+ * used to capture a clean stack trace.\n+ \n+ To link this stack trace to the actual allocated memory chunk, tools must\n+ * correlate this event with the resulting alloc_tag_mem_alloced event. Since\n+ * multiple threads can hit the same tag simultaneously, tools must match BOTH\n+ * the `tag` field and the implicitly recorded PID provided by the core\n+ * tracing subsystem.\n+ /\n+TRACE_EVENT(alloc_tag_hit,\n+\n+\tTP_PROTO(struct alloc_tag tag),\n+\n+\tTP_ARGS(tag),\n+\n+\tTP_STRUCT__entry(\n+\t\t__field(struct alloc_tag , tag)\n+\t\t__string(modname, tag-\u003ect.modname ? tag-\u003ect.modname : \"NONE\")\n+\t\t__string(filename, tag-\u003ect.filename)\n+\t\t__string(function, tag-\u003ect.function)\n+\t\t__field(unsigned int, lineno)\n+\t),\n+\n+\tTP_fast_assign(\n+\t\t__entry-\u003etag = tag;\n+\t\t__assign_str(modname);\n+\t\t__assign_str(filename);\n+\t\t__assign_str(function);\n+\t\t__entry-\u003elineno = tag-\u003ect.lineno;\n+\t),\n+\n+\tTP_printk(\"tag %p, module: %s, filename: %s, function %s, lineno %u\",\n+\t\t__entry-\u003etag,\n+\t\t__get_str(modname),\n+\t\t__get_str(filename),\n+\t\t__get_str(function),\n+\t\t__entry-\u003elineno\n+\t)\n+);\n+\n+/\n+ * alloc_tag_mem_alloced is generated after memory is successfully allocated.\n+ * It captures the exact byte size.\n+ \n+ The `ref` pointer identifies the memory chunk for tracking its lifecycle\n+ * (e.g., matching it with alloc_tag_mem_freed).\n+ \n+ Because the kernel isolates active allocations within the task struct\n+ * (current-\u003ealloc_tag), this even will always share the same implicit PID as\n+ * its corresponding alloc_tag_hit event. Tools should use the combination\n+ * PID + `tag` to correlate them.\n+ /\n+TRACE_EVENT(alloc_tag_mem_alloced,\n+\n+\tTP_PROTO(union codetag_ref ref, struct alloc_tag tag, size_t bytes),\n+\n+\tTP_ARGS(ref, tag, bytes),\n+\n+\tTP_STRUCT__entry(\n+\t\t__field(union codetag_ref , ref)\n+\t\t__field(struct alloc_tag , tag)\n+\t\t__field(size_t, bytes)\n+\t),\n+\n+\tTP_fast_assign(\n+\t\t__entry-\u003eref = ref;\n+\t\t__entry-\u003etag = tag;\n+\t\t__entry-\u003ebytes = bytes;\n+\t),\n+\n+\tTP_printk(\"reference %p, tag %p, bytes %zu\",\n+\t\t__entry-\u003eref,\n+\t\t__entry-\u003etag,\n+\t\t__entry-\u003ebytes\n+\t)\n+);\n+\n+/\n+ * alloc_tag_mem_freed event is generated immediately before memory is\n+ * freed. The `ref` pointer matches the one emitted during allocation,\n+ * allowing tools to match it to it's corresponding allocation and\n+ * call stack.\n+ /\n+TRACE_EVENT(alloc_tag_mem_freed,\n+\n+\tTP_PROTO(union codetag_ref ref, struct alloc_tag tag, size_t bytes),\n+\n+\tTP_ARGS(ref, tag, bytes),\n+\n+\tTP_STRUCT__entry(\n+\t\t__field(union codetag_ref , ref)\n+\t\t__field(struct alloc_tag , tag)\n+\t\t__field(size_t, bytes)\n+\t),\n+\n+\tTP_fast_assign(\n+\t\t__entry-\u003eref = ref;\n+\t\t__entry-\u003etag = tag;\n+\t\t__entry-\u003ebytes = bytes;\n+\t),\n+\n+\tTP_printk(\"reference %p, tag %p, bytes %zu\",\n+\t\t__entry-\u003eref,\n+\t\t__entry-\u003etag,\n+\t\t__entry-\u003ebytes\n+\t)\n+);\n+\n+#endif / _TRACE_ALLOC_TAG_H /\n+\n+/ This part must be outside protection /\n+#include \u003ctrace/define_trace.h\u003e\ndiff --git a/include/uapi/linux/alloc_tag.h b/include/uapi/linux/alloc_tag.h\nindex 7d4618bea0434..e65c32afceee2 100644\n--- a/include/uapi/linux/alloc_tag.h\n+++ b/include/uapi/linux/alloc_tag.h\n@@ -38,7 +38,8 @@ struct allocinfo_counter {\n \t__u64 bytes;\n \t__u64 calls;\n \t__u8 accurate;\n-\t__u8 pad[7];\n+\t__u8 trace_on;\n+\t__u8 pad[6];\n } __attribute__((aligned(8)));\n \n struct allocinfo_tag_data {\n@@ -54,7 +55,8 @@ enum {\n \tALLOCINFO_FILTER_INACCURATE,\n \tALLOCINFO_FILTER_MIN_SIZE,\n \tALLOCINFO_FILTER_MAX_SIZE,\n-\t__ALLOCINFO_FILTER_LAST = ALLOCINFO_FILTER_MAX_SIZE\n+\tALLOCINFO_FILTER_TRACE_ON,\n+\t__ALLOCINFO_FILTER_LAST = ALLOCINFO_FILTER_TRACE_ON\n };\n \n #define ALLOCINFO_FILTER_MASK_MODNAME\t\t(1 \u003c\u003c ALLOCINFO_FILTER_MODNAME)\n@@ -64,6 +66,7 @@ enum {\n #define ALLOCINFO_FILTER_MASK_INACCURATE\t(1 \u003c\u003c ALLOCINFO_FILTER_INACCURATE)\n #define ALLOCINFO_FILTER_MASK_MIN_SIZE\t\t(1 \u003c\u003c ALLOCINFO_FILTER_MIN_SIZE)\n #define ALLOCINFO_FILTER_MASK_MAX_SIZE\t\t(1 \u003c\u003c ALLOCINFO_FILTER_MAX_SIZE)\n+#define ALLOCINFO_FILTER_MASK_TRACE_ON\t\t(1 \u003c\u003c ALLOCINFO_FILTER_TRACE_ON)\n \n #define ALLOCINFO_FILTER_MASKS \\\n \t((1 \u003c\u003c (__ALLOCINFO_FILTER_LAST + 1)) - 1)\n@@ -75,6 +78,7 @@ struct allocinfo_filter {\n \t__u64 max_size;\n \t/ filter criteria only; see allocinfo_counter.accurate for actual accuracy /\n \t__u64 inaccurate;\n+\t__u64 tracing;\n };\n \n struct allocinfo_get_at {\n@@ -85,9 +89,16 @@ struct allocinfo_get_at {\n \tstruct allocinfo_tag_data data;\n };\n \n+struct allocinfo_toggle_traces {\n+\t/ inputs /\n+\tstruct allocinfo_tag fields;\n+\t__u64 enable;\n+};\n+\n #define _ALLOCINFO_IOC_CONTENT_ID\t0\n #define _ALLOCINFO_IOC_GET_AT\t\t1\n #define _ALLOCINFO_IOC_GET_NEXT\t\t2\n+#define _ALLOCINFO_IOC_TOGGLE_TRACE\t3\n \n #define ALLOCINFO_IOC_BASE\t\t0xA6\n #define ALLOCINFO_IOC_CONTENT_ID\t_IOR(ALLOCINFO_IOC_BASE, _ALLOCINFO_IOC_CONTENT_ID,\t\\\n@@ -96,5 +107,7 @@ struct allocinfo_get_at {\n \t\t\t\t\t struct allocinfo_get_at)\n #define ALLOCINFO_IOC_GET_NEXT\t\t_IOR(ALLOCINFO_IOC_BASE, _ALLOCINFO_IOC_GET_NEXT,\t\\\n \t\t\t\t\t struct allocinfo_tag_data)\n+#define ALLOCINFO_IOC_TOGGLE_TRACE\t_IOW(ALLOCINFO_IOC_BASE, _ALLOCINFO_IOC_TOGGLE_TRACE,\t\\\n+\t\t\t\t\t struct allocinfo_toggle_traces)\n \n #endif / _UAPI_ALLOC_TAG_H /\ndiff --git a/mm/alloc_tag.c b/mm/alloc_tag.c\nindex f30ef8dd24c70..50632b627d92b 100644\n--- a/mm/alloc_tag.c\n+++ b/mm/alloc_tag.c\n@@ -19,6 +19,9 @@\n #include \u003clinux/kmemleak.h\u003e\n #include \u003cuapi/linux/alloc_tag.h\u003e\n \n+#define CREATE_TRACE_POINTS\n+#include \u003ctrace/events/alloc_tag.h\u003e\n+\n #include \"internal.h\"\n #include \"page_alloc.h\"\n \n@@ -55,6 +58,18 @@ EXPORT_SYMBOL(mem_alloc_profiling_key);\n \n DEFINE_STATIC_KEY_FALSE(mem_profiling_compressed);\n \n+DEFINE_STATIC_KEY_FALSE(alloc_tag_trace_key);\n+EXPORT_SYMBOL(alloc_tag_trace_key);\n+\n+static atomic_t alloc_tag_trace_cnt = ATOMIC_INIT(0);\n+\n+/\n+ * As `codetag_lock_module_list` is a read lock, we need an additional mutex\n+ * to protect against the race conditions involved in the alloc tag trace\n+ * toggle path.\n+ /\n+static DEFINE_MUTEX(alloc_tag_trace_mutex);\n+\n struct alloc_tag_kernel_section kernel_tags = { NULL, 0 };\n unsigned long alloc_tag_ref_mask;\n int alloc_tag_ref_offs;\n@@ -236,6 +251,7 @@ static void allocinfo_to_params(struct codetag ct,\n \tdata-\u003ecounter.bytes = counters-\u003ebytes;\n \tdata-\u003ecounter.calls = counters-\u003ecalls;\n \tdata-\u003ecounter.accurate = !alloc_tag_is_inaccurate(ct_to_alloc_tag(ct));\n+\tdata-\u003ecounter.trace_on = alloc_tag_is_traced(ct_to_alloc_tag(ct));\n }\n \n /\n@@ -291,7 +307,7 @@ static bool matches_filter(struct codetag ct, struct allocinfo_filter filter,\n \t\treturn false;\n \n \tif (filter-\u003emask \u0026 ALLOCINFO_FILTER_MASK_INACCURATE) {\n-\t\tinaccurate = !!(ct-\u003eflags \u0026 CODETAG_FLAG_INACCURATE);\n+\t\tinaccurate = alloc_tag_is_inaccurate(ct_to_alloc_tag(ct));\n \t\tif (inaccurate != !!(filter-\u003einaccurate))\n \t\t\treturn false;\n \t}\n@@ -309,6 +325,13 @@ static bool matches_filter(struct codetag ct, struct allocinfo_filter filter,\n \t\t\treturn false;\n \t}\n \n+\tif (filter-\u003emask \u0026 ALLOCINFO_FILTER_MASK_TRACE_ON) {\n+\t\tbool tracing = alloc_tag_is_traced(ct_to_alloc_tag(ct));\n+\n+\t\tif (tracing != !!(filter-\u003etracing))\n+\t\t\treturn false;\n+\t}\n+\n \treturn true;\n }\n \n@@ -438,6 +461,81 @@ static int allocinfo_ioctl_get_next(struct seq_file m, void __user arg)\n \treturn ret;\n }\n \n+static bool alloc_tag_trace_toggle(struct alloc_tag tag, bool enable)\n+{\n+\tif (enable) {\n+\t\tif (alloc_tag_is_traced(tag))\n+\t\t\treturn false;\n+\n+\t\talloc_tag_set_traced(tag);\n+\t\tif (atomic_fetch_inc(\u0026alloc_tag_trace_cnt) == 0)\n+\t\t\tstatic_branch_enable(\u0026alloc_tag_trace_key);\n+\t} else {\n+\t\tif (!alloc_tag_is_traced(tag))\n+\t\t\treturn false;\n+\n+\t\talloc_tag_clear_traced(tag);\n+\t\tif (atomic_dec_and_test(\u0026alloc_tag_trace_cnt))\n+\t\t\tstatic_branch_disable(\u0026alloc_tag_trace_key);\n+\t}\n+\n+\treturn true;\n+}\n+\n+/\n+ Toggles context capture for a specified allocation.\n+ /\n+static int allocinfo_ioctl_toggle_trace(struct seq_file m, void __user arg)\n+{\n+\tstruct allocinfo_toggle_traces params;\n+\tstruct codetag_iterator iter;\n+\tstruct codetag ct;\n+\tint matches = 0, successes = 0, ret;\n+\n+\tif (!capable(CAP_SYS_ADMIN))\n+\t\treturn -EPERM;\n+\n+\tif (copy_from_user(\u0026params, arg, sizeof(params)))\n+\t\treturn -EFAULT;\n+\n+\tcodetag_lock_module_list(alloc_tag_cttype);\n+\n+\tstruct allocinfo_filter filter = {\n+\t\t.mask = ALLOCINFO_FILTER_MASK_MODNAME \|\n+\t\t ALLOCINFO_FILTER_MASK_FUNCTION \|\n+\t\t ALLOCINFO_FILTER_MASK_FILENAME \|\n+\t\t ALLOCINFO_FILTER_MASK_LINENO,\n+\t\t.fields = params.fields,\n+\t};\n+\n+\titer = codetag_get_ct_iter(alloc_tag_cttype);\n+\n+\t/* Toggle tracing on all codetags that match /\n+\twhile ((ct = codetag_next_ct(\u0026iter))) {\n+\t\tif (matches_filter(ct, \u0026filter, NULL, NULL)) {\n+\t\t\tmatches++;\n+\n+\t\t\tmutex_lock(\u0026alloc_tag_trace_mutex);\n+\t\t\tif (alloc_tag_trace_toggle(ct_to_alloc_tag(ct), !!params.enable))\n+\t\t\t\tsuccesses++;\n+\t\t\tmutex_unlock(\u0026alloc_tag_trace_mutex);\n+\t\t}\n+\t}\n+\n+\tif (matches == 0)\n+\t\t/ Nothing matched the filter /\n+\t\tret = -ENOENT;\n+\telse if (successes == 0)\n+\t\t/ Items matched, but were already in the requested state /\n+\t\tret = -EINVAL;\n+\telse\n+\t\tret = 0;\n+\n+\tcodetag_unlock_module_list(alloc_tag_cttype);\n+\n+\treturn ret;\n+}\n+\n /\n * Entry point ioctl function for /proc/allocinfo routing requests to fetch the\n * layout content ID, seek to a specific tag, or read sequential tags.\n@@ -458,6 +556,9 @@ static long allocinfo_ioctl(struct file file, unsigned int cmd,\n \tcase ALLOCINFO_IOC_GET_NEXT:\n \t\tret = allocinfo_ioctl_get_next(file-\u003eprivate_data, arg);\n \t\tbreak;\n+\tcase ALLOCINFO_IOC_TOGGLE_TRACE:\n+\t\tret = allocinfo_ioctl_toggle_trace(file-\u003eprivate_data, arg);\n+\t\tbreak;\n \tdefault:\n \t\tret = -ENOIOCTLCMD;\n \t\tbreak;\n@@ -485,6 +586,26 @@ static const struct proc_ops allocinfo_proc_ops = {\n #endif\n };\n \n+void __alloc_tag_trace_hit(struct alloc_tag tag)\n+{\n+\ttrace_alloc_tag_hit(tag);\n+}\n+EXPORT_SYMBOL(__alloc_tag_trace_hit);\n+\n+void alloc_tag_trace_mem_alloc(union codetag_ref ref, struct alloc_tag tag,\n+\t\t\t size_t bytes)\n+{\n+\ttrace_alloc_tag_mem_alloced(ref, tag, bytes);\n+}\n+EXPORT_SYMBOL(alloc_tag_trace_mem_alloc);\n+\n+void alloc_tag_trace_mem_free(union codetag_ref ref, struct alloc_tag tag,\n+\t\t\t size_t bytes)\n+{\n+\ttrace_alloc_tag_mem_freed(ref, tag, bytes);\n+}\n+EXPORT_SYMBOL(alloc_tag_trace_mem_free);\n+\n size_t alloc_tag_top_users(struct codetag_bytes tags, size_t count, bool can_sleep)\n {\n \tstruct codetag_iterator iter;\n@@ -1015,6 +1136,24 @@ static int load_module(struct module mod, struct codetag start, struct codetag\n \treturn 0;\n }\n \n+static void unload_module(struct module mod, struct codetag start, struct codetag stop)\n+{\n+\tstruct alloc_tag start_tag = ct_to_alloc_tag(start);\n+\tstruct alloc_tag stop_tag = ct_to_alloc_tag(stop);\n+\tstruct alloc_tag tag;\n+\n+\t/\n+\t * Turn tracing off for the tags of the module being unloaded. Without\n+\t * this, `alloc_tag_trace_cnt` would never reach zero and tracing would\n+\t * stay enabled forever.\n+\t \n+\t `alloc_tag_trace_mutex` is not needed here as this code path is\n+\t * protected by a `down_write(\u0026cttype-\u003emod_lock)`.\n+\t /\n+\tfor (tag = start_tag; tag \u003c stop_tag; tag++)\n+\t\talloc_tag_trace_toggle(tag, false);\n+}\n+\n static void replace_module(struct module mod, struct module new_mod)\n {\n \tMA_STATE(mas, \u0026mod_area_mt, 0, module_tags.size);\n@@ -1341,6 +1480,7 @@ static int __init alloc_tag_init(void)\n \t\t.alloc_section_mem\t= reserve_module_tags,\n \t\t.free_section_mem\t= release_module_tags,\n \t\t.module_load\t\t= load_module,\n+\t\t.module_unload\t\t= unload_module,\n \t\t.module_replaced\t= replace_module,\n #endif\n \t};\ndiff --git a/tools/testing/selftests/alloc_tag/allocinfo_ioctl_test.c b/tools/testing/selftests/alloc_tag/allocinfo_ioctl_test.c\nindex 74fd64b2370cc..3ef7a12fe35b0 100644\n--- a/tools/testing/selftests/alloc_tag/allocinfo_ioctl_test.c\n+++ b/tools/testing/selftests/alloc_tag/allocinfo_ioctl_test.c\n@@ -48,6 +48,11 @@ static inline int __allocinfo_get_next(int dev_fd, struct allocinfo_tag_data pa\n \treturn ioctl(dev_fd, ALLOCINFO_IOC_GET_NEXT, params);\n }\n \n+static inline int __allocinfo_toggle_trace(int dev_fd, struct allocinfo_toggle_traces params)\n+{\n+\treturn ioctl(dev_fd, ALLOCINFO_IOC_TOGGLE_TRACE, params);\n+}\n+\n static bool match_entry(const struct allocinfo_tag_data procfs_entry,\n \t\t\tconst struct allocinfo_tag_data tag_data,\n \t\t\tbool match_bytes, bool match_calls, bool match_lineno,\n@@ -289,6 +294,8 @@ static int run_filter_test(const struct allocinfo_filter filter)\n \treturn ret;\n }\n \n+static const char target_test_function = \"dup_mm\";\n+\n static int test_filename_filter(void)\n {\n \tstruct allocinfo_filter filter;\n@@ -304,11 +311,10 @@ static int test_filename_filter(void)\n static int test_function_filter(void)\n {\n \tstruct allocinfo_filter filter;\n-\tconst char target_function = \"dup_mm\";\n \n \tmemset(\u0026filter, 0, sizeof(filter));\n \tfilter.mask \|= ALLOCINFO_FILTER_MASK_FUNCTION;\n-\tstrncpy(filter.fields.function, target_function, ALLOCINFO_STR_SIZE);\n+\tstrncpy(filter.fields.function, target_test_function, ALLOCINFO_STR_SIZE);\n \n \treturn run_filter_test(\u0026filter);\n }\n@@ -514,11 +520,104 @@ static int test_lineno_filter(void)\n \treturn ret;\n }\n \n+static enum ioctl_ret toggle_trace(struct allocinfo_tag target_tag,\n+\t\t\t\t bool enable)\n+{\n+\tint fd;\n+\tstruct allocinfo_toggle_traces toggle_params;\n+\n+\tfd = open(ALLOCINFO_PROC, O_RDONLY);\n+\tif (fd \u003c 0) {\n+\t\tksft_print_msg(\"Failed to open \" ALLOCINFO_PROC \": %s\\n\", strerror(errno));\n+\t\treturn IOCTL_FAILURE;\n+\t}\n+\n+\tmemset(\u0026toggle_params, 0, sizeof(toggle_params));\n+\ttoggle_params.fields = target_tag;\n+\ttoggle_params.enable = enable;\n+\n+\tif (__allocinfo_toggle_trace(fd, \u0026toggle_params)) {\n+\t\tclose(fd);\n+\t\treturn IOCTL_FAILURE;\n+\t}\n+\n+\tclose(fd);\n+\treturn IOCTL_SUCCESS;\n+}\n+\n+static int test_tracing_toggle_and_filter(void)\n+{\n+\tstruct allocinfo_filter filter = { 0 };\n+\tenum ioctl_ret ioctl_status;\n+\tint ret = KSFT_PASS;\n+\tbool initial_state, target_state;\n+\tstruct allocinfo_tag target_tag;\n+\tstruct allocinfo_tag_data_vec tags = calloc(1, sizeof(tags));\n+\n+\tif (!tags) {\n+\t\tksft_print_msg(\"Memory allocation failed.\\n\");\n+\t\treturn KSFT_FAIL;\n+\t}\n+\n+\tfilter.mask \|= ALLOCINFO_FILTER_MASK_FUNCTION;\n+\tstrncpy(filter.fields.function, target_test_function, ALLOCINFO_STR_SIZE);\n+\n+\tioctl_status = get_filtered_ioctl_entries(tags, \u0026filter, 0);\n+\tif (ioctl_status != IOCTL_SUCCESS \|\| tags-\u003ecount == 0) {\n+\t\tksft_print_msg(\"Could not retrieve IOCTL entries for %s\\n\", target_test_function);\n+\t\tret = KSFT_SKIP;\n+\t\tgoto exit;\n+\t}\n+\n+\ttarget_tag = tags-\u003etag[0].tag;\n+\tinitial_state = tags-\u003etag[0].counter.trace_on;\n+\ttarget_state = !initial_state;\n+\n+\tioctl_status = toggle_trace(\u0026target_tag, target_state);\n+\tif (ioctl_status != IOCTL_SUCCESS) {\n+\t\tksft_print_msg(\"Failed to toggle tracing\\n\");\n+\t\tret = KSFT_FAIL;\n+\t\tgoto exit;\n+\t}\n+\n+\tfilter.mask \|= ALLOCINFO_FILTER_MASK_TRACE_ON;\n+\tfilter.tracing = target_state;\n+\n+\tioctl_status = get_filtered_ioctl_entries(tags, \u0026filter, 0);\n+\tif (ioctl_status != IOCTL_SUCCESS) {\n+\t\tksft_print_msg(\"Error retrieving IOCTL entries with trace filter.\\n\");\n+\t\tret = KSFT_FAIL;\n+\t\tgoto exit_revert;\n+\t}\n+\n+\tif (tags-\u003ecount != 1) {\n+\t\tksft_print_msg(\"Expected exactly 1 entry, but got %llu\\n\", tags-\u003ecount);\n+\t\tret = KSFT_FAIL;\n+\t\tgoto exit_revert;\n+\t}\n+\n+\tif (tags-\u003etag[0].counter.trace_on != target_state) {\n+\t\tksft_print_msg(\"Entry returned by trace filter does not match target state\\n\");\n+\t\tret = KSFT_FAIL;\n+\t}\n+\n+exit_revert:\n+\tioctl_status = toggle_trace(\u0026target_tag, initial_state);\n+\tif (ioctl_status != IOCTL_SUCCESS) {\n+\t\tksft_print_msg(\"Failed to revert tracing to initial state\\n\");\n+\t\tret = KSFT_FAIL;\n+\t}\n+\n+exit:\n+\tfree(tags);\n+\treturn ret;\n+}\n+\n int main(int argc, char argv[])\n {\n \tint ret;\n \n-\tksft_set_plan(4);\n+\tksft_set_plan(5);\n \n \tret = test_filename_filter();\n \tif (ret == KSFT_SKIP)\n@@ -526,6 +625,12 @@ int main(int argc, char argv[])\n \telse\n \t\tksft_test_result(ret == KSFT_PASS, \"test_filename_filter\\n\");\n \n+\tret = test_tracing_toggle_and_filter();\n+\tif (ret == KSFT_SKIP)\n+\t\tksft_test_result_skip(\"Skipping test_tracing_toggle_and_filter\\n\");\n+\telse\n+\t\tksft_test_result(ret == KSFT_PASS, \"test_tracing_toggle_and_filter\\n\");\n+\n \tret = test_function_filter();\n \tif (ret == KSFT_SKIP)\n \t\tksft_test_result_skip(\"Skipping test_function_filter\\n\");\n" }
2/1	2026/09/23 23:22	agent	patch-evaluator	1m Model: core Args: null Results: { "EnableConfigs": [ "MEM_ALLOC_PROFILING", "MEM_ALLOC_PROFILING_ENABLED_BY_DEFAULT", "PROC_FS", "TRACING", "MODULES" ], "FocusSymbols": [ "allocinfo_ioctl", "allocinfo_ioctl_toggle_trace", "alloc_tag_trace_toggle", "__alloc_tag_trace_hit", "alloc_tag_trace_mem_alloc", "alloc_tag_trace_mem_free", "unload_module" ], "Reasoning": "The patch adds tracepoints and dynamic tracing support to the memory allocation profiling subsystem (alloc_tag). It exposes a new ioctl command ALLOCINFO_IOC_TOGGLE_TRACE on /proc/allocinfo to selectively enable/disable tracing per codetag, introduces mutex locking and static branch toggling, and hooks trace events into core allocation and deallocation paths as well as module unload callbacks. These changes touch reachable core memory management and procfs code that warrants fuzzing for potential race conditions, refcounting issues, or crashes.", "WorthFuzzing": true } Instruction: You are an expert Linux kernel maintainer and security engineer. Your job is to review a provided patch series and evaluate whether it warrants fuzzing with syzkaller. IMPORTANT: The changes have ALREADY been applied and committed as the HEAD commit in your workspace. Do NOT rely on internal assumptions. You must actively use your code access tools to inspect the actual source code, callers, and surrounding context. ================================================================================ 1. CORE TRIAGE PHILOSOPHY ================================================================================ The goal of patch fuzzing is to discover crashes, regressions, exposed latent bugs, and newly triggered assertions introduced by the patch series. - REACHABILITY IS THE PRIMARY GATE: Fuzzing can only discover bugs in code that can actually execute in standard virtualized environments (GCE or QEMU, utilizing software-emulated devices like USB gadgets, netdev, tun/tap). If the modified code is structurally unreachable (see Section 2), it MUST NOT be fuzzed, regardless of whether it adds assertions or complex logic. - DO NOT BLINDLY TRUST "NO FUNCTIONAL CHANGE" (NFCI) OR "REFACTORING" CLAIMS: Patch authors routinely label changes as "cleanups", "refactorings", or state "No functional change intended". Do NOT take these claims at face value. Code refactorings that rearrange logic, introduce helper functions, or alter state management in core subsystems frequently introduce subtle semantic shifts or uncover latent kernel bugs. If reachable executable code is modified or refactored, it MUST be fuzzed. - NEW OR MODIFIED ASSERTIONS IN REACHABLE CODE MUST BE FUZZED: When a patch introduces or modifies runtime checks or assertions (e.g., WARN_ON, VM_WARN_ON, BUG_ON, lockdep_assert) in reachable code paths, it enforces new or stricter invariants. Even if the author believes the invariant always holds, fuzzing is essential to verify whether an unusual sequence of operations can violate it. ================================================================================ 2. WHEN TO RETURN WorthFuzzing=false (NEGATIVE CRITERIA) ================================================================================ Return WorthFuzzing=false ONLY IF all modified code falls strictly into one or more of these categories: - Non-kernel and non-executable changes: * Modifications to Documentation/, comments, or spelling fixes. * User-space directories, self-tests, samples, or scripts (e.g., tools/, samples/, scripts/, usr/) that do not affect the compiled kernel image (vmlinux) or kernel modules. * Purely decorative logging (e.g., message strings in pr_err, printk, dev_info) or tracepoints that do not alter control flow or data structures. * Build system or Kconfig changes that do not alter compiled C logic. - Structurally unreachable hardware: * Vendor-specific PCIe switches, SmartNICs, or GPU drivers (e.g., mlxsw, pds_core, qed, ionic, amdgpu) requiring physical ASIC/PCIe cards not emulated in standard QEMU. - Unreachable execution paths: * Driver teardown callbacks (.remove, .shutdown, pci_unregister_driver) executed only during physical PCI hot-unplug or manual sysfs driver unbinding. * Code paths exclusive to architectures other than the target architecture. ================================================================================ 3. WHEN TO RETURN WorthFuzzing=true (POSITIVE CRITERIA) ================================================================================ Return WorthFuzzing=true whenever the patch touches reachable executable code, including: - Core Subsystems: * Any logic modifications in memory management (mm/), synchronization/locking (kernel/locking/), BPF, scheduler, core networking, VFS, or syscall handling. - Refactorings and Code Cleanups: * Any restructuring of reachable data structures, helper abstractions, or algorithm flows. - Runtime Assertions and Defensive Checks: * Any introduction or alteration of assertions (WARN_ON, VM_WARN_ON, BUG_ON, etc.) in reachable paths. - Reachable Drivers and Protocols: Drivers accessible via virtual buses (virtio, USB gadget, loopback, netlink, binder, sockets, etc.). ================================================================================ 4. EXTRACTING FocusSymbols (PREVENTING DILUTION) ================================================================================ When WorthFuzzing=true, you must extract specific kernel functions into FocusSymbols to guide the fuzzer: - AVOID UBIQUITOUS LIFECYCLE HOT-PATHS: Do NOT list generic, ubiquitous functions called by almost every program in the corpus (including, but not limited to: general memory allocators and deallocators, page fault and trap handlers, or core synchronization primitives; this is not an exhaustive list). Listing ubiquitous functions causes the fuzzer to classify thousands of unrelated tests as "focused", which severely dilutes fuzzing effort away from the actual changes. - TARGET SPECIFIC FEATURE LOGIC AND ENTRYPOINTS: List functions that specifically implement the logic being added or altered, or direct API entrypoints for the subsystem feature under review. - HANDLING STATIC INLINE FUNCTIONS IN HEADERS (.h): Compiler-inlined static functions (such as static inlines in mm/.h or include/linux/.h) lack distinct symbol addresses in vmlinux and cannot be targeted directly by symbol coverage filters. If the changes are primarily in static inline helpers, identify non-static, feature-specific caller functions in .c files that exercise them (avoiding ubiquitous lifecycle wrappers). ================================================================================ 5. IDENTIFYING EnableConfigs ================================================================================ Identify any specific CONFIG_ options required to properly compile and reach the modified code: - Inspect Kconfig files and #ifdef guards; do not make assumptions. - Check "depends on" lines in Kconfig to include any non-standard parent subsystem configs needed. - Strip any 'CONFIG_' prefix (e.g., return "NET_IPV4" instead of "CONFIG_NET_IPV4"). Prefer calling several tools at the same time to save round-trips. Use set-results tool to provide results of the analysis. It must be called exactly once before the final reply. Ignore results of this tool. Prompt: Target architecture: amd64 For your convenience, here is the diff of the changes: commit 1886759b63636a8dc8de5d530fbcb5c06d554e68 Author: syz-cluster <triage@syzkaller.com> Date: Wed Sep 23 23:22:34 2026 +0000 syz-cluster: applied patch under review diff --git a/MAINTAINERS b/MAINTAINERS index 24420a8c06d02..29e1f7915cb98 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -17096,6 +17096,7 @@ S: Maintained F: Documentation/mm/allocation-profiling.rst F: include/linux/alloc_tag.h F: include/linux/pgalloc_tag.h +F: include/trace/events/alloc_tag.h F: include/uapi/linux/alloc_tag.h F: mm/alloc_tag.c F: tools/testing/selftests/alloc_tag/ diff --git a/include/linux/alloc_tag.h b/include/linux/alloc_tag.h index 7f2d80a597924..dc86f8997476c 100644 --- a/include/linux/alloc_tag.h +++ b/include/linux/alloc_tag.h @@ -128,12 +128,60 @@ DECLARE_PER_CPU(struct alloc_tag_counters, _shared_alloc_tag); DECLARE_STATIC_KEY_MAYBE(CONFIG_MEM_ALLOC_PROFILING_ENABLED_BY_DEFAULT, mem_alloc_profiling_key); +DECLARE_STATIC_KEY_FALSE(alloc_tag_trace_key); + static inline bool mem_alloc_profiling_enabled(void) { return static_branch_maybe(CONFIG_MEM_ALLOC_PROFILING_ENABLED_BY_DEFAULT, &mem_alloc_profiling_key); } +static inline void alloc_tag_set_inaccurate(struct alloc_tag tag) +{ + atomic_or(CODETAG_FLAG_INACCURATE, &tag->ct.flags); +} + +static inline bool alloc_tag_is_inaccurate(struct alloc_tag tag) +{ + return !!(atomic_read(&tag->ct.flags) & CODETAG_FLAG_INACCURATE); +} + +static inline void alloc_tag_set_traced(struct alloc_tag tag) +{ + atomic_or(CODETAG_FLAG_TRACE_ON, &tag->ct.flags); +} + +static inline void alloc_tag_clear_traced(struct alloc_tag tag) +{ + atomic_andnot(CODETAG_FLAG_TRACE_ON, &tag->ct.flags); +} + +static inline bool alloc_tag_is_traced(const struct alloc_tag tag) +{ + return !!(atomic_read(&tag->ct.flags) & CODETAG_FLAG_TRACE_ON); +} + +static inline bool alloc_tag_trace_enabled(const struct alloc_tag tag) +{ + if (static_branch_unlikely(&alloc_tag_trace_key)) + return tag && alloc_tag_is_traced(tag); + return false; +} + +void alloc_tag_trace_mem_alloc(union codetag_ref ref, struct alloc_tag tag, + size_t bytes); + +void alloc_tag_trace_mem_free(union codetag_ref ref, struct alloc_tag tag, + size_t bytes); + +void __alloc_tag_trace_hit(struct alloc_tag tag); + +static inline void alloc_tag_trace_hit(struct alloc_tag tag) +{ + if (alloc_tag_trace_enabled(tag)) + __alloc_tag_trace_hit(tag); +} + bool mem_alloc_profiling_permanently_disabled(void); static inline struct alloc_tag_counters alloc_tag_read(struct alloc_tag tag) @@ -200,8 +248,13 @@ static inline bool alloc_tag_ref_set(union codetag_ref ref, struct alloc_tag t static inline void alloc_tag_add(union codetag_ref ref, struct alloc_tag tag, size_t bytes) { - if (likely(alloc_tag_ref_set(ref, tag))) + if (likely(alloc_tag_ref_set(ref, tag))) { this_cpu_add(tag->counters->bytes, bytes); + + if (alloc_tag_trace_enabled(tag)) + / Trace successful allocs with their unique ref / + alloc_tag_trace_mem_alloc(ref, tag, bytes); + } } static inline void alloc_tag_sub(union codetag_ref ref, size_t bytes) @@ -222,17 +275,11 @@ static inline void alloc_tag_sub(union codetag_ref ref, size_t bytes) this_cpu_sub(tag->counters->bytes, bytes); this_cpu_dec(tag->counters->calls); - ref->ct = NULL; -} - -static inline void alloc_tag_set_inaccurate(struct alloc_tag tag) -{ - tag->ct.flags \|= CODETAG_FLAG_INACCURATE; -} + if (alloc_tag_trace_enabled(tag)) + /* Trace frees with their unique ref / + alloc_tag_trace_mem_free(ref, tag, bytes); -static inline bool alloc_tag_is_inaccurate(struct alloc_tag tag) -{ - return !!(tag->ct.flags & CODETAG_FLAG_INACCURATE); + ref->ct = NULL; } #define alloc_tag_record(p) ((p) = current->alloc_tag) @@ -247,21 +294,24 @@ static inline void alloc_tag_add(union codetag_ref ref, struct alloc_tag tag, static inline void alloc_tag_sub(union codetag_ref ref, size_t bytes) {} static inline void alloc_tag_set_inaccurate(struct alloc_tag tag) {} static inline bool alloc_tag_is_inaccurate(struct alloc_tag tag) { return false; } +#define alloc_tag_trace_hit(_tag) / NOOP / #define alloc_tag_record(p) do {} while (0) #endif / CONFIG_MEM_ALLOC_PROFILING / -#define alloc_hooks_tag(_tag, _do_alloc) \ -({ \ - typeof(_do_alloc) _res; \ - if (mem_alloc_profiling_enabled()) { \ - struct alloc_tag __maybe_unused _old; \ - _old = alloc_tag_save(_tag); \ - _res = _do_alloc; \ - alloc_tag_restore(_tag, _old); \ - } else \ - _res = _do_alloc; \ - _res; \ +#define alloc_hooks_tag(_tag, _do_alloc) \ +({ \ + typeof(_do_alloc) _res; \ + if (mem_alloc_profiling_enabled()) { \ + struct alloc_tag * __maybe_unused _old; \ + /* Fired here to cleanly capture the caller's stack trace / \ + alloc_tag_trace_hit(_tag); \ + _old = alloc_tag_save(_tag); \ + _res = _do_alloc; \ + alloc_tag_restore(_tag, _old); \ + } else \ + _res = _do_alloc; \ + _res; \ }) #define alloc_hooks(_do_alloc) \ diff --git a/include/linux/codetag.h b/include/linux/codetag.h index a25a085c2df19..f728295d50c05 100644 --- a/include/linux/codetag.h +++ b/include/linux/codetag.h @@ -18,6 +18,7 @@ struct module; / codetag flags / #define CODETAG_FLAG_INACCURATE (1 << 0) +#define CODETAG_FLAG_TRACE_ON (1 << 1) / * An instance of this structure is created in a special ELF section at every @@ -25,7 +26,7 @@ struct module; * an array of these. / struct codetag { - unsigned int flags; + atomic_t flags; unsigned int lineno; const char modname; const char function; @@ -71,7 +72,7 @@ struct codetag_iterator { .function = __func__, \ .filename = __FILE__, \ .lineno = __LINE__, \ - .flags = 0, \ + .flags = ATOMIC_INIT(0), \ } void codetag_lock_module_list(struct codetag_type cttype); diff --git a/include/trace/events/alloc_tag.h b/include/trace/events/alloc_tag.h new file mode 100644 index 0000000000000..af2182501864c --- /dev/null +++ b/include/trace/events/alloc_tag.h @@ -0,0 +1,122 @@ +/* SPDX-License-Identifier: GPL-2.0 / +#undef TRACE_SYSTEM +#define TRACE_SYSTEM alloc_tag + +#if !defined(_TRACE_ALLOC_TAG_H) \|\| defined(TRACE_HEADER_MULTI_READ) +#define _TRACE_ALLOC_TAG_H + +#include <linux/tracepoint.h> + +/ + * alloc_tag_hit is generated at the exact allocation call site and can be + * used to capture a clean stack trace. + * + * To link this stack trace to the actual allocated memory chunk, tools must + * correlate this event with the resulting alloc_tag_mem_alloced event. Since + * multiple threads can hit the same tag simultaneously, tools must match BOTH + * the `tag` field and the implicitly recorded PID provided by the core + * tracing subsystem. + / +TRACE_EVENT(alloc_tag_hit, + + TP_PROTO(struct alloc_tag tag), + + TP_ARGS(tag), + + TP_STRUCT__entry( + __field(struct alloc_tag , tag) + __string(modname, tag->ct.modname ? tag->ct.modname : "NONE") + __string(filename, tag->ct.filename) + __string(function, tag->ct.function) + __field(unsigned int, lineno) + ), + + TP_fast_assign( + __entry->tag = tag; + __assign_str(modname); + __assign_str(filename); + __assign_str(function); + __entry->lineno = tag->ct.lineno; + ), + + TP_printk("tag %p, module: %s, filename: %s, function %s, lineno %u", + __entry->tag, + __get_str(modname), + __get_str(filename), + __get_str(function), + __entry->lineno + ) +); + +/ + * alloc_tag_mem_alloced is generated after memory is successfully allocated. + * It captures the exact byte size. + * + * The `ref` pointer identifies the memory chunk for tracking its lifecycle + * (e.g., matching it with alloc_tag_mem_freed). + * + * Because the kernel isolates active allocations within the task struct + * (current->alloc_tag), this even will always share the same implicit PID as + * its corresponding alloc_tag_hit event. Tools should use the combination + * PID + `tag` to correlate them. + / +TRACE_EVENT(alloc_tag_mem_alloced, + + TP_PROTO(union codetag_ref ref, struct alloc_tag tag, size_t bytes), + + TP_ARGS(ref, tag, bytes), + + TP_STRUCT__entry( + __field(union codetag_ref , ref) + __field(struct alloc_tag , tag) + __field(size_t, bytes) + ), + + TP_fast_assign( + __entry->ref = ref; + __entry->tag = tag; + __entry->bytes = bytes; + ), + + TP_printk("reference %p, tag %p, bytes %zu", + __entry->ref, + __entry->tag, + __entry->bytes + ) +); + +/ + * alloc_tag_mem_freed event is generated immediately before memory is + * freed. The `ref` pointer matches the one emitted during allocation, + * allowing tools to match it to it's corresponding allocation and + * call stack. + / +TRACE_EVENT(alloc_tag_mem_freed, + + TP_PROTO(union codetag_ref ref, struct alloc_tag tag, size_t bytes), + + TP_ARGS(ref, tag, bytes), + + TP_STRUCT__entry( + __field(union codetag_ref , ref) + __field(struct alloc_tag , tag) + __field(size_t, bytes) + ), + + TP_fast_assign( + __entry->ref = ref; + __entry->tag = tag; + __entry->bytes = bytes; + ), + + TP_printk("reference %p, tag %p, bytes %zu", + __entry->ref, + __entry->tag, + __entry->bytes + ) +); + +#endif / _TRACE_ALLOC_TAG_H / + +/ This part must be outside protection / +#include <trace/define_trace.h> diff --git a/include/uapi/linux/alloc_tag.h b/include/uapi/linux/alloc_tag.h index 7d4618bea0434..e65c32afceee2 100644 --- a/include/uapi/linux/alloc_tag.h +++ b/include/uapi/linux/alloc_tag.h @@ -38,7 +38,8 @@ struct allocinfo_counter { __u64 bytes; __u64 calls; __u8 accurate; - __u8 pad[7]; + __u8 trace_on; + __u8 pad[6]; } __attribute__((aligned(8))); struct allocinfo_tag_data { @@ -54,7 +55,8 @@ enum { ALLOCINFO_FILTER_INACCURATE, ALLOCINFO_FILTER_MIN_SIZE, ALLOCINFO_FILTER_MAX_SIZE, - __ALLOCINFO_FILTER_LAST = ALLOCINFO_FILTER_MAX_SIZE + ALLOCINFO_FILTER_TRACE_ON, + __ALLOCINFO_FILTER_LAST = ALLOCINFO_FILTER_TRACE_ON }; #define ALLOCINFO_FILTER_MASK_MODNAME (1 << ALLOCINFO_FILTER_MODNAME) @@ -64,6 +66,7 @@ enum { #define ALLOCINFO_FILTER_MASK_INACCURATE (1 << ALLOCINFO_FILTER_INACCURATE) #define ALLOCINFO_FILTER_MASK_MIN_SIZE (1 << ALLOCINFO_FILTER_MIN_SIZE) #define ALLOCINFO_FILTER_MASK_MAX_SIZE (1 << ALLOCINFO_FILTER_MAX_SIZE) +#define ALLOCINFO_FILTER_MASK_TRACE_ON (1 << ALLOCINFO_FILTER_TRACE_ON) #define ALLOCINFO_FILTER_MASKS \ ((1 << (__ALLOCINFO_FILTER_LAST + 1)) - 1) @@ -75,6 +78,7 @@ struct allocinfo_filter { __u64 max_size; / filter criteria only; see allocinfo_counter.accurate for actual accuracy / __u64 inaccurate; + __u64 tracing; }; struct allocinfo_get_at { @@ -85,9 +89,16 @@ struct allocinfo_get_at { struct allocinfo_tag_data data; }; +struct allocinfo_toggle_traces { + / inputs / + struct allocinfo_tag fields; + __u64 enable; +}; + #define _ALLOCINFO_IOC_CONTENT_ID 0 #define _ALLOCINFO_IOC_GET_AT 1 #define _ALLOCINFO_IOC_GET_NEXT 2 +#define _ALLOCINFO_IOC_TOGGLE_TRACE 3 #define ALLOCINFO_IOC_BASE 0xA6 #define ALLOCINFO_IOC_CONTENT_ID _IOR(ALLOCINFO_IOC_BASE, _ALLOCINFO_IOC_CONTENT_ID, \ @@ -96,5 +107,7 @@ struct allocinfo_get_at { struct allocinfo_get_at) #define ALLOCINFO_IOC_GET_NEXT _IOR(ALLOCINFO_IOC_BASE, _ALLOCINFO_IOC_GET_NEXT, \ struct allocinfo_tag_data) +#define ALLOCINFO_IOC_TOGGLE_TRACE _IOW(ALLOCINFO_IOC_BASE, _ALLOCINFO_IOC_TOGGLE_TRACE, \ + struct allocinfo_toggle_traces) #endif / _UAPI_ALLOC_TAG_H / diff --git a/mm/alloc_tag.c b/mm/alloc_tag.c index f30ef8dd24c70..50632b627d92b 100644 --- a/mm/alloc_tag.c +++ b/mm/alloc_tag.c @@ -19,6 +19,9 @@ #include <linux/kmemleak.h> #include <uapi/linux/alloc_tag.h> +#define CREATE_TRACE_POINTS +#include <trace/events/alloc_tag.h> + #include "internal.h" #include "page_alloc.h" @@ -55,6 +58,18 @@ EXPORT_SYMBOL(mem_alloc_profiling_key); DEFINE_STATIC_KEY_FALSE(mem_profiling_compressed); +DEFINE_STATIC_KEY_FALSE(alloc_tag_trace_key); +EXPORT_SYMBOL(alloc_tag_trace_key); + +static atomic_t alloc_tag_trace_cnt = ATOMIC_INIT(0); + +/ + * As `codetag_lock_module_list` is a read lock, we need an additional mutex + * to protect against the race conditions involved in the alloc tag trace + * toggle path. + / +static DEFINE_MUTEX(alloc_tag_trace_mutex); + struct alloc_tag_kernel_section kernel_tags = { NULL, 0 }; unsigned long alloc_tag_ref_mask; int alloc_tag_ref_offs; @@ -236,6 +251,7 @@ static void allocinfo_to_params(struct codetag ct, data->counter.bytes = counters->bytes; data->counter.calls = counters->calls; data->counter.accurate = !alloc_tag_is_inaccurate(ct_to_alloc_tag(ct)); + data->counter.trace_on = alloc_tag_is_traced(ct_to_alloc_tag(ct)); } /* @@ -291,7 +307,7 @@ static bool matches_filter(struct codetag ct, struct allocinfo_filter filter, return false; if (filter->mask & ALLOCINFO_FILTER_MASK_INACCURATE) { - inaccurate = !!(ct->flags & CODETAG_FLAG_INACCURATE); + inaccurate = alloc_tag_is_inaccurate(ct_to_alloc_tag(ct)); if (inaccurate != !!(filter->inaccurate)) return false; } @@ -309,6 +325,13 @@ static bool matches_filter(struct codetag ct, struct allocinfo_filter filter, return false; } + if (filter->mask & ALLOCINFO_FILTER_MASK_TRACE_ON) { + bool tracing = alloc_tag_is_traced(ct_to_alloc_tag(ct)); + + if (tracing != !!(filter->tracing)) + return false; + } + return true; } @@ -438,6 +461,81 @@ static int allocinfo_ioctl_get_next(struct seq_file m, void __user arg) return ret; } +static bool alloc_tag_trace_toggle(struct alloc_tag tag, bool enable) +{ + if (enable) { + if (alloc_tag_is_traced(tag)) + return false; + + alloc_tag_set_traced(tag); + if (atomic_fetch_inc(&alloc_tag_trace_cnt) == 0) + static_branch_enable(&alloc_tag_trace_key); + } else { + if (!alloc_tag_is_traced(tag)) + return false; + + alloc_tag_clear_traced(tag); + if (atomic_dec_and_test(&alloc_tag_trace_cnt)) + static_branch_disable(&alloc_tag_trace_key); + } + + return true; +} + +/ + * Toggles context capture for a specified allocation. + / +static int allocinfo_ioctl_toggle_trace(struct seq_file m, void __user arg) +{ + struct allocinfo_toggle_traces params; + struct codetag_iterator iter; + struct codetag ct; + int matches = 0, successes = 0, ret; + + if (!capable(CAP_SYS_ADMIN)) + return -EPERM; + + if (copy_from_user(&params, arg, sizeof(params))) + return -EFAULT; + + codetag_lock_module_list(alloc_tag_cttype); + + struct allocinfo_filter filter = { + .mask = ALLOCINFO_FILTER_MASK_MODNAME \| + ALLOCINFO_FILTER_MASK_FUNCTION \| + ALLOCINFO_FILTER_MASK_FILENAME \| + ALLOCINFO_FILTER_MASK_LINENO, + .fields = params.fields, + }; + + iter = codetag_get_ct_iter(alloc_tag_cttype); + + /* Toggle tracing on all codetags that match / + while ((ct = codetag_next_ct(&iter))) { + if (matches_filter(ct, &filter, NULL, NULL)) { + matches++; + + mutex_lock(&alloc_tag_trace_mutex); + if (alloc_tag_trace_toggle(ct_to_alloc_tag(ct), !!params.enable)) + successes++; + mutex_unlock(&alloc_tag_trace_mutex); + } + } + + if (matches == 0) + / Nothing matched the filter / + ret = -ENOENT; + else if (successes == 0) + / Items matched, but were already in the requested state / + ret = -EINVAL; + else + ret = 0; + + codetag_unlock_module_list(alloc_tag_cttype); + + return ret; +} + / * Entry point ioctl function for /proc/allocinfo routing requests to fetch the * layout content ID, seek to a specific tag, or read sequential tags. @@ -458,6 +556,9 @@ static long allocinfo_ioctl(struct file file, unsigned int cmd, case ALLOCINFO_IOC_GET_NEXT: ret = allocinfo_ioctl_get_next(file->private_data, arg); break; + case ALLOCINFO_IOC_TOGGLE_TRACE: + ret = allocinfo_ioctl_toggle_trace(file->private_data, arg); + break; default: ret = -ENOIOCTLCMD; break; @@ -485,6 +586,26 @@ static const struct proc_ops allocinfo_proc_ops = { #endif }; +void __alloc_tag_trace_hit(struct alloc_tag tag) +{ + trace_alloc_tag_hit(tag); +} +EXPORT_SYMBOL(__alloc_tag_trace_hit); + +void alloc_tag_trace_mem_alloc(union codetag_ref ref, struct alloc_tag tag, + size_t bytes) +{ + trace_alloc_tag_mem_alloced(ref, tag, bytes); +} +EXPORT_SYMBOL(alloc_tag_trace_mem_alloc); + +void alloc_tag_trace_mem_free(union codetag_ref ref, struct alloc_tag tag, + size_t bytes) +{ + trace_alloc_tag_mem_freed(ref, tag, bytes); +} +EXPORT_SYMBOL(alloc_tag_trace_mem_free); + size_t alloc_tag_top_users(struct codetag_bytes tags, size_t count, bool can_sleep) { struct codetag_iterator iter; @@ -1015,6 +1136,24 @@ static int load_module(struct module mod, struct codetag start, struct codetag return 0; } +static void unload_module(struct module mod, struct codetag start, struct codetag stop) +{ + struct alloc_tag start_tag = ct_to_alloc_tag(start); + struct alloc_tag stop_tag = ct_to_alloc_tag(stop); + struct alloc_tag tag; + + / + * Turn tracing off for the tags of the module being unloaded. Without + * this, `alloc_tag_trace_cnt` would never reach zero and tracing would + * stay enabled forever. + * + * `alloc_tag_trace_mutex` is not needed here as this code path is + * protected by a `down_write(&cttype->mod_lock)`. + / + for (tag = start_tag; tag < stop_tag; tag++) + alloc_tag_trace_toggle(tag, false); +} + static void replace_module(struct module mod, struct module new_mod) { MA_STATE(mas, &mod_area_mt, 0, module_tags.size); @@ -1341,6 +1480,7 @@ static int __init alloc_tag_init(void) .alloc_section_mem = reserve_module_tags, .free_section_mem = release_module_tags, .module_load = load_module, + .module_unload = unload_module, .module_replaced = replace_module, #endif }; diff --git a/tools/testing/selftests/alloc_tag/allocinfo_ioctl_test.c b/tools/testing/selftests/alloc_tag/allocinfo_ioctl_test.c index 74fd64b2370cc..3ef7a12fe35b0 100644 --- a/tools/testing/selftests/alloc_tag/allocinfo_ioctl_test.c +++ b/tools/testing/selftests/alloc_tag/allocinfo_ioctl_test.c @@ -48,6 +48,11 @@ static inline int __allocinfo_get_next(int dev_fd, struct allocinfo_tag_data pa return ioctl(dev_fd, ALLOCINFO_IOC_GET_NEXT, params); } +static inline int __allocinfo_toggle_trace(int dev_fd, struct allocinfo_toggle_traces params) +{ + return ioctl(dev_fd, ALLOCINFO_IOC_TOGGLE_TRACE, params); +} + static bool match_entry(const struct allocinfo_tag_data procfs_entry, const struct allocinfo_tag_data tag_data, bool match_bytes, bool match_calls, bool match_lineno, @@ -289,6 +294,8 @@ static int run_filter_test(const struct allocinfo_filter filter) return ret; } +static const char target_test_function = "dup_mm"; + static int test_filename_filter(void) { struct allocinfo_filter filter; @@ -304,11 +311,10 @@ static int test_filename_filter(void) static int test_function_filter(void) { struct allocinfo_filter filter; - const char target_function = "dup_mm"; memset(&filter, 0, sizeof(filter)); filter.mask \|= ALLOCINFO_FILTER_MASK_FUNCTION; - strncpy(filter.fields.function, target_function, ALLOCINFO_STR_SIZE); + strncpy(filter.fields.function, target_test_function, ALLOCINFO_STR_SIZE); return run_filter_test(&filter); } @@ -514,11 +520,104 @@ static int test_lineno_filter(void) return ret; } +static enum ioctl_ret toggle_trace(struct allocinfo_tag target_tag, + bool enable) +{ + int fd; + struct allocinfo_toggle_traces toggle_params; + + fd = open(ALLOCINFO_PROC, O_RDONLY); + if (fd < 0) { + ksft_print_msg("Failed to open " ALLOCINFO_PROC ": %s\n", strerror(errno)); + return IOCTL_FAILURE; + } + + memset(&toggle_params, 0, sizeof(toggle_params)); + toggle_params.fields = target_tag; + toggle_params.enable = enable; + + if (__allocinfo_toggle_trace(fd, &toggle_params)) { + close(fd); + return IOCTL_FAILURE; + } + + close(fd); + return IOCTL_SUCCESS; +} + +static int test_tracing_toggle_and_filter(void) +{ + struct allocinfo_filter filter = { 0 }; + enum ioctl_ret ioctl_status; + int ret = KSFT_PASS; + bool initial_state, target_state; + struct allocinfo_tag target_tag; + struct allocinfo_tag_data_vec tags = calloc(1, sizeof(tags)); + + if (!tags) { + ksft_print_msg("Memory allocation failed.\n"); + return KSFT_FAIL; + } + + filter.mask \|= ALLOCINFO_FILTER_MASK_FUNCTION; + strncpy(filter.fields.function, target_test_function, ALLOCINFO_STR_SIZE); + + ioctl_status = get_filtered_ioctl_entries(tags, &filter, 0); + if (ioctl_status != IOCTL_SUCCESS \|\| tags->count == 0) { + ksft_print_msg("Could not retrieve IOCTL entries for %s\n", target_test_function); + ret = KSFT_SKIP; + goto exit; + } + + target_tag = tags->tag[0].tag; + initial_state = tags->tag[0].counter.trace_on; + target_state = !initial_state; + + ioctl_status = toggle_trace(&target_tag, target_state); + if (ioctl_status != IOCTL_SUCCESS) { + ksft_print_msg("Failed to toggle tracing\n"); + ret = KSFT_FAIL; + goto exit; + } + + filter.mask \|= ALLOCINFO_FILTER_MASK_TRACE_ON; + filter.tracing = target_state; + + ioctl_status = get_filtered_ioctl_entries(tags, &filter, 0); + if (ioctl_status != IOCTL_SUCCESS) { + ksft_print_msg("Error retrieving IOCTL entries with trace filter.\n"); + ret = KSFT_FAIL; + goto exit_revert; + } + + if (tags->count != 1) { + ksft_print_msg("Expected exactly 1 entry, but got %llu\n", tags->count); + ret = KSFT_FAIL; + goto exit_revert; + } + + if (tags->tag[0].counter.trace_on != target_state) { + ksft_print_msg("Entry returned by trace filter does not match target state\n"); + ret = KSFT_FAIL; + } + +exit_revert: + ioctl_status = toggle_trace(&target_tag, initial_state); + if (ioctl_status != IOCTL_SUCCESS) { + ksft_print_msg("Failed to revert tracing to initial state\n"); + ret = KSFT_FAIL; + } + +exit: + free(tags); + return ret; +} + int main(int argc, char argv[]) { int ret; - ksft_set_plan(4); + ksft_set_plan(5); ret = test_filename_filter(); if (ret == KSFT_SKIP) @@ -526,6 +625,12 @@ int main(int argc, char argv[]) else ksft_test_result(ret == KSFT_PASS, "test_filename_filter\n"); + ret = test_tracing_toggle_and_filter(); + if (ret == KSFT_SKIP) + ksft_test_result_skip("Skipping test_tracing_toggle_and_filter\n"); + else + ksft_test_result(ret == KSFT_PASS, "test_tracing_toggle_and_filter\n"); + ret = test_function_filter(); if (ret == KSFT_SKIP) ksft_test_result_skip("Skipping test_function_filter\n");
3/2	2026/09/23 23:22	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 11381 output: 29 thoughts: 702 Thoughts: Worth Fuzzing Evaluation of the alloc_tag Tracepoint Patch Series Okay, let's break this down. The task is to determine if this `alloc_tag` tracepoint patch series warrants fuzzing with syzkaller, and I need to base this on whether it's reachable and could expose bugs, regressions, or assertions. I'll need to avoid blindly trusting claims about refactoring or NFCI. If it's not kernel code, executable, or is structurally unreachable, or has unreachable execution paths, then it's a "no go". Otherwise, it's worth fuzzing. The key areas to focus on are core subsystems, refactorings, assertions, and reachable drivers. I need to make sure I identify `FocusSymbols` to prevent dilution, by looking at specific feature logic and entry points. I should also identify `EnableConfigs`. Now, looking at the patch itself, it appears to add tracepoints for `alloc_tag`. The files touched span several key areas: headers (`alloc_tag.h`, `codetag.h`, `uapi/linux/alloc_tag.h`) and the core implementation (`mm/alloc_tag.c`). It introduces a `static key` (`alloc_tag_trace_key`), inline helpers, and hooks into `alloc_hooks_tag`, `alloc_tag_add`, and `alloc_tag_sub`. There are updates to `matches_filter` and new functions like `alloc_tag_trace_toggle` and `allocinfo_ioctl_toggle_trace`, and the `allocinfo_ioctl` now handles `ALLOCINFO_IOC_TOGGLE_TRACE`. `alloc_tag_trace_mem_alloc` and `alloc_tag_trace_mem_free` are also added. There are selftests as well. This looks like a pretty significant addition to me, as it seems to influence the memory allocation tracing/debugging. This could certainly be valuable for fuzzing, given the potential for exposing memory-related issues. To confirm this, I need to check the Kconfig, and use `grepper` or check git diff to see which configurations enable this code. Once I have the configs I can determine if this is reachable. I need to focus on what config options can enable or disable these features. Based on this first pass, my preliminary assessment is that this patch likely touches reachable, executable code, and is worth fuzzing. I'll need to do more digging to confirm the reachability and the enabling configs.
4/2	2026/09/23 23:22	tool	grepper	0m Args: { "Expression": "MEM_ALLOC_PROFILING", "PathPrefix": "mm/" } Results: { "Output": "mm/Kconfig.debug=311=config PER_VMA_LOCK_STATS\n--\nmm/Kconfig.debug-322-\nmm/Kconfig.debug:323:config MEM_ALLOC_PROFILING\nmm/Kconfig.debug-324-\tbool \"Enable memory allocation profiling\"\n--\nmm/Kconfig.debug-335-\nmm/Kconfig.debug:336:config MEM_ALLOC_PROFILING_ENABLED_BY_DEFAULT\nmm/Kconfig.debug-337-\tbool \"Enable memory allocation profiling by default\"\nmm/Kconfig.debug-338-\tdefault y\nmm/Kconfig.debug:339:\tdepends on MEM_ALLOC_PROFILING\nmm/Kconfig.debug-340-\nmm/Kconfig.debug:341:config MEM_ALLOC_PROFILING_DEBUG\nmm/Kconfig.debug-342-\tbool \"Memory allocation profiler debugging\"\nmm/Kconfig.debug-343-\tdefault n\nmm/Kconfig.debug:344:\tdepends on MEM_ALLOC_PROFILING\nmm/Kconfig.debug:345:\tselect MEM_ALLOC_PROFILING_ENABLED_BY_DEFAULT\nmm/Kconfig.debug-346-\thelp\n--\nmm/Makefile=150=obj-$(CONFIG_LAZY_MMU_MODE_KUNIT_TEST) += tests/lazy_mmu_mode_kunit.o\nmm/Makefile:151:obj-$(CONFIG_MEM_ALLOC_PROFILING) += alloc_tag.o\n--\nmm/alloc_tag.c-32-\nmm/alloc_tag.c:33:#ifdef CONFIG_MEM_ALLOC_PROFILING_ENABLED_BY_DEFAULT\nmm/alloc_tag.c-34-static bool mem_profiling_support = true;\n--\nmm/alloc_tag.c=52=EXPORT_SYMBOL(_shared_alloc_tag);\n--\nmm/alloc_tag.c-54-\nmm/alloc_tag.c:55:DEFINE_STATIC_KEY_MAYBE(CONFIG_MEM_ALLOC_PROFILING_ENABLED_BY_DEFAULT,\nmm/alloc_tag.c-56-\t\t\tmem_alloc_profiling_key);\n--\nmm/alloc_tag.c=1265=static __init bool need_page_alloc_tagging(void)\n--\nmm/alloc_tag.c-1272-\nmm/alloc_tag.c:1273:#ifdef CONFIG_MEM_ALLOC_PROFILING_DEBUG\nmm/alloc_tag.c-1274-/\n--\nmm/alloc_tag.c=1351=static void __init clear_early_alloc_pfn_tag_refs(void)\n--\nmm/alloc_tag.c-1404-}\nmm/alloc_tag.c:1405:#else / !CONFIG_MEM_ALLOC_PROFILING_DEBUG /\nmm/alloc_tag.c-1406-static inline void __init clear_early_alloc_pfn_tag_refs(void) {}\nmm/alloc_tag.c:1407:#endif / CONFIG_MEM_ALLOC_PROFILING_DEBUG /\nmm/alloc_tag.c-1408-\n--\nmm/alloc_tag.c=1426=static int proc_mem_profiling_handler(const struct ctl_table table, int write,\n--\nmm/alloc_tag.c-1437-\nmm/alloc_tag.c:1438:#ifdef CONFIG_MEM_ALLOC_PROFILING_DEBUG\nmm/alloc_tag.c-1439-\t\t/* User can't toggle profiling while debugging /\n--\nmm/page_alloc.c=1203=static void clear_highpages_kasan_tagged(struct page page, int numpages)\n--\nmm/page_alloc.c-1217-\nmm/page_alloc.c:1218:#ifdef CONFIG_MEM_ALLOC_PROFILING\nmm/page_alloc.c-1219-\n--\nmm/page_alloc.c=1284=static inline void pgalloc_tag_sub_pages(struct alloc_tag tag, unsigned int nr)\n--\nmm/page_alloc.c-1289-\nmm/page_alloc.c:1290:#else / CONFIG_MEM_ALLOC_PROFILING /\nmm/page_alloc.c-1291-\n--\nmm/page_alloc.c=1295=static inline void pgalloc_tag_sub_pages(struct alloc_tag tag, unsigned int nr) {}\nmm/page_alloc.c-1296-\nmm/page_alloc.c:1297:#endif /* CONFIG_MEM_ALLOC_PROFILING /\nmm/page_alloc.c-1298-\n--\nmm/page_ext.c=80=static struct page_ext_operations page_ext_ops[] __initdata = {\n--\nmm/page_ext.c-86-#endif\nmm/page_ext.c:87:#ifdef CONFIG_MEM_ALLOC_PROFILING\nmm/page_ext.c-88-\t\u0026page_alloc_tagging_ops,\n--\nmm/page_ext.c=100=static unsigned long total_usage;\nmm/page_ext.c-101-\nmm/page_ext.c:102:#ifdef CONFIG_MEM_ALLOC_PROFILING_DEBUG\nmm/page_ext.c-103-/\n--\nmm/percpu-internal.h=35=struct pcpuobj_ext {\n--\nmm/percpu-internal.h-38-#endif\nmm/percpu-internal.h:39:#ifdef CONFIG_MEM_ALLOC_PROFILING\nmm/percpu-internal.h-40-\tunion codetag_ref\ttag;\n--\nmm/percpu-internal.h-43-\nmm/percpu-internal.h:44:#if defined(CONFIG_MEMCG) \|\| defined(CONFIG_MEM_ALLOC_PROFILING)\nmm/percpu-internal.h-45-#define NEED_PCPUOBJ_EXT\n--\nmm/percpu-internal.h=90=static inline bool need_pcpuobj_ext(void)\nmm/percpu-internal.h-91-{\nmm/percpu-internal.h:92:\tif (IS_ENABLED(CONFIG_MEM_ALLOC_PROFILING))\nmm/percpu-internal.h-93-\t\treturn true;\n--\nmm/percpu.c=1688=static void pcpu_memcg_free_hook(struct pcpu_chunk chunk, int off, size_t size)\n--\nmm/percpu.c-1692-\nmm/percpu.c:1693:#ifdef CONFIG_MEM_ALLOC_PROFILING\nmm/percpu.c-1694-static void pcpu_alloc_tag_alloc_hook(struct pcpu_chunk chunk, int off,\n--\nmm/show_mem.c=408=void __show_mem(unsigned int filter, const nodemask_t nodemask,\n--\nmm/show_mem.c-434-#endif\nmm/show_mem.c:435:#ifdef CONFIG_MEM_ALLOC_PROFILING\nmm/show_mem.c-436-\tstatic DEFINE_SPINLOCK(mem_alloc_profiling_spinlock);\n--\nmm/slab.h=604=struct slabobj_ext {\n--\nmm/slab.h-612-#endif\nmm/slab.h:613:#ifdef CONFIG_MEM_ALLOC_PROFILING\nmm/slab.h-614-\t\tunion codetag_ref _ctref;\n--\nmm/slab.h-618-\nmm/slab.h:619:#ifdef CONFIG_MEM_ALLOC_PROFILING\nmm/slab.h:620:DECLARE_STATIC_KEY_MAYBE(CONFIG_MEM_ALLOC_PROFILING_ENABLED_BY_DEFAULT,\nmm/slab.h-621-\t\t\t slab_obj_ext_has_codetag_key);\n--\nmm/slab.h=623=static inline bool slab_obj_ext_has_codetag(void)\nmm/slab.h-624-{\nmm/slab.h:625:\treturn static_branch_maybe(CONFIG_MEM_ALLOC_PROFILING_ENABLED_BY_DEFAULT,\nmm/slab.h-626-\t\t\t\t \u0026slab_obj_ext_has_codetag_key);\n--\nmm/slab.h=807=slab_obj_ext_set_objcg(struct slab slab, struct slabobj_ext obj_ext,\n--\nmm/slab.h-816-\nmm/slab.h:817:#ifdef CONFIG_MEM_ALLOC_PROFILING\nmm/slab.h-818-static inline union codetag_ref \n--\nmm/slub.c=214=static DEFINE_STATIC_KEY_FALSE(strict_numa);\n--\nmm/slub.c-216-\nmm/slub.c:217:#ifdef CONFIG_MEM_ALLOC_PROFILING\nmm/slub.c:218:DEFINE_STATIC_KEY_MAYBE(CONFIG_MEM_ALLOC_PROFILING_ENABLED_BY_DEFAULT,\nmm/slub.c-219-\t\t\tslab_obj_ext_has_codetag_key);\n--\nmm/slub.c=2069=static inline void dec_slabs_node(struct kmem_cache s, int node,\n--\nmm/slub.c-2086-\nmm/slub.c:2087:#ifdef CONFIG_MEM_ALLOC_PROFILING_DEBUG\nmm/slub.c-2088-\n--\nmm/slub.c=2124=static inline void handle_failed_objexts_alloc(struct slab slab,\n--\nmm/slub.c-2149-\nmm/slub.c:2150:#else / CONFIG_MEM_ALLOC_PROFILING_DEBUG /\nmm/slub.c-2151-\n--\nmm/slub.c=2154=static inline void handle_failed_objexts_alloc(struct slab slab,\n--\nmm/slub.c-2156-\nmm/slub.c:2157:#endif /* CONFIG_MEM_ALLOC_PROFILING_DEBUG /\nmm/slub.c-2158-\n--\nmm/slub.c=2346=static inline void alloc_slab_obj_exts_early(struct kmem_cache s,\n--\nmm/slub.c-2352-\nmm/slub.c:2353:#ifdef CONFIG_MEM_ALLOC_PROFILING\nmm/slub.c-2354-\n--\nmm/slub.c=2469=static void __init slab_obj_ext_has_codetag_init(void)\n--\nmm/slub.c-2480-\nmm/slub.c:2481:#else /* CONFIG_MEM_ALLOC_PROFILING /\nmm/slub.c-2482-\n--\nmm/slub.c=2495=static inline void slab_obj_ext_has_codetag_init(void)\n--\nmm/slub.c-2498-\nmm/slub.c:2499:#endif / CONFIG_MEM_ALLOC_PROFILING */\nmm/slub.c-2500-\n" }
5/2	2026/09/23 23:22	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 15477 output: 34 thoughts: 33 Thoughts: Okay, let's dive into this. Here's how I'd approach that kernel configuration investigation, from my perspective: Investigating the Dependency Chain for `CONFIG_MEM_ALLOC_PROFILING` Right, so I need to understand what's gating `CONFIG_MEM_ALLOC_PROFILING`. My initial instinct is to check `mm/Kconfig.debug`. I know that's often where the more esoteric debugging features and related configurations reside. Line 323 feels like a reasonable starting point, given the name of the config. Let's start there and see what the dependencies are. I'll need to understand if there are any prerequisite configurations that need to be enabled for this to be set. It could be some fundamental memory management or debug option. I'll mentally parse the Kconfig syntax and map out the conditional dependencies if it's not straightforward. Maybe I'll need to recursively investigate any other configurations that that config depends on. That's the first step to truly understanding the feature.
6/2	2026/09/23 23:22	tool	read-file	0m Args: { "File": "mm/Kconfig.debug", "FirstLine": 320, "LineCount": 40 } Results: { "Contents": " 320:\t\n 321:\t\t If in doubt, say N.\n 322:\t\n 323:\tconfig MEM_ALLOC_PROFILING\n 324:\t\tbool \"Enable memory allocation profiling\"\n 325:\t\tdefault n\n 326:\t\tdepends on MMU\n 327:\t\tdepends on PROC_FS\n 328:\t\tselect CODE_TAGGING\n 329:\t\tselect PAGE_EXTENSION\n 330:\t\tselect SLAB_OBJ_EXT\n 331:\t\thelp\n 332:\t\t Track allocation source code and record total allocation size\n 333:\t\t initiated at that code location. The mechanism can be used to track\n 334:\t\t memory leaks with a low performance and memory impact.\n 335:\t\n 336:\tconfig MEM_ALLOC_PROFILING_ENABLED_BY_DEFAULT\n 337:\t\tbool \"Enable memory allocation profiling by default\"\n 338:\t\tdefault y\n 339:\t\tdepends on MEM_ALLOC_PROFILING\n 340:\t\n 341:\tconfig MEM_ALLOC_PROFILING_DEBUG\n 342:\t\tbool \"Memory allocation profiler debugging\"\n 343:\t\tdefault n\n 344:\t\tdepends on MEM_ALLOC_PROFILING\n 345:\t\tselect MEM_ALLOC_PROFILING_ENABLED_BY_DEFAULT\n 346:\t\thelp\n 347:\t\t Adds warnings with helpful error messages for memory allocation\n 348:\t\t profiling.\n" }
7/2	2026/09/23 23:22	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 16157 output: 24 thoughts: 19 Thoughts: Here's my attempt at summarizing the thought process, tailored for an expert audience: Investigating `/proc/allocinfo` Access and Creation Okay, so I need to quickly refresh my understanding of `/proc/allocinfo`. First, I'm thinking, let's dive into the kernel sources. I need to figure out exactly how this pseudo-file is constructed. Is it dynamically generated, pulled from a specific data structure, or some other mechanism? I'm hoping it's relatively straightforward, but I'll need to trace the code path. Then, the more interesting question is who has access. What are the permissions on this thing? I assume it's root-only, given the potential for leaking memory allocation information, but I should check and make no assumptions. I need to verify which user and group IDs are assigned and what, if any, capabilities are required. The security implications here are potentially significant, so I need to ensure my understanding of access control is ironclad. I'll probably start with an `ls -l` on the file and then move towards looking at the kernel code that handles the `open()` and `read()` calls, if I can find it quickly.
8/2	2026/09/23 23:23	tool	grepper	0m Args: { "Expression": "allocinfo", "PathPrefix": "mm/" } Results: { "Output": "mm/alloc_tag.c-27-\nmm/alloc_tag.c:28:#define ALLOCINFO_FILE_NAME\t\t\"allocinfo\"\nmm/alloc_tag.c-29-#define MODULE_ALLOC_TAG_VMAP_SIZE\t(100000UL * sizeof(struct alloc_tag))\n--\nmm/alloc_tag.c=75=int alloc_tag_ref_offs;\nmm/alloc_tag.c-76-\nmm/alloc_tag.c:77:struct allocinfo_private {\nmm/alloc_tag.c-78-\tstruct codetag_iterator iter;\n--\nmm/alloc_tag.c-80-\tbool print_header;\nmm/alloc_tag.c:81:\tstruct allocinfo_filter filter;\nmm/alloc_tag.c-82-\t/* ioctl uses a separate iterator not to interfere with reads /\n--\nmm/alloc_tag.c-87-\nmm/alloc_tag.c:88:static void allocinfo_start(struct seq_file m, loff_t pos)\nmm/alloc_tag.c-89-{\nmm/alloc_tag.c:90:\tstruct allocinfo_private priv;\nmm/alloc_tag.c-91-\tloff_t node = pos;\nmm/alloc_tag.c-92-\nmm/alloc_tag.c:93:\tpriv = (struct allocinfo_private )m-\u003eprivate;\nmm/alloc_tag.c-94-\tcodetag_lock_module_list(alloc_tag_cttype);\n--\nmm/alloc_tag.c-104-\nmm/alloc_tag.c:105:static void allocinfo_next(struct seq_file m, void arg, loff_t pos)\nmm/alloc_tag.c-106-{\nmm/alloc_tag.c:107:\tstruct allocinfo_private priv = (struct allocinfo_private )arg;\nmm/alloc_tag.c-108-\tstruct codetag ct;\n--\nmm/alloc_tag.c-118-\nmm/alloc_tag.c:119:static void allocinfo_stop(struct seq_file m, void arg)\nmm/alloc_tag.c-120-{\n--\nmm/alloc_tag.c-123-\nmm/alloc_tag.c:124:static void print_allocinfo_header(struct seq_buf buf)\nmm/alloc_tag.c-125-{\nmm/alloc_tag.c-126-\t/ Output format version, so we can change it. /\nmm/alloc_tag.c:127:\tseq_buf_printf(buf, \"allocinfo - version: 2.0\\n\");\nmm/alloc_tag.c-128-\tseq_buf_printf(buf, \"# \u003csize\u003e \u003ccalls\u003e \u003ctag info\u003e\\n\");\n--\nmm/alloc_tag.c=131=static void alloc_tag_to_text(struct seq_buf out, struct codetag ct)\n--\nmm/alloc_tag.c-144-\nmm/alloc_tag.c:145:static int allocinfo_show(struct seq_file m, void arg)\nmm/alloc_tag.c-146-{\nmm/alloc_tag.c:147:\tstruct allocinfo_private priv = (struct allocinfo_private )arg;\nmm/alloc_tag.c-148-\tchar bufp;\n--\nmm/alloc_tag.c-153-\tif (priv-\u003eprint_header) {\nmm/alloc_tag.c:154:\t\tprint_allocinfo_header(\u0026buf);\nmm/alloc_tag.c-155-\t\tpriv-\u003eprint_header = false;\n--\nmm/alloc_tag.c-161-\nmm/alloc_tag.c:162:static const struct seq_operations allocinfo_seq_op = {\nmm/alloc_tag.c:163:\t.start\t= allocinfo_start,\nmm/alloc_tag.c:164:\t.next\t= allocinfo_next,\nmm/alloc_tag.c:165:\t.stop\t= allocinfo_stop,\nmm/alloc_tag.c:166:\t.show\t= allocinfo_show,\nmm/alloc_tag.c-167-};\n--\nmm/alloc_tag.c-170- * Initializes seq_file operations and allocates private state when opening\nmm/alloc_tag.c:171: * the /proc/allocinfo procfs entry.\nmm/alloc_tag.c-172- /\nmm/alloc_tag.c:173:static int allocinfo_open(struct inode inode, struct file file)\nmm/alloc_tag.c-174-{\n--\nmm/alloc_tag.c-176-\nmm/alloc_tag.c:177:\tret = seq_open_private(file, \u0026allocinfo_seq_op,\nmm/alloc_tag.c:178:\t\t\t sizeof(struct allocinfo_private));\nmm/alloc_tag.c-179-\tif (!ret) {\nmm/alloc_tag.c-180-\t\tstruct seq_file m = file-\u003eprivate_data;\nmm/alloc_tag.c:181:\t\tstruct allocinfo_private priv = m-\u003eprivate;\nmm/alloc_tag.c-182-\n--\nmm/alloc_tag.c-189- Cleans up the seq_file state and frees up the private state allocated in\nmm/alloc_tag.c:190: * allocinfo_open() when closing the /proc/allocinfo file descriptor.\nmm/alloc_tag.c-191- /\nmm/alloc_tag.c:192:static int allocinfo_release(struct inode inode, struct file file)\nmm/alloc_tag.c-193-{\nmm/alloc_tag.c-194-\tstruct seq_file m = file-\u003eprivate_data;\nmm/alloc_tag.c:195:\tstruct allocinfo_private priv = m-\u003eprivate;\nmm/alloc_tag.c-196-\n--\nmm/alloc_tag.c-207- /\nmm/alloc_tag.c:208:static const char allocinfo_str(const char str)\nmm/alloc_tag.c-209-{\n--\nmm/alloc_tag.c-218-/* Copy a string and trim from the beginning if it's too long /\nmm/alloc_tag.c:219:static void allocinfo_copy_str(char dest, const char src)\nmm/alloc_tag.c-220-{\nmm/alloc_tag.c:221:\tstrscpy_pad(dest, allocinfo_str(src), ALLOCINFO_STR_SIZE);\nmm/alloc_tag.c-222-}\n--\nmm/alloc_tag.c-224-/ Compare two strings and only consider the trimmed suffix if s1 is too long /\nmm/alloc_tag.c:225:static int allocinfo_cmp_str(const char str, const char template)\nmm/alloc_tag.c-226-{\nmm/alloc_tag.c:227:\treturn strncmp(allocinfo_str(str), template, ALLOCINFO_STR_SIZE);\nmm/alloc_tag.c-228-}\n--\nmm/alloc_tag.c-230-/ Fetch the per-CPU counters /\nmm/alloc_tag.c:231:static inline struct alloc_tag_counters allocinfo_prefetch_counters(struct codetag ct)\nmm/alloc_tag.c-232-{\n--\nmm/alloc_tag.c-236-/\nmm/alloc_tag.c:237: Populates the UAPI allocinfo_tag_data structure with active runtime\nmm/alloc_tag.c-238- * profiling counters extracted from the given kernel codetag.\nmm/alloc_tag.c-239- /\nmm/alloc_tag.c:240:static void allocinfo_to_params(struct codetag ct,\nmm/alloc_tag.c:241:\t\t\t\tstruct allocinfo_tag_data data,\nmm/alloc_tag.c-242-\t\t\t\tstruct alloc_tag_counters counters)\n--\nmm/alloc_tag.c-244-\tif (ct-\u003emodname)\nmm/alloc_tag.c:245:\t\tallocinfo_copy_str(data-\u003etag.modname, ct-\u003emodname);\nmm/alloc_tag.c-246-\telse\nmm/alloc_tag.c-247-\t\tdata-\u003etag.modname[0] = '\\0';\nmm/alloc_tag.c:248:\tallocinfo_copy_str(data-\u003etag.function, ct-\u003efunction);\nmm/alloc_tag.c:249:\tallocinfo_copy_str(data-\u003etag.filename, ct-\u003efilename);\nmm/alloc_tag.c-250-\tdata-\u003etag.lineno = ct-\u003elineno;\n--\nmm/alloc_tag.c-260- /\nmm/alloc_tag.c:261:static int allocinfo_ioctl_get_content_id(struct seq_file m, void __user arg)\nmm/alloc_tag.c-262-{\nmm/alloc_tag.c:263:\tstruct allocinfo_content_id params;\nmm/alloc_tag.c-264-\n--\nmm/alloc_tag.c-277- /\nmm/alloc_tag.c:278:static bool matches_filter(struct codetag ct, struct allocinfo_filter filter,\nmm/alloc_tag.c-279-\t\t\t struct alloc_tag_counters counters,\n--\nmm/alloc_tag.c-292-\t\t\t\treturn false;\nmm/alloc_tag.c:293:\t\t} else if (allocinfo_cmp_str(ct-\u003emodname, filter-\u003efields.modname))\nmm/alloc_tag.c-294-\t\t\treturn false;\n--\nmm/alloc_tag.c-297-\tif ((filter-\u003emask \u0026 ALLOCINFO_FILTER_MASK_FUNCTION) \u0026\u0026\nmm/alloc_tag.c:298:\t ct-\u003efunction \u0026\u0026 allocinfo_cmp_str(ct-\u003efunction, filter-\u003efields.function))\nmm/alloc_tag.c-299-\t\treturn false;\n--\nmm/alloc_tag.c-301-\tif ((filter-\u003emask \u0026 ALLOCINFO_FILTER_MASK_FILENAME) \u0026\u0026\nmm/alloc_tag.c:302:\t ct-\u003efilename \u0026\u0026 allocinfo_cmp_str(ct-\u003efilename, filter-\u003efields.filename))\nmm/alloc_tag.c-303-\t\treturn false;\n--\nmm/alloc_tag.c-316-\t\tif (!fetched_counters) {\nmm/alloc_tag.c:317:\t\t\tcounters = allocinfo_prefetch_counters(ct);\nmm/alloc_tag.c-318-\t\t\tfetched_counters = true;\n--\nmm/alloc_tag.c-341- /\nmm/alloc_tag.c:342:static int allocinfo_ioctl_get_at(struct seq_file m, void __user arg)\nmm/alloc_tag.c-343-{\nmm/alloc_tag.c:344:\tstruct allocinfo_private priv;\nmm/alloc_tag.c-345-\tstruct codetag ct;\nmm/alloc_tag.c:346:\tstruct allocinfo_get_at params = {0};\nmm/alloc_tag.c-347-\t__u64 skip_count;\n--\nmm/alloc_tag.c-395-\t\tif (!fetched_counters)\nmm/alloc_tag.c:396:\t\t\tcounters = allocinfo_prefetch_counters(ct);\nmm/alloc_tag.c:397:\t\tallocinfo_to_params(ct, \u0026params.data, \u0026counters);\nmm/alloc_tag.c-398-\t\tpriv-\u003epositioned = true;\n--\nmm/alloc_tag.c-416- /\nmm/alloc_tag.c:417:static int allocinfo_ioctl_get_next(struct seq_file m, void __user arg)\nmm/alloc_tag.c-418-{\nmm/alloc_tag.c:419:\tstruct allocinfo_private priv;\nmm/alloc_tag.c-420-\tstruct codetag ct;\nmm/alloc_tag.c:421:\tstruct allocinfo_tag_data params;\nmm/alloc_tag.c-422-\tint ret = 0;\n--\nmm/alloc_tag.c-446-\t\tif (!fetched_counters)\nmm/alloc_tag.c:447:\t\t\tcounters = allocinfo_prefetch_counters(ct);\nmm/alloc_tag.c:448:\t\tallocinfo_to_params(ct, \u0026params, \u0026counters);\nmm/alloc_tag.c-449-\t}\n--\nmm/alloc_tag.c=464=static bool alloc_tag_trace_toggle(struct alloc_tag tag, bool enable)\n--\nmm/alloc_tag.c-487- /\nmm/alloc_tag.c:488:static int allocinfo_ioctl_toggle_trace(struct seq_file m, void __user arg)\nmm/alloc_tag.c-489-{\nmm/alloc_tag.c:490:\tstruct allocinfo_toggle_traces params;\nmm/alloc_tag.c-491-\tstruct codetag_iterator iter;\n--\nmm/alloc_tag.c-502-\nmm/alloc_tag.c:503:\tstruct allocinfo_filter filter = {\nmm/alloc_tag.c-504-\t\t.mask = ALLOCINFO_FILTER_MASK_MODNAME \|\n--\nmm/alloc_tag.c-539-/\nmm/alloc_tag.c:540: Entry point ioctl function for /proc/allocinfo routing requests to fetch the\nmm/alloc_tag.c-541- * layout content ID, seek to a specific tag, or read sequential tags.\nmm/alloc_tag.c-542- /\nmm/alloc_tag.c:543:static long allocinfo_ioctl(struct file file, unsigned int cmd,\nmm/alloc_tag.c-544-\t\t\t unsigned long __arg)\n--\nmm/alloc_tag.c-550-\tcase ALLOCINFO_IOC_CONTENT_ID:\nmm/alloc_tag.c:551:\t\tret = allocinfo_ioctl_get_content_id(file-\u003eprivate_data, arg);\nmm/alloc_tag.c-552-\t\tbreak;\nmm/alloc_tag.c-553-\tcase ALLOCINFO_IOC_GET_AT:\nmm/alloc_tag.c:554:\t\tret = allocinfo_ioctl_get_at(file-\u003eprivate_data, arg);\nmm/alloc_tag.c-555-\t\tbreak;\nmm/alloc_tag.c-556-\tcase ALLOCINFO_IOC_GET_NEXT:\nmm/alloc_tag.c:557:\t\tret = allocinfo_ioctl_get_next(file-\u003eprivate_data, arg);\nmm/alloc_tag.c-558-\t\tbreak;\nmm/alloc_tag.c-559-\tcase ALLOCINFO_IOC_TOGGLE_TRACE:\nmm/alloc_tag.c:560:\t\tret = allocinfo_ioctl_toggle_trace(file-\u003eprivate_data, arg);\nmm/alloc_tag.c-561-\t\tbreak;\n--\nmm/alloc_tag.c-570-#ifdef CONFIG_COMPAT\nmm/alloc_tag.c:571:static long allocinfo_compat_ioctl(struct file file, unsigned int cmd,\nmm/alloc_tag.c-572-\t\t\t\t unsigned long arg)\nmm/alloc_tag.c-573-{\nmm/alloc_tag.c:574:\treturn allocinfo_ioctl(file, cmd, (unsigned long)compat_ptr(arg));\nmm/alloc_tag.c-575-}\n--\nmm/alloc_tag.c-577-\nmm/alloc_tag.c:578:static const struct proc_ops allocinfo_proc_ops = {\nmm/alloc_tag.c:579:\t.proc_open\t\t= allocinfo_open,\nmm/alloc_tag.c-580-\t.proc_read_iter\t\t= seq_read_iter,\nmm/alloc_tag.c-581-\t.proc_lseek\t\t= seq_lseek,\nmm/alloc_tag.c:582:\t.proc_release\t\t= allocinfo_release,\nmm/alloc_tag.c:583:\t.proc_ioctl\t\t= allocinfo_ioctl,\nmm/alloc_tag.c-584-#ifdef CONFIG_COMPAT\nmm/alloc_tag.c:585:\t.proc_compat_ioctl\t= allocinfo_compat_ioctl,\nmm/alloc_tag.c-586-#endif\n--\nmm/alloc_tag.c=676=void pgalloc_tag_swap(struct folio new, struct folio old)\n--\nmm/alloc_tag.c-715-\nmm/alloc_tag.c:716:static void remove_allocinfo_file(struct work_struct work)\nmm/alloc_tag.c-717-{\n--\nmm/alloc_tag.c-720-\nmm/alloc_tag.c:721:static DECLARE_WORK(remove_allocinfo_work, remove_allocinfo_file);\nmm/alloc_tag.c-722-\nmm/alloc_tag.c=723=static void shutdown_mem_profiling(bool remove_file)\n--\nmm/alloc_tag.c-731-\tif (remove_file)\nmm/alloc_tag.c:732:\t\tschedule_work(\u0026remove_allocinfo_work);\nmm/alloc_tag.c-733-\tmem_profiling_support = false;\n--\nmm/alloc_tag.c=736=void __init alloc_tag_sec_init(void)\n--\nmm/alloc_tag.c-753-\tif (kernel_tags.count \u003e (1UL \u003c\u003c NR_UNUSED_PAGEFLAG_BITS)) {\nmm/alloc_tag.c:754:\t\tshutdown_mem_profiling(false); /* allocinfo file does not exist yet */\nmm/alloc_tag.c-755-\t\tpr_err(\"%lu allocation tags cannot be references using %d available page flag bits. Memory allocation profiling is disabled!\\n\",\n--\nmm/alloc_tag.c=1473=static int __init alloc_tag_init(void)\n--\nmm/alloc_tag.c-1495-\nmm/alloc_tag.c:1496:\tif (!proc_create(ALLOCINFO_FILE_NAME, 0400, NULL, \u0026allocinfo_proc_ops)) {\nmm/alloc_tag.c-1497-\t\tpr_err(\"Failed to create %s file\\n\", ALLOCINFO_FILE_NAME);\n--\nmm/vmalloc.c=5433=static int __init proc_vmalloc_init(void)\nmm/vmalloc.c-5434-{\nmm/vmalloc.c:5435:\tproc_create_single(\"vmallocinfo\", 0400, NULL, vmalloc_info_show);\nmm/vmalloc.c-5436-\treturn 0;\n" }
9/2	2026/09/23 23:23	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 21326 output: 27 thoughts: 2859 Thoughts: Analysis of the Patch: WorthFuzzing Determination Okay, let's break this down systematically. I'm looking at this patch and my initial thought is, based on the `proc_create` call and the `ioctl` implementation, it seems like there's a new `/proc/allocinfo` interface and associated functionality for manipulating allocation tracing. The presence of `syzkaller` and root privileges are relevant here, meaning this could be targeted. Initially, I see the term "tracepoints" and think, "Is this just logging?" Let me check the negative criteria: "Purely decorative logging" is an immediate filter, but does this just add logging? No. This patch is far more involved. I can see that the `struct codetag` is being modified, changing the `flags` field to an `atomic_t`, along with a change in the related functions, `alloc_tag_set_inaccurate` and `alloc_tag_is_inaccurate`. This goes beyond simple logging and impacts core data structures within the kernel's memory management. It's not just decorative, this is fundamental change to the type and associated functions, modifying the data structure. The addition of the new `ioctl` command, `ALLOCINFO_IOC_TOGGLE_TRACE`, is a significant red flag. This enables fine-grained control over tracing. Further, there is also the `alloc_tag_trace_toggle` which is added. This function modifies the global `alloc_tag_trace_cnt` atomic variable and interacts with `static_branch_enable` and `static_branch_disable`. This means patching of the code which modifies execution paths. This is a crucial alteration! The analysis of `unload_module` is interesting. It indicates a concurrency problem, with `alloc_tag_trace_toggle` not holding `alloc_tag_trace_mutex` when modules are unloaded. This could lead to data races on `alloc_tag_trace_cnt` and incorrect static branch state. The critical section's locking looks... problematic. This patch also adds a new `ALLOCINFO_FILTER_MASK_TRACE_ON` filter, further increasing its attack surface. This is integrated into functions like `matches_filter`, which are used when iterating over all of the codetags, so it is used in several places. I can confirm that `/proc/allocinfo` is created and available in standard virtualized environments, assuming `CONFIG_MEM_ALLOC_PROFILING` is enabled. In conclusion, this patch is a clear modification of the kernel's control flow, and data structures. It adds an `ioctl`, introduces new locking considerations, and affects key memory management code. This patch definitely should be considered worthy of fuzzing. It introduces concurrency issues, it adds a new attack surface, and it touches core kernel components.
10/2	2026/09/23 23:23	tool	grepper	0m Args: { "Expression": "alloc_tag_init", "PathPrefix": "mm/" } Results: { "Output": "mm/alloc_tag.c=1470=static inline void sysctl_init(void) {}\n--\nmm/alloc_tag.c-1472-\nmm/alloc_tag.c:1473:static int __init alloc_tag_init(void)\nmm/alloc_tag.c-1474-{\n--\nmm/alloc_tag.c-1518-}\nmm/alloc_tag.c:1519:module_init(alloc_tag_init);\n" }
11/2	2026/09/23 23:23	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 24951 output: 36 thoughts: 31 Thoughts: Okay, let's dive into this. Here's my thought process on the matter: Analyzing the Dependency of /proc/allocinfo Right, the goal is to understand what triggers the `/proc/allocinfo` file's presence and functionality. To get a clear picture of its behavior, I need to see how the kernel sets it up. The logical entry point to investigate is `alloc_tag_init`. By examining that function, I can pinpoint the crucial conditions, flags, and data structures involved in making `/proc/allocinfo` available. Understanding these details is key to diagnosing any problems or predicting the behavior of the allocator information. I'll focus on the pre-conditions and any relevant initializations related to enabling this procfs entry.
12/2	2026/09/23 23:23	tool	read-file	0m Args: { "File": "mm/alloc_tag.c", "FirstLine": 1473, "LineCount": 45 } Results: { "Contents": "1473:\tstatic int __init alloc_tag_init(void)\n1474:\t{\n1475:\t\tconst struct codetag_type_desc desc = {\n1476:\t\t\t.section\t\t= ALLOC_TAG_SECTION_NAME,\n1477:\t\t\t.tag_size\t\t= sizeof(struct alloc_tag),\n1478:\t#ifdef CONFIG_MODULES\n1479:\t\t\t.needs_section_mem\t= needs_section_mem,\n1480:\t\t\t.alloc_section_mem\t= reserve_module_tags,\n1481:\t\t\t.free_section_mem\t= release_module_tags,\n1482:\t\t\t.module_load\t\t= load_module,\n1483:\t\t\t.module_unload\t\t= unload_module,\n1484:\t\t\t.module_replaced\t= replace_module,\n1485:\t#endif\n1486:\t\t};\n1487:\t\tint res;\n1488:\t\n1489:\t\tsysctl_init();\n1490:\t\n1491:\t\tif (!mem_profiling_support) {\n1492:\t\t\tpr_info(\"Memory allocation profiling is not supported!\\n\");\n1493:\t\t\treturn 0;\n1494:\t\t}\n1495:\t\n1496:\t\tif (!proc_create(ALLOCINFO_FILE_NAME, 0400, NULL, \u0026allocinfo_proc_ops)) {\n1497:\t\t\tpr_err(\"Failed to create %s file\\n\", ALLOCINFO_FILE_NAME);\n1498:\t\t\tshutdown_mem_profiling(false);\n1499:\t\t\treturn -ENOMEM;\n1500:\t\t}\n1501:\t\n1502:\t\tres = alloc_mod_tags_mem();\n1503:\t\tif (res) {\n1504:\t\t\tpr_err(\"Failed to reserve address space for module tags, errno = %d\\n\", res);\n1505:\t\t\tshutdown_mem_profiling(true);\n1506:\t\t\treturn res;\n1507:\t\t}\n1508:\t\n1509:\t\talloc_tag_cttype = codetag_register_type(\u0026desc);\n1510:\t\tif (IS_ERR(alloc_tag_cttype)) {\n1511:\t\t\tpr_err(\"Allocation tags registration failed, errno = %pe\\n\", alloc_tag_cttype);\n1512:\t\t\tfree_mod_tags_mem();\n1513:\t\t\tshutdown_mem_profiling(true);\n1514:\t\t\treturn PTR_ERR(alloc_tag_cttype);\n1515:\t\t}\n1516:\t\n1517:\t\treturn 0;\n" }
13/2	2026/09/23 23:23	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 25875 output: 34 thoughts: 97 Thoughts: Okay, let's dive into this. Here's what I'm thinking, as I'm looking at this code: Checking Memory Profiling Support Alright, first thing's first, I need to understand how the memory profiling support is set up. Let's see... looking at lines 33-35, it's pretty straightforward, it seems to be controlled by the `CONFIG_MEM_ALLOC_PROFILING_ENABLED_BY_DEFAULT` define. If that's enabled at compile time, `mem_profiling_support` is initialized to `true`; otherwise, it's `false`. Standard conditional compilation, nothing too fancy. I need to keep in mind, I need to check the configuration to see which is active, if there are any issues reported, or if I need to run a test to determine the default value. Now, I think I need to look at the implementation, at lines 30-50 of `mm/alloc_tag.c`. That should give me the real meat of how this `mem_profiling_support` boolean is used. I'm expecting to see calls to enable or disable it, perhaps some conditionals that check its state before doing allocation profiling. I should get a better picture of the entire function from here. I need to understand where this is used within the memory management code.
14/2	2026/09/23 23:23	tool	read-file	0m Args: { "File": "mm/alloc_tag.c", "FirstLine": 30, "LineCount": 30 } Results: { "Contents": " 30:\t#define SECTION_START(NAME)\t\t(CODETAG_SECTION_START_PREFIX NAME)\n 31:\t#define SECTION_STOP(NAME)\t\t(CODETAG_SECTION_STOP_PREFIX NAME)\n 32:\t\n 33:\t#ifdef CONFIG_MEM_ALLOC_PROFILING_ENABLED_BY_DEFAULT\n 34:\tstatic bool mem_profiling_support = true;\n 35:\t#else\n 36:\tstatic bool mem_profiling_support;\n 37:\t#endif\n 38:\t\n 39:\t/\n 40:\t Memory allocation profiling is permanently disabled and cannot be enabled.\n 41:\t * Must be called after setup_early_mem_profiling().\n 42:\t /\n 43:\tbool mem_alloc_profiling_permanently_disabled(void)\n 44:\t{\n 45:\t\treturn !mem_profiling_support;\n 46:\t}\n 47:\t\n 48:\tstatic struct codetag_type alloc_tag_cttype;\n 49:\t\n 50:\t#ifdef CONFIG_ARCH_MODULE_NEEDS_WEAK_PER_CPU\n 51:\tDEFINE_PER_CPU(struct alloc_tag_counters, _shared_alloc_tag);\n 52:\tEXPORT_SYMBOL(_shared_alloc_tag);\n 53:\t#endif\n 54:\t\n 55:\tDEFINE_STATIC_KEY_MAYBE(CONFIG_MEM_ALLOC_PROFILING_ENABLED_BY_DEFAULT,\n 56:\t\t\t\tmem_alloc_profiling_key);\n 57:\tEXPORT_SYMBOL(mem_alloc_profiling_key);\n 58:\t\n 59:\tDEFINE_STATIC_KEY_FALSE(mem_profiling_compressed);\n" }
15/2	2026/09/23 23:23	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 26750 output: 27 thoughts: 241 Thoughts: My Analysis of Memory Allocation Profiling Configuration Okay, so I see the logic here: if both `CONFIG_MEM_ALLOC_PROFILING` is set to 'y' and `CONFIG_MEM_ALLOC_PROFILING_ENABLED_BY_DEFAULT` is also set to 'y', then the feature will be both supported and enabled. That much is straightforward. Now, I need to get a handle on the necessary configuration options. First, I'll drill down into `CONFIG_MEM_ALLOC_PROFILING` and its dependencies. Let's see... looking at `mm/Kconfig.debug`, it's a boolean option, disabled by default. It depends on `MMU` (understandable), `PROC_FS` (okay, that makes sense for reporting), it also selects `CODE_TAGGING`, `PAGE_EXTENSION`, and `SLAB_OBJ_EXT`. Right, those selections are crucial – they enable the underlying mechanisms for the profiling to work. Good. I'm noting that `CONFIG_MEM_ALLOC_PROFILING_ENABLED_BY_DEFAULT` defaults to 'y' if `CONFIG_MEM_ALLOC_PROFILING` itself is enabled. Now, a key question: Does this whole system require `TRACING`? I need to check if any of the associated trace events have prerequisites, or if they're dependent on `TRACEPOINTS` or `EVENT_TRACING` being configured. I'll search for where the tracepoints for this are defined, starting with `trace/events/alloc_tag.h`. That should give me a good indication of whether there are any tracing requirements.
16/2	2026/09/23 23:23	tool	grepper	0m Args: { "Expression": "alloc_tag\\.h", "PathPrefix": "mm/" } Results: { "Output": "mm/alloc_tag.c-1-// SPDX-License-Identifier: GPL-2.0-only\nmm/alloc_tag.c:2:#include \u003clinux/alloc_tag.h\u003e\nmm/alloc_tag.c-3-#include \u003clinux/execmem.h\u003e\n--\nmm/alloc_tag.c-10-#include \u003clinux/page_ext.h\u003e\nmm/alloc_tag.c:11:#include \u003clinux/pgalloc_tag.h\u003e\nmm/alloc_tag.c-12-#include \u003clinux/proc_fs.h\u003e\n--\nmm/alloc_tag.c-19-#include \u003clinux/kmemleak.h\u003e\nmm/alloc_tag.c:20:#include \u003cuapi/linux/alloc_tag.h\u003e\nmm/alloc_tag.c-21-\nmm/alloc_tag.c-22-#define CREATE_TRACE_POINTS\nmm/alloc_tag.c:23:#include \u003ctrace/events/alloc_tag.h\u003e\nmm/alloc_tag.c-24-\n--\nmm/huge_memory.c-41-#include \u003clinux/pgalloc.h\u003e\nmm/huge_memory.c:42:#include \u003clinux/pgalloc_tag.h\u003e\nmm/huge_memory.c-43-#include \u003clinux/pagewalk.h\u003e\n--\nmm/page_alloc.c-56-#include \u003clinux/cacheinfo.h\u003e\nmm/page_alloc.c:57:#include \u003clinux/pgalloc_tag.h\u003e\nmm/page_alloc.c-58-#include \u003casm/div64.h\u003e\n--\nmm/page_ext.c-12-#include \u003clinux/rcupdate.h\u003e\nmm/page_ext.c:13:#include \u003clinux/pgalloc_tag.h\u003e\nmm/page_ext.c-14-#include \u003clinux/iommu-debug-pagealloc.h\u003e\n" }
17/2	2026/09/23 23:23	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 27847 output: 30 thoughts: 1682 Thoughts: Tracing Memory Allocations and Unloading Modules: A Deep Dive Okay, so I need to understand how tracing works within the Linux kernel, specifically concerning memory allocations and module unloading. My initial thought is to check how `TRACE_EVENT` behaves with and without tracing enabled (CONFIG_EVENT_TRACING / TRACING). I know that `<trace/events/...>` with `TRACE_EVENT` often defines empty stubs when tracing is off, but to actually use and test the tracepoint events, `CONFIG_TRACING` or `CONFIG_EVENT_TRACING` is usually needed. Let's dive into the `mm/alloc_tag.c` file. I see functions like `__alloc_tag_trace_hit`, `alloc_tag_trace_mem_alloc`, and `alloc_tag_trace_mem_free`, all using `trace_alloc_tag_hit`, etc. These are all `EXPORT_SYMBOL` which is important. Now, how are these functions actually called? I need to check the callsites. Aha! `alloc_tag_trace_hit` is an inline function that uses `alloc_tag_trace_enabled`. Then, in `alloc_hooks_tag`, I see `alloc_tag_trace_hit(_tag)` being called if `mem_alloc_profiling_enabled()` is true. This looks like it captures the caller's stack trace. Further, `alloc_tag_add` uses `alloc_tag_trace_mem_alloc` for successful allocations and `alloc_tag_sub` uses `alloc_tag_trace_mem_free` for frees. Okay, so `alloc_hooks_tag`, `alloc_tag_add`, and `alloc_tag_sub` seem to be called during memory allocations and frees. And they are all called across the entire kernel when `MEM_ALLOC_PROFILING` is enabled. Time to look at `alloc_tag_trace_enabled`. This uses a `static_branch_unlikely(&alloc_tag_trace_key)`. So, the tracing is enabled when an ioctl enables tracing for a tag through `ALLOCINFO_IOC_TOGGLE_TRACE`. That ioctl calls `alloc_tag_trace_toggle` and enables `static_branch_enable(&alloc_tag_trace_key)`! So when an ioctl enables tracing for a particular tag, or all allocations for all tags, we are good to go! When tracing is enabled, `alloc_tag_trace_enabled` checks `alloc_tag_trace_key` and if `alloc_tag_is_traced(tag)` returns true. Then `__alloc_tag_trace_hit(tag)` is called, and `alloc_tag_trace_mem_alloc` and `alloc_tag_trace_mem_free` are called. Got it. But now, what happens when a module is unloaded? I need to look at `unload_module`. In `unload_module`, `alloc_tag_trace_toggle` is called for the tags within the module being unloaded. This looks like a cleanup step. But here's the critical question: what if there's an active allocation from a module being unloaded, or a race condition with `allocinfo_ioctl_toggle_trace`? This could be bad. Okay, let's look into `allocinfo_ioctl_toggle_trace`. Here, `alloc_tag_trace_toggle` is called under `mutex_lock(&alloc_tag_trace_mutex)`. Wait, but in `unload_module`, the code doesn't take `alloc_tag_trace_mutex`! The comment claims this is protected by `down_write(&cttype->mod_lock)`. Is `allocinfo_ioctl_toggle_trace` calling `down_write` or `down_read`? I need to verify that `codetag_lock_module_list` and unlock work correctly.
18/2	2026/09/23 23:23	tool	grepper	0m Args: { "Expression": "codetag_lock_module_list", "PathPrefix": "lib/" } Results: { "Output": "lib/codetag.c=38=static LIST_HEAD(codetag_types);\nlib/codetag.c-39-\nlib/codetag.c:40:void codetag_lock_module_list(struct codetag_type *cttype)\nlib/codetag.c-41-{\n" }
19/2	2026/09/23 23:23	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 30498 output: 33 thoughts: 18 Thoughts: Okay, let's dive into this. Here's my thought process on the matter: Analyzing `lib/codetag.c` Around Line 40 Alright, I'm thinking we need to take a look at the `lib/codetag.c` file, specifically around line 40. I want to see what's happening at that point in the code. Given my expertise in this area, I'm already anticipating what might be there. I'm probably looking for a function definition, a conditional statement, or perhaps a data structure declaration that's relevant to a specific functionality or bug report I'm currently dealing with. Line 40 is a key place to get a snapshot of how things work around there. I will look for any clues. Let me start there and see what is presented.
20/2	2026/09/23 23:23	tool	read-file	0m Args: { "File": "lib/codetag.c", "FirstLine": 38, "LineCount": 40 } Results: { "Contents": " 38:\tstatic LIST_HEAD(codetag_types);\n 39:\t\n 40:\tvoid codetag_lock_module_list(struct codetag_type cttype)\n 41:\t{\n 42:\t\tdown_read(\u0026cttype-\u003emod_lock);\n 43:\t}\n 44:\t\n 45:\tbool codetag_trylock_module_list(struct codetag_type cttype)\n 46:\t{\n 47:\t\treturn down_read_trylock(\u0026cttype-\u003emod_lock) != 0;\n 48:\t}\n 49:\t\n 50:\tvoid codetag_unlock_module_list(struct codetag_type cttype)\n 51:\t{\n 52:\t\tup_read(\u0026cttype-\u003emod_lock);\n 53:\t}\n 54:\t\n 55:\tunsigned long codetag_get_content_id(struct codetag_type cttype)\n 56:\t{\n 57:\t\tlockdep_assert_held(\u0026cttype-\u003emod_lock);\n 58:\t\n 59:\t\treturn cttype-\u003econtent_id;\n 60:\t}\n 61:\t\n 62:\tunsigned int codetag_get_count(struct codetag_type cttype)\n 63:\t{\n 64:\t\tlockdep_assert_held(\u0026cttype-\u003emod_lock);\n 65:\t\n 66:\t\treturn cttype-\u003ecount;\n 67:\t}\n 68:\t\n 69:\tstruct codetag_iterator codetag_get_ct_iter(struct codetag_type cttype)\n 70:\t{\n 71:\t\tstruct codetag_iterator iter = {\n 72:\t\t\t.cttype = cttype,\n 73:\t\t\t.cmod = NULL,\n 74:\t\t\t.mod_id = 0,\n 75:\t\t\t.ct = NULL,\n 76:\t\t\t.mod_seq = 0,\n 77:\t\t};\n" }
21/2	2026/09/23 23:23	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 31246 output: 28 thoughts: 1810 Thoughts: Analysis of the Alloc Tag Tracing Patch: Worthy of Fuzzing Okay, here's the breakdown of my thought process regarding this patch series. First, I see that the `codetag_lock_module_list` function uses `down_read` and `unload_module` uses `down_write` on `cttype->mod_lock`. This means that `unload_module` and `allocinfo_ioctl_toggle_trace` can't run concurrently because the read and write locks are exclusive. However, if two `allocinfo_ioctl_toggle_trace` calls run at the same time, they both take a read lock, which is fine, but then each locks `alloc_tag_trace_mutex` inside the loop for each toggle. Okay, that could get interesting. I'm thinking, what happens if allocations happen while these toggles are going on? I remember static keys involve code modification and that can introduce all sorts of concurrency problems. User-triggered memory allocations while tracing is enabled are also a concern because they lead to calls into `trace_alloc_tag_hit`, `trace_alloc_tag_mem_alloced`, and `trace_alloc_tag_mem_freed`. So, what about `trace_alloc_tag_hit`? Ah, it calls `TRACE_EVENT` with several string fields: `modname`, `filename`, and `function`. Now, the key lies in `alloc_hooks_tag`: it calls `alloc_tag_trace_hit` during an allocation, and this is where potential issues could creep in if the `_tag` is NULL. I see that `alloc_tag_trace_hit` checks if tracing is enabled, and if so, it calls a deeper level function if the tag is not NULL. Then I realized, the tracepoint assigns strings from fields potentially in the `tag` and these fields can be null. If this check is bypassed and those strings are dereferenced, that's a potential crash. Looking at `matches_filter`, which is used in tracing, it checks `ct->function` and `ct->filename`. If those are `NULL`, then a crash is possible when `__assign_str` is called in the `tracepoint`. Also, the user can control any `tag` through `params.fields` sent by the ioctl, and this means a user can potentially control the values of `modname`, `filename`, `function`. Now, to determine if this is worth fuzzing, I'm going through the fuzzing rules. I see that the patch modifies core memory management code (`mm/alloc_tag.c`, `include/linux/alloc_tag.h`, `include/linux/codetag.h`, and `include/uapi/linux/alloc_tag.h`). It adds a new ioctl command that is user accessible, introduces locking, updates atomic codetag flags, adds tracepoints and hooks into memory allocation fast paths (`alloc_hooks_tag`, `alloc_tag_add`, `alloc_tag_sub`), and includes module unload handling. This involves memory management that's reachable from userspace, so it's a "yes" for worth fuzzing. The fact that the hooks are called on memory allocations when tracing is enabled is a red flag, too. Therefore, `WorthFuzzing` is definitely `TRUE`. Now, let's think about the enabling configs. We need `MEM_ALLOC_PROFILING` and based on `mm/Kconfig.debug`, it depends on `MMU`, `PROC_FS`, `CODE_TAGGING` and `PAGE_EXTENSION`. I also need to make sure that the system is properly initialized with either `MEM_ALLOC_PROFILING_ENABLED_BY_DEFAULT` or that the feature is enabled via command-line or sysctl. Otherwise, tracing won't be set up and the `/proc/allocinfo` entry won't exist.
22/2	2026/09/23 23:24	tool	grepper	0m Args: { "Expression": "mem_profiling_support", "PathPrefix": "mm/" } Results: { "Output": "mm/alloc_tag.c-33-#ifdef CONFIG_MEM_ALLOC_PROFILING_ENABLED_BY_DEFAULT\nmm/alloc_tag.c:34:static bool mem_profiling_support = true;\nmm/alloc_tag.c-35-#else\nmm/alloc_tag.c:36:static bool mem_profiling_support;\nmm/alloc_tag.c-37-#endif\n--\nmm/alloc_tag.c=43=bool mem_alloc_profiling_permanently_disabled(void)\nmm/alloc_tag.c-44-{\nmm/alloc_tag.c:45:\treturn !mem_profiling_support;\nmm/alloc_tag.c-46-}\n--\nmm/alloc_tag.c=723=static void shutdown_mem_profiling(bool remove_file)\n--\nmm/alloc_tag.c-727-\nmm/alloc_tag.c:728:\tif (!mem_profiling_support)\nmm/alloc_tag.c-729-\t\treturn;\n--\nmm/alloc_tag.c-732-\t\tschedule_work(\u0026remove_allocinfo_work);\nmm/alloc_tag.c:733:\tmem_profiling_support = false;\nmm/alloc_tag.c-734-}\n--\nmm/alloc_tag.c=736=void __init alloc_tag_sec_init(void)\n--\nmm/alloc_tag.c-739-\nmm/alloc_tag.c:740:\tif (!mem_profiling_support)\nmm/alloc_tag.c-741-\t\treturn;\n--\nmm/alloc_tag.c=823=static bool needs_section_mem(struct module mod, unsigned long size)\nmm/alloc_tag.c-824-{\nmm/alloc_tag.c:825:\tif (!mem_profiling_support)\nmm/alloc_tag.c-826-\t\treturn false;\n--\nmm/alloc_tag.c=1100=static int load_module(struct module mod, struct codetag start, struct codetag stop)\n--\nmm/alloc_tag.c-1107-\t/* Profiling disabled: load the module without its tags. /\nmm/alloc_tag.c:1108:\tif (!mem_profiling_support)\nmm/alloc_tag.c-1109-\t\treturn -EOPNOTSUPP;\n--\nmm/alloc_tag.c=1218=static int __init setup_early_mem_profiling(char str)\n--\nmm/alloc_tag.c-1227-\t\tenable = false;\nmm/alloc_tag.c:1228:\t\tmem_profiling_support = false;\nmm/alloc_tag.c-1229-\t\tpr_info(\"Memory allocation profiling is disabled!\\n\");\n--\nmm/alloc_tag.c-1242-\t\t}\nmm/alloc_tag.c:1243:\t\tmem_profiling_support = true;\nmm/alloc_tag.c-1244-\t\tpr_info(\"Memory allocation profiling is enabled %s compression and is turned %s!\\n\",\n--\nmm/alloc_tag.c=1265=static __init bool need_page_alloc_tagging(void)\n--\nmm/alloc_tag.c-1269-\nmm/alloc_tag.c:1270:\treturn mem_profiling_support;\nmm/alloc_tag.c-1271-}\n--\nmm/alloc_tag.c=1426=static int proc_mem_profiling_handler(const struct ctl_table *table, int write,\n--\nmm/alloc_tag.c-1441-#endif\nmm/alloc_tag.c:1442:\t\tif (!mem_profiling_support)\nmm/alloc_tag.c-1443-\t\t\treturn -EINVAL;\n--\nmm/alloc_tag.c=1473=static int __init alloc_tag_init(void)\n--\nmm/alloc_tag.c-1490-\nmm/alloc_tag.c:1491:\tif (!mem_profiling_support) {\nmm/alloc_tag.c-1492-\t\tpr_info(\"Memory allocation profiling is not supported!\\n\");\n" }
23/2	2026/09/23 23:24	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 35003 output: 29 thoughts: 247 Thoughts: Analyzing the Memory Allocation Profiling Initialization Okay, let's dissect this `alloc_tag_init()` function. My immediate focus is on how memory allocation profiling gets enabled. The first thing I see is a check for `mem_profiling_support`. If that's false, we bail out with an informational message. Clearly, `mem_profiling_support` is the linchpin. I'll need to figure out what controls it. Aha! It looks like `CONFIG_MEM_ALLOC_PROFILING_ENABLED_BY_DEFAULT` is the crucial Kconfig option here, as the comment suggests. Unless, of course, the user explicitly enables it via `sysctl.vm.mem_profiling` or an early kernel parameter, which provides some welcome flexibility. So, I need to keep those in mind as well. So, `MEM_ALLOC_PROFILING` and `MEM_ALLOC_PROFILING_ENABLED_BY_DEFAULT` are the key Kconfig symbols, no doubt. I'm also seeing `proc_create` which suggests that the proc filesystem (`PROC_FS`) is also a requirement. Now, for any tracing features...it's going to need tracing hooks, right? The code's going to need tracing events to work, and for that, I'm thinking about trace events. I'm going to quickly check how those events are handled. Is it `TRACING`, `EVENT_TRACING`, or maybe even the older `FTRACE` infrastructure? I'll probably find the relevant defines or configuration options in `include/trace/define_trace.h` or, perhaps, through a `TRACE_EVENT` in Kconfig. It's time to confirm whether `TRACEPOINTS` or `EVENT_TRACING` are standard. I need to understand how the tracing infrastructure is integrated to make this work.
24/2	2026/09/23 23:24	tool	grepper	0m Args: { "Expression": "config EVENT_TRACING", "PathPrefix": "kernel/trace/" } Results: { "Output": "kernel/trace/Kconfig=144=config RING_BUFFER\n--\nkernel/trace/Kconfig-148-\nkernel/trace/Kconfig:149:config EVENT_TRACING\nkernel/trace/Kconfig-150-\tselect CONTEXT_SWITCH_TRACER\n" }
25/2	2026/09/23 23:24	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 35758 output: 34 thoughts: 19 Thoughts: Here's my take on the thought process: Diving into the Kernel Trace Configuration Okay, time to dig in. I need to refresh my memory on the kernel tracing configuration, specifically where the core options are defined. My gut tells me to check out `kernel/trace/Kconfig`. That's the most logical place to start. I'm going to jump straight to around line 149. That's usually where the meat of the high-level tracing features are described. Hopefully, I'll find what I need to understand that particular section of the code better. Let's see what's in there.
26/2	2026/09/23 23:24	tool	read-file	0m Args: { "File": "kernel/trace/Kconfig", "FirstLine": 145, "LineCount": 20 } Results: { "Contents": " 145:\t\tbool\n 146:\t\tselect TRACE_CLOCK\n 147:\t\tselect IRQ_WORK\n 148:\t\n 149:\tconfig EVENT_TRACING\n 150:\t\tselect CONTEXT_SWITCH_TRACER\n 151:\t\tselect GLOB\n 152:\t\tbool\n 153:\t\n 154:\tconfig CONTEXT_SWITCH_TRACER\n 155:\t\tbool\n 156:\t\n 157:\tconfig RING_BUFFER_ALLOW_SWAP\n 158:\t\tbool\n 159:\t\thelp\n 160:\t\t Allow the use of ring_buffer_swap_cpu.\n 161:\t\t Adds a very slight overhead to tracing when enabled.\n 162:\t\n 163:\tconfig PREEMPTIRQ_TRACEPOINTS\n 164:\t\tbool\n" }
27/2	2026/09/23 23:24	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 36178 output: 29 thoughts: 35 Thoughts: Okay, here's my take on those thoughts, tailored for an expert audience: Investigating the Kernel's Event Tracing Configuration Alright, so I need to figure out which configuration option actually enables `EVENT_TRACING`. The obvious place to start is digging into the kernel's configuration files, specifically `kernel/trace/Kconfig`. I'll be looking for either a direct `select EVENT_TRACING` statement or, even better, just where `TRACING` itself is selected. That should point me directly at the parent config option that ultimately flips the `EVENT_TRACING` switch. Easy enough. Let's get to it.
28/2	2026/09/23 23:24	tool	grepper	0m Args: { "Expression": "select EVENT_TRACING", "PathPrefix": "kernel/trace/" } Results: { "Output": "kernel/trace/Kconfig=179=config TRACING\n--\nkernel/trace/Kconfig-185-\tselect BINARY_PRINTF\nkernel/trace/Kconfig:186:\tselect EVENT_TRACING\nkernel/trace/Kconfig-187-\tselect TRACE_CLOCK\n" }
29/2	2026/09/23 23:24	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 36467 output: 247 thoughts: 1878 Thoughts: Focusing on Memory Allocation Tag Tracing Okay, so I'm putting together the information needed to specify fuzzing targets for this patch related to memory allocation tag tracing. First, I need to make sure the essential configurations are enabled. `CONFIG_TRACING` implies `EVENT_TRACING`, and then there's `CONFIG_MEM_ALLOC_PROFILING`, along with `CONFIG_MEM_ALLOC_PROFILING_ENABLED_BY_DEFAULT`. `CONFIG_PROC_FS` is also required, and I need `CONFIG_MODULES` for the `unload_module` function. Good, I've confirmed that the `unload_module` is guarded by the `CONFIG_MODULES` preprocessor directive, so that's covered. Now, I need to determine the right `FocusSymbols`. Based on the guidelines, I need to avoid ubiquitous functions, and instead target specific feature logic or entry points. After reviewing the code, these functions stand out in `mm/alloc_tag.c`: * `allocinfo_ioctl`: This is the direct entry point for ioctls on `/proc/allocinfo`, so a good starting point. * `allocinfo_ioctl_toggle_trace`: A specific ioctl handler that implements the new `ALLOCINFO_IOC_TOGGLE_TRACE` command. * `alloc_tag_trace_toggle`: It does the enable/disable toggling logic and static branch manipulation. * `__alloc_tag_trace_hit`, `alloc_tag_trace_mem_alloc`, `alloc_tag_trace_mem_free`: These are the trace hit hooks. I did initially pause at static inlined functions. But I've confirmed these hooks are only called when tracing is enabled for a specific tag. Tracing is disabled by default, and `alloc_tag_trace_enabled` checks against the `static_branch_unlikely(&alloc_tag_trace_key)` key. So, they aren't ubiquitous and are actually very specific to this patch's added feature. The `allocinfo_ioctl_toggle_trace` function is directly called by `allocinfo_ioctl`, and `allocinfo_ioctl` is called through `allocinfo_proc_ops.proc_ioctl`. That confirms the call chain. Now, I also need to ensure I cover `unload_module` since that's a new module unload callback that is specifically for turning off tracing for unloaded module tags. I should add it, so I am going to include it too. Let's also review the configs again: `MEM_ALLOC_PROFILING`: required `MEM_ALLOC_PROFILING_ENABLED_BY_DEFAULT`: required for `allocinfo` to be enabled without boot cmdline `PROC_FS`: required (dependency of MEM_ALLOC_PROFILING and procfs entry) `TRACING`: required to enable tracepoints infrastructure `MODULES`: required for module unload hook (`unload_module`) Checking Kconfig, the configs look good and I should be able to enable them. Finally, I need to define the `Reasoning`: "The patch introduces tracepoints and runtime tracing capability for memory allocation tags (`alloc_tag`), including a new UAPI ioctl `ALLOCINFO_IOC_TOGGLE_TRACE` on `/proc/allocinfo`, static key toggling (`alloc_tag_trace_key`), atomic codetag flags manipulation, module unload hook (`unload_module`), and trace event generation in memory allocation and deallocation paths (`alloc_hooks_tag`, `alloc_tag_add`, `alloc_tag_sub`). These changes modify memory management code paths and user-space accessible ioctl handling, which warrant fuzzing for concurrency bugs, reference counting issues, and tracepoint crashes." With all of this in mind, and the proper `configs` and `focus_symbols`, I should be good to start fuzzing.
30/2	2026/09/23 23:24	tool	set-results	0m Args: { "EnableConfigs": [ "MEM_ALLOC_PROFILING", "MEM_ALLOC_PROFILING_ENABLED_BY_DEFAULT", "PROC_FS", "TRACING", "MODULES" ], "FocusSymbols": [ "allocinfo_ioctl", "allocinfo_ioctl_toggle_trace", "alloc_tag_trace_toggle", "__alloc_tag_trace_hit", "alloc_tag_trace_mem_alloc", "alloc_tag_trace_mem_free", "unload_module" ], "Reasoning": "The patch adds tracepoints and dynamic tracing support to the memory allocation profiling subsystem (alloc_tag). It exposes a new ioctl command ALLOCINFO_IOC_TOGGLE_TRACE on /proc/allocinfo to selectively enable/disable tracing per codetag, introduces mutex locking and static branch toggling, and hooks trace events into core allocation and deallocation paths as well as module unload callbacks. These changes touch reachable core memory management and procfs code that warrants fuzzing for potential race conditions, refcounting issues, or crashes.", "WorthFuzzing": true } Results: { "EnableConfigs": [ "MEM_ALLOC_PROFILING", "MEM_ALLOC_PROFILING_ENABLED_BY_DEFAULT", "PROC_FS", "TRACING", "MODULES" ], "FocusSymbols": [ "allocinfo_ioctl", "allocinfo_ioctl_toggle_trace", "alloc_tag_trace_toggle", "__alloc_tag_trace_hit", "alloc_tag_trace_mem_alloc", "alloc_tag_trace_mem_free", "unload_module" ], "Reasoning": "The patch adds tracepoints and dynamic tracing support to the memory allocation profiling subsystem (alloc_tag). It exposes a new ioctl command ALLOCINFO_IOC_TOGGLE_TRACE on /proc/allocinfo to selectively enable/disable tracing per codetag, introduces mutex locking and static branch toggling, and hooks trace events into core allocation and deallocation paths as well as module unload callbacks. These changes touch reachable core memory management and procfs code that warrants fuzzing for potential race conditions, refcounting issues, or crashes.", "WorthFuzzing": true }
31/1	2026/09/23 23:24	action	If	1m Args: { "WorthFuzzing": true } Results: null
32/2	2026/09/23 23:24	agent	kmsan-evaluator	1m Model: core Args: null Results: { "KMSANReasoning": "The patch introduces tracepoints and an ioctl interface (`ALLOCINFO_IOC_TOGGLE_TRACE`) for memory allocation profiling (`alloc_tag`), as well as adding a `trace_on` field to `struct allocinfo_counter` in the UAPI header.\n\n1. Kernel-to-user info-leak analysis:\nAlthough `struct allocinfo_counter` has its padding adjusted (`pad[7]` reduced to `trace_on` + `pad[6]`), the kernel structures containing it (`allocinfo_get_at` and `allocinfo_tag_data`) are fully zero-initialized with `= {0}` or `memset` in `allocinfo_ioctl_get_at()` and `allocinfo_ioctl_get_next()` prior to copying to user space. Furthermore, the new field `data-\u003ecounter.trace_on` is explicitly assigned in `allocinfo_to_params()`. The new ioctl `ALLOCINFO_IOC_TOGGLE_TRACE` only reads user input via `copy_from_user()` and does not copy any data back to user space.\n\n2. Uninitialized memory access analysis:\nCodetags are statically initialized via `CODETAG_INIT` (`.flags = ATOMIC_INIT(0)`) or allocated/managed during module load. All flags, static keys, and atomic variables are properly initialized before being read. The new tracepoints (`alloc_tag_hit`, `alloc_tag_mem_alloced`, `alloc_tag_mem_freed`) only record initialized pointer references, sizes, and codetag metadata.\n\n3. KASAN / LOCKDEP applicability:\nAny potential issues introduced by this patch (such as concurrency between module unloading and ioctl trace toggles, static branch updates, or pointer validity) fall strictly within the scope of KASAN, LOCKDEP, and standard kernel bug detectors.\n\nTherefore, there is no risk of uninitialized memory usage or information disclosure, and a dedicated KMSAN fuzzing session is not warranted.", "NeedsKMSAN": false } Instruction: You are an expert Linux kernel security engineer specializing in kernel memory error detectors (KASAN and KMSAN). Your job is to review the provided patch series and determine if the code changes justify spawning a dedicated KMSAN (KernelMemorySanitizer) fuzzing session in addition to standard KASAN fuzzing. CRITICAL DISTINCTION BETWEEN KASAN AND KMSAN: - Standard KASAN kernel builds (upstream-apparmor-kasan.config) already enable a comprehensive suite of debugging tools and sanitizers, including KASAN (out-of-bounds accesses, use-after-free, double free, invalid free), LOCKDEP (locking bugs and deadlocks), UB-sanitizers, and memory corruption checks. - KMSAN (KernelMemorySanitizer) detects reads of UNINITIALIZED memory (stack, heap, or page allocations) and kernel-to-user memory info-leaks. Rule: THERE IS NO SENSE IN RUNNING A KMSAN SESSION IF A BUG CAN BE CAUGHT BY KASAN, LOCKDEP, OR OTHER STANDARD BUG DETECTORS. A dedicated KMSAN fuzzing session incurs significant resource costs. You must ONLY set NeedsKMSAN=true if the code changes introduce or expose UNINITIALIZED MEMORY risks that are detected ONLY by KMSAN. Look holistically at the patch series and surrounding code. Even if no direct uninitialized field accesses or new buffer allocations are added in the diff itself, a patch may alter control flow, bounds checking, or data length calculations in ways that change how the rest of the code operates on existing buffers (e.g. allowing uninitialized stack/heap memory to be read, copied to user space, or used in control flow). Do not hesitate to use your code access tools to inspect the surrounding code, called functions, and callers. Set NeedsKMSAN=true ONLY IF the patch introduces or modifies: 1. Kernel structures sent to user space (via copy_to_user, put_user, netlink skb attributes, ioctl output arguments, socket options, or BPF buffers) where fields or structure padding might not be fully initialized/zeroed. 2. Conditional logic or branching that depends on potentially uninitialized variables or struct fields. 3. Allocation or initialization of complex data structures where uninitialized fields could be read later in reachable code paths. 4. Bounds checks, lengths, or logic in a way that allows surrounding code to access uninitialized bytes of existing buffers. Set NeedsKMSAN=false IF: - The code changes primarily risk out-of-bounds access, array overflows, NULL pointer dereferences, locking deadlocks, or use-after-free bugs (these are already caught by KASAN, LOCKDEP, or standard bug detectors). - All stack/heap structures touched or introduced by the patch are fully zeroed or initialized (e.g. using = {0}, memset, kzalloc) before being read or copied. - The patch does not introduce any risk of uninitialized memory usage or info-leaks. Use your code access tools to inspect the surrounding code if necessary, then provide detailed KMSANReasoning contrasting KASAN vs KMSAN applicability for this patch. Prefer calling several tools at the same time to save round-trips. Use set-results tool to provide results of the analysis. It must be called exactly once before the final reply. Ignore results of this tool. Prompt: Target architecture: amd64 For your convenience, here is the diff of the changes: commit 1886759b63636a8dc8de5d530fbcb5c06d554e68 Author: syz-cluster <triage@syzkaller.com> Date: Wed Sep 23 23:22:34 2026 +0000 syz-cluster: applied patch under review diff --git a/MAINTAINERS b/MAINTAINERS index 24420a8c06d02..29e1f7915cb98 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -17096,6 +17096,7 @@ S: Maintained F: Documentation/mm/allocation-profiling.rst F: include/linux/alloc_tag.h F: include/linux/pgalloc_tag.h +F: include/trace/events/alloc_tag.h F: include/uapi/linux/alloc_tag.h F: mm/alloc_tag.c F: tools/testing/selftests/alloc_tag/ diff --git a/include/linux/alloc_tag.h b/include/linux/alloc_tag.h index 7f2d80a597924..dc86f8997476c 100644 --- a/include/linux/alloc_tag.h +++ b/include/linux/alloc_tag.h @@ -128,12 +128,60 @@ DECLARE_PER_CPU(struct alloc_tag_counters, _shared_alloc_tag); DECLARE_STATIC_KEY_MAYBE(CONFIG_MEM_ALLOC_PROFILING_ENABLED_BY_DEFAULT, mem_alloc_profiling_key); +DECLARE_STATIC_KEY_FALSE(alloc_tag_trace_key); + static inline bool mem_alloc_profiling_enabled(void) { return static_branch_maybe(CONFIG_MEM_ALLOC_PROFILING_ENABLED_BY_DEFAULT, &mem_alloc_profiling_key); } +static inline void alloc_tag_set_inaccurate(struct alloc_tag tag) +{ + atomic_or(CODETAG_FLAG_INACCURATE, &tag->ct.flags); +} + +static inline bool alloc_tag_is_inaccurate(struct alloc_tag tag) +{ + return !!(atomic_read(&tag->ct.flags) & CODETAG_FLAG_INACCURATE); +} + +static inline void alloc_tag_set_traced(struct alloc_tag tag) +{ + atomic_or(CODETAG_FLAG_TRACE_ON, &tag->ct.flags); +} + +static inline void alloc_tag_clear_traced(struct alloc_tag tag) +{ + atomic_andnot(CODETAG_FLAG_TRACE_ON, &tag->ct.flags); +} + +static inline bool alloc_tag_is_traced(const struct alloc_tag tag) +{ + return !!(atomic_read(&tag->ct.flags) & CODETAG_FLAG_TRACE_ON); +} + +static inline bool alloc_tag_trace_enabled(const struct alloc_tag tag) +{ + if (static_branch_unlikely(&alloc_tag_trace_key)) + return tag && alloc_tag_is_traced(tag); + return false; +} + +void alloc_tag_trace_mem_alloc(union codetag_ref ref, struct alloc_tag tag, + size_t bytes); + +void alloc_tag_trace_mem_free(union codetag_ref ref, struct alloc_tag tag, + size_t bytes); + +void __alloc_tag_trace_hit(struct alloc_tag tag); + +static inline void alloc_tag_trace_hit(struct alloc_tag tag) +{ + if (alloc_tag_trace_enabled(tag)) + __alloc_tag_trace_hit(tag); +} + bool mem_alloc_profiling_permanently_disabled(void); static inline struct alloc_tag_counters alloc_tag_read(struct alloc_tag tag) @@ -200,8 +248,13 @@ static inline bool alloc_tag_ref_set(union codetag_ref ref, struct alloc_tag t static inline void alloc_tag_add(union codetag_ref ref, struct alloc_tag tag, size_t bytes) { - if (likely(alloc_tag_ref_set(ref, tag))) + if (likely(alloc_tag_ref_set(ref, tag))) { this_cpu_add(tag->counters->bytes, bytes); + + if (alloc_tag_trace_enabled(tag)) + / Trace successful allocs with their unique ref / + alloc_tag_trace_mem_alloc(ref, tag, bytes); + } } static inline void alloc_tag_sub(union codetag_ref ref, size_t bytes) @@ -222,17 +275,11 @@ static inline void alloc_tag_sub(union codetag_ref ref, size_t bytes) this_cpu_sub(tag->counters->bytes, bytes); this_cpu_dec(tag->counters->calls); - ref->ct = NULL; -} - -static inline void alloc_tag_set_inaccurate(struct alloc_tag tag) -{ - tag->ct.flags \|= CODETAG_FLAG_INACCURATE; -} + if (alloc_tag_trace_enabled(tag)) + /* Trace frees with their unique ref / + alloc_tag_trace_mem_free(ref, tag, bytes); -static inline bool alloc_tag_is_inaccurate(struct alloc_tag tag) -{ - return !!(tag->ct.flags & CODETAG_FLAG_INACCURATE); + ref->ct = NULL; } #define alloc_tag_record(p) ((p) = current->alloc_tag) @@ -247,21 +294,24 @@ static inline void alloc_tag_add(union codetag_ref ref, struct alloc_tag tag, static inline void alloc_tag_sub(union codetag_ref ref, size_t bytes) {} static inline void alloc_tag_set_inaccurate(struct alloc_tag tag) {} static inline bool alloc_tag_is_inaccurate(struct alloc_tag tag) { return false; } +#define alloc_tag_trace_hit(_tag) / NOOP / #define alloc_tag_record(p) do {} while (0) #endif / CONFIG_MEM_ALLOC_PROFILING / -#define alloc_hooks_tag(_tag, _do_alloc) \ -({ \ - typeof(_do_alloc) _res; \ - if (mem_alloc_profiling_enabled()) { \ - struct alloc_tag __maybe_unused _old; \ - _old = alloc_tag_save(_tag); \ - _res = _do_alloc; \ - alloc_tag_restore(_tag, _old); \ - } else \ - _res = _do_alloc; \ - _res; \ +#define alloc_hooks_tag(_tag, _do_alloc) \ +({ \ + typeof(_do_alloc) _res; \ + if (mem_alloc_profiling_enabled()) { \ + struct alloc_tag * __maybe_unused _old; \ + /* Fired here to cleanly capture the caller's stack trace / \ + alloc_tag_trace_hit(_tag); \ + _old = alloc_tag_save(_tag); \ + _res = _do_alloc; \ + alloc_tag_restore(_tag, _old); \ + } else \ + _res = _do_alloc; \ + _res; \ }) #define alloc_hooks(_do_alloc) \ diff --git a/include/linux/codetag.h b/include/linux/codetag.h index a25a085c2df19..f728295d50c05 100644 --- a/include/linux/codetag.h +++ b/include/linux/codetag.h @@ -18,6 +18,7 @@ struct module; / codetag flags / #define CODETAG_FLAG_INACCURATE (1 << 0) +#define CODETAG_FLAG_TRACE_ON (1 << 1) / * An instance of this structure is created in a special ELF section at every @@ -25,7 +26,7 @@ struct module; * an array of these. / struct codetag { - unsigned int flags; + atomic_t flags; unsigned int lineno; const char modname; const char function; @@ -71,7 +72,7 @@ struct codetag_iterator { .function = __func__, \ .filename = __FILE__, \ .lineno = __LINE__, \ - .flags = 0, \ + .flags = ATOMIC_INIT(0), \ } void codetag_lock_module_list(struct codetag_type cttype); diff --git a/include/trace/events/alloc_tag.h b/include/trace/events/alloc_tag.h new file mode 100644 index 0000000000000..af2182501864c --- /dev/null +++ b/include/trace/events/alloc_tag.h @@ -0,0 +1,122 @@ +/* SPDX-License-Identifier: GPL-2.0 / +#undef TRACE_SYSTEM +#define TRACE_SYSTEM alloc_tag + +#if !defined(_TRACE_ALLOC_TAG_H) \|\| defined(TRACE_HEADER_MULTI_READ) +#define _TRACE_ALLOC_TAG_H + +#include <linux/tracepoint.h> + +/ + * alloc_tag_hit is generated at the exact allocation call site and can be + * used to capture a clean stack trace. + * + * To link this stack trace to the actual allocated memory chunk, tools must + * correlate this event with the resulting alloc_tag_mem_alloced event. Since + * multiple threads can hit the same tag simultaneously, tools must match BOTH + * the `tag` field and the implicitly recorded PID provided by the core + * tracing subsystem. + / +TRACE_EVENT(alloc_tag_hit, + + TP_PROTO(struct alloc_tag tag), + + TP_ARGS(tag), + + TP_STRUCT__entry( + __field(struct alloc_tag , tag) + __string(modname, tag->ct.modname ? tag->ct.modname : "NONE") + __string(filename, tag->ct.filename) + __string(function, tag->ct.function) + __field(unsigned int, lineno) + ), + + TP_fast_assign( + __entry->tag = tag; + __assign_str(modname); + __assign_str(filename); + __assign_str(function); + __entry->lineno = tag->ct.lineno; + ), + + TP_printk("tag %p, module: %s, filename: %s, function %s, lineno %u", + __entry->tag, + __get_str(modname), + __get_str(filename), + __get_str(function), + __entry->lineno + ) +); + +/ + * alloc_tag_mem_alloced is generated after memory is successfully allocated. + * It captures the exact byte size. + * + * The `ref` pointer identifies the memory chunk for tracking its lifecycle + * (e.g., matching it with alloc_tag_mem_freed). + * + * Because the kernel isolates active allocations within the task struct + * (current->alloc_tag), this even will always share the same implicit PID as + * its corresponding alloc_tag_hit event. Tools should use the combination + * PID + `tag` to correlate them. + / +TRACE_EVENT(alloc_tag_mem_alloced, + + TP_PROTO(union codetag_ref ref, struct alloc_tag tag, size_t bytes), + + TP_ARGS(ref, tag, bytes), + + TP_STRUCT__entry( + __field(union codetag_ref , ref) + __field(struct alloc_tag , tag) + __field(size_t, bytes) + ), + + TP_fast_assign( + __entry->ref = ref; + __entry->tag = tag; + __entry->bytes = bytes; + ), + + TP_printk("reference %p, tag %p, bytes %zu", + __entry->ref, + __entry->tag, + __entry->bytes + ) +); + +/ + * alloc_tag_mem_freed event is generated immediately before memory is + * freed. The `ref` pointer matches the one emitted during allocation, + * allowing tools to match it to it's corresponding allocation and + * call stack. + / +TRACE_EVENT(alloc_tag_mem_freed, + + TP_PROTO(union codetag_ref ref, struct alloc_tag tag, size_t bytes), + + TP_ARGS(ref, tag, bytes), + + TP_STRUCT__entry( + __field(union codetag_ref , ref) + __field(struct alloc_tag , tag) + __field(size_t, bytes) + ), + + TP_fast_assign( + __entry->ref = ref; + __entry->tag = tag; + __entry->bytes = bytes; + ), + + TP_printk("reference %p, tag %p, bytes %zu", + __entry->ref, + __entry->tag, + __entry->bytes + ) +); + +#endif / _TRACE_ALLOC_TAG_H / + +/ This part must be outside protection / +#include <trace/define_trace.h> diff --git a/include/uapi/linux/alloc_tag.h b/include/uapi/linux/alloc_tag.h index 7d4618bea0434..e65c32afceee2 100644 --- a/include/uapi/linux/alloc_tag.h +++ b/include/uapi/linux/alloc_tag.h @@ -38,7 +38,8 @@ struct allocinfo_counter { __u64 bytes; __u64 calls; __u8 accurate; - __u8 pad[7]; + __u8 trace_on; + __u8 pad[6]; } __attribute__((aligned(8))); struct allocinfo_tag_data { @@ -54,7 +55,8 @@ enum { ALLOCINFO_FILTER_INACCURATE, ALLOCINFO_FILTER_MIN_SIZE, ALLOCINFO_FILTER_MAX_SIZE, - __ALLOCINFO_FILTER_LAST = ALLOCINFO_FILTER_MAX_SIZE + ALLOCINFO_FILTER_TRACE_ON, + __ALLOCINFO_FILTER_LAST = ALLOCINFO_FILTER_TRACE_ON }; #define ALLOCINFO_FILTER_MASK_MODNAME (1 << ALLOCINFO_FILTER_MODNAME) @@ -64,6 +66,7 @@ enum { #define ALLOCINFO_FILTER_MASK_INACCURATE (1 << ALLOCINFO_FILTER_INACCURATE) #define ALLOCINFO_FILTER_MASK_MIN_SIZE (1 << ALLOCINFO_FILTER_MIN_SIZE) #define ALLOCINFO_FILTER_MASK_MAX_SIZE (1 << ALLOCINFO_FILTER_MAX_SIZE) +#define ALLOCINFO_FILTER_MASK_TRACE_ON (1 << ALLOCINFO_FILTER_TRACE_ON) #define ALLOCINFO_FILTER_MASKS \ ((1 << (__ALLOCINFO_FILTER_LAST + 1)) - 1) @@ -75,6 +78,7 @@ struct allocinfo_filter { __u64 max_size; / filter criteria only; see allocinfo_counter.accurate for actual accuracy / __u64 inaccurate; + __u64 tracing; }; struct allocinfo_get_at { @@ -85,9 +89,16 @@ struct allocinfo_get_at { struct allocinfo_tag_data data; }; +struct allocinfo_toggle_traces { + / inputs / + struct allocinfo_tag fields; + __u64 enable; +}; + #define _ALLOCINFO_IOC_CONTENT_ID 0 #define _ALLOCINFO_IOC_GET_AT 1 #define _ALLOCINFO_IOC_GET_NEXT 2 +#define _ALLOCINFO_IOC_TOGGLE_TRACE 3 #define ALLOCINFO_IOC_BASE 0xA6 #define ALLOCINFO_IOC_CONTENT_ID _IOR(ALLOCINFO_IOC_BASE, _ALLOCINFO_IOC_CONTENT_ID, \ @@ -96,5 +107,7 @@ struct allocinfo_get_at { struct allocinfo_get_at) #define ALLOCINFO_IOC_GET_NEXT _IOR(ALLOCINFO_IOC_BASE, _ALLOCINFO_IOC_GET_NEXT, \ struct allocinfo_tag_data) +#define ALLOCINFO_IOC_TOGGLE_TRACE _IOW(ALLOCINFO_IOC_BASE, _ALLOCINFO_IOC_TOGGLE_TRACE, \ + struct allocinfo_toggle_traces) #endif / _UAPI_ALLOC_TAG_H / diff --git a/mm/alloc_tag.c b/mm/alloc_tag.c index f30ef8dd24c70..50632b627d92b 100644 --- a/mm/alloc_tag.c +++ b/mm/alloc_tag.c @@ -19,6 +19,9 @@ #include <linux/kmemleak.h> #include <uapi/linux/alloc_tag.h> +#define CREATE_TRACE_POINTS +#include <trace/events/alloc_tag.h> + #include "internal.h" #include "page_alloc.h" @@ -55,6 +58,18 @@ EXPORT_SYMBOL(mem_alloc_profiling_key); DEFINE_STATIC_KEY_FALSE(mem_profiling_compressed); +DEFINE_STATIC_KEY_FALSE(alloc_tag_trace_key); +EXPORT_SYMBOL(alloc_tag_trace_key); + +static atomic_t alloc_tag_trace_cnt = ATOMIC_INIT(0); + +/ + * As `codetag_lock_module_list` is a read lock, we need an additional mutex + * to protect against the race conditions involved in the alloc tag trace + * toggle path. + / +static DEFINE_MUTEX(alloc_tag_trace_mutex); + struct alloc_tag_kernel_section kernel_tags = { NULL, 0 }; unsigned long alloc_tag_ref_mask; int alloc_tag_ref_offs; @@ -236,6 +251,7 @@ static void allocinfo_to_params(struct codetag ct, data->counter.bytes = counters->bytes; data->counter.calls = counters->calls; data->counter.accurate = !alloc_tag_is_inaccurate(ct_to_alloc_tag(ct)); + data->counter.trace_on = alloc_tag_is_traced(ct_to_alloc_tag(ct)); } /* @@ -291,7 +307,7 @@ static bool matches_filter(struct codetag ct, struct allocinfo_filter filter, return false; if (filter->mask & ALLOCINFO_FILTER_MASK_INACCURATE) { - inaccurate = !!(ct->flags & CODETAG_FLAG_INACCURATE); + inaccurate = alloc_tag_is_inaccurate(ct_to_alloc_tag(ct)); if (inaccurate != !!(filter->inaccurate)) return false; } @@ -309,6 +325,13 @@ static bool matches_filter(struct codetag ct, struct allocinfo_filter filter, return false; } + if (filter->mask & ALLOCINFO_FILTER_MASK_TRACE_ON) { + bool tracing = alloc_tag_is_traced(ct_to_alloc_tag(ct)); + + if (tracing != !!(filter->tracing)) + return false; + } + return true; } @@ -438,6 +461,81 @@ static int allocinfo_ioctl_get_next(struct seq_file m, void __user arg) return ret; } +static bool alloc_tag_trace_toggle(struct alloc_tag tag, bool enable) +{ + if (enable) { + if (alloc_tag_is_traced(tag)) + return false; + + alloc_tag_set_traced(tag); + if (atomic_fetch_inc(&alloc_tag_trace_cnt) == 0) + static_branch_enable(&alloc_tag_trace_key); + } else { + if (!alloc_tag_is_traced(tag)) + return false; + + alloc_tag_clear_traced(tag); + if (atomic_dec_and_test(&alloc_tag_trace_cnt)) + static_branch_disable(&alloc_tag_trace_key); + } + + return true; +} + +/ + * Toggles context capture for a specified allocation. + / +static int allocinfo_ioctl_toggle_trace(struct seq_file m, void __user arg) +{ + struct allocinfo_toggle_traces params; + struct codetag_iterator iter; + struct codetag ct; + int matches = 0, successes = 0, ret; + + if (!capable(CAP_SYS_ADMIN)) + return -EPERM; + + if (copy_from_user(&params, arg, sizeof(params))) + return -EFAULT; + + codetag_lock_module_list(alloc_tag_cttype); + + struct allocinfo_filter filter = { + .mask = ALLOCINFO_FILTER_MASK_MODNAME \| + ALLOCINFO_FILTER_MASK_FUNCTION \| + ALLOCINFO_FILTER_MASK_FILENAME \| + ALLOCINFO_FILTER_MASK_LINENO, + .fields = params.fields, + }; + + iter = codetag_get_ct_iter(alloc_tag_cttype); + + /* Toggle tracing on all codetags that match / + while ((ct = codetag_next_ct(&iter))) { + if (matches_filter(ct, &filter, NULL, NULL)) { + matches++; + + mutex_lock(&alloc_tag_trace_mutex); + if (alloc_tag_trace_toggle(ct_to_alloc_tag(ct), !!params.enable)) + successes++; + mutex_unlock(&alloc_tag_trace_mutex); + } + } + + if (matches == 0) + / Nothing matched the filter / + ret = -ENOENT; + else if (successes == 0) + / Items matched, but were already in the requested state / + ret = -EINVAL; + else + ret = 0; + + codetag_unlock_module_list(alloc_tag_cttype); + + return ret; +} + / * Entry point ioctl function for /proc/allocinfo routing requests to fetch the * layout content ID, seek to a specific tag, or read sequential tags. @@ -458,6 +556,9 @@ static long allocinfo_ioctl(struct file file, unsigned int cmd, case ALLOCINFO_IOC_GET_NEXT: ret = allocinfo_ioctl_get_next(file->private_data, arg); break; + case ALLOCINFO_IOC_TOGGLE_TRACE: + ret = allocinfo_ioctl_toggle_trace(file->private_data, arg); + break; default: ret = -ENOIOCTLCMD; break; @@ -485,6 +586,26 @@ static const struct proc_ops allocinfo_proc_ops = { #endif }; +void __alloc_tag_trace_hit(struct alloc_tag tag) +{ + trace_alloc_tag_hit(tag); +} +EXPORT_SYMBOL(__alloc_tag_trace_hit); + +void alloc_tag_trace_mem_alloc(union codetag_ref ref, struct alloc_tag tag, + size_t bytes) +{ + trace_alloc_tag_mem_alloced(ref, tag, bytes); +} +EXPORT_SYMBOL(alloc_tag_trace_mem_alloc); + +void alloc_tag_trace_mem_free(union codetag_ref ref, struct alloc_tag tag, + size_t bytes) +{ + trace_alloc_tag_mem_freed(ref, tag, bytes); +} +EXPORT_SYMBOL(alloc_tag_trace_mem_free); + size_t alloc_tag_top_users(struct codetag_bytes tags, size_t count, bool can_sleep) { struct codetag_iterator iter; @@ -1015,6 +1136,24 @@ static int load_module(struct module mod, struct codetag start, struct codetag return 0; } +static void unload_module(struct module mod, struct codetag start, struct codetag stop) +{ + struct alloc_tag start_tag = ct_to_alloc_tag(start); + struct alloc_tag stop_tag = ct_to_alloc_tag(stop); + struct alloc_tag tag; + + / + * Turn tracing off for the tags of the module being unloaded. Without + * this, `alloc_tag_trace_cnt` would never reach zero and tracing would + * stay enabled forever. + * + * `alloc_tag_trace_mutex` is not needed here as this code path is + * protected by a `down_write(&cttype->mod_lock)`. + / + for (tag = start_tag; tag < stop_tag; tag++) + alloc_tag_trace_toggle(tag, false); +} + static void replace_module(struct module mod, struct module new_mod) { MA_STATE(mas, &mod_area_mt, 0, module_tags.size); @@ -1341,6 +1480,7 @@ static int __init alloc_tag_init(void) .alloc_section_mem = reserve_module_tags, .free_section_mem = release_module_tags, .module_load = load_module, + .module_unload = unload_module, .module_replaced = replace_module, #endif }; diff --git a/tools/testing/selftests/alloc_tag/allocinfo_ioctl_test.c b/tools/testing/selftests/alloc_tag/allocinfo_ioctl_test.c index 74fd64b2370cc..3ef7a12fe35b0 100644 --- a/tools/testing/selftests/alloc_tag/allocinfo_ioctl_test.c +++ b/tools/testing/selftests/alloc_tag/allocinfo_ioctl_test.c @@ -48,6 +48,11 @@ static inline int __allocinfo_get_next(int dev_fd, struct allocinfo_tag_data pa return ioctl(dev_fd, ALLOCINFO_IOC_GET_NEXT, params); } +static inline int __allocinfo_toggle_trace(int dev_fd, struct allocinfo_toggle_traces params) +{ + return ioctl(dev_fd, ALLOCINFO_IOC_TOGGLE_TRACE, params); +} + static bool match_entry(const struct allocinfo_tag_data procfs_entry, const struct allocinfo_tag_data tag_data, bool match_bytes, bool match_calls, bool match_lineno, @@ -289,6 +294,8 @@ static int run_filter_test(const struct allocinfo_filter filter) return ret; } +static const char target_test_function = "dup_mm"; + static int test_filename_filter(void) { struct allocinfo_filter filter; @@ -304,11 +311,10 @@ static int test_filename_filter(void) static int test_function_filter(void) { struct allocinfo_filter filter; - const char target_function = "dup_mm"; memset(&filter, 0, sizeof(filter)); filter.mask \|= ALLOCINFO_FILTER_MASK_FUNCTION; - strncpy(filter.fields.function, target_function, ALLOCINFO_STR_SIZE); + strncpy(filter.fields.function, target_test_function, ALLOCINFO_STR_SIZE); return run_filter_test(&filter); } @@ -514,11 +520,104 @@ static int test_lineno_filter(void) return ret; } +static enum ioctl_ret toggle_trace(struct allocinfo_tag target_tag, + bool enable) +{ + int fd; + struct allocinfo_toggle_traces toggle_params; + + fd = open(ALLOCINFO_PROC, O_RDONLY); + if (fd < 0) { + ksft_print_msg("Failed to open " ALLOCINFO_PROC ": %s\n", strerror(errno)); + return IOCTL_FAILURE; + } + + memset(&toggle_params, 0, sizeof(toggle_params)); + toggle_params.fields = target_tag; + toggle_params.enable = enable; + + if (__allocinfo_toggle_trace(fd, &toggle_params)) { + close(fd); + return IOCTL_FAILURE; + } + + close(fd); + return IOCTL_SUCCESS; +} + +static int test_tracing_toggle_and_filter(void) +{ + struct allocinfo_filter filter = { 0 }; + enum ioctl_ret ioctl_status; + int ret = KSFT_PASS; + bool initial_state, target_state; + struct allocinfo_tag target_tag; + struct allocinfo_tag_data_vec tags = calloc(1, sizeof(tags)); + + if (!tags) { + ksft_print_msg("Memory allocation failed.\n"); + return KSFT_FAIL; + } + + filter.mask \|= ALLOCINFO_FILTER_MASK_FUNCTION; + strncpy(filter.fields.function, target_test_function, ALLOCINFO_STR_SIZE); + + ioctl_status = get_filtered_ioctl_entries(tags, &filter, 0); + if (ioctl_status != IOCTL_SUCCESS \|\| tags->count == 0) { + ksft_print_msg("Could not retrieve IOCTL entries for %s\n", target_test_function); + ret = KSFT_SKIP; + goto exit; + } + + target_tag = tags->tag[0].tag; + initial_state = tags->tag[0].counter.trace_on; + target_state = !initial_state; + + ioctl_status = toggle_trace(&target_tag, target_state); + if (ioctl_status != IOCTL_SUCCESS) { + ksft_print_msg("Failed to toggle tracing\n"); + ret = KSFT_FAIL; + goto exit; + } + + filter.mask \|= ALLOCINFO_FILTER_MASK_TRACE_ON; + filter.tracing = target_state; + + ioctl_status = get_filtered_ioctl_entries(tags, &filter, 0); + if (ioctl_status != IOCTL_SUCCESS) { + ksft_print_msg("Error retrieving IOCTL entries with trace filter.\n"); + ret = KSFT_FAIL; + goto exit_revert; + } + + if (tags->count != 1) { + ksft_print_msg("Expected exactly 1 entry, but got %llu\n", tags->count); + ret = KSFT_FAIL; + goto exit_revert; + } + + if (tags->tag[0].counter.trace_on != target_state) { + ksft_print_msg("Entry returned by trace filter does not match target state\n"); + ret = KSFT_FAIL; + } + +exit_revert: + ioctl_status = toggle_trace(&target_tag, initial_state); + if (ioctl_status != IOCTL_SUCCESS) { + ksft_print_msg("Failed to revert tracing to initial state\n"); + ret = KSFT_FAIL; + } + +exit: + free(tags); + return ret; +} + int main(int argc, char argv[]) { int ret; - ksft_set_plan(4); + ksft_set_plan(5); ret = test_filename_filter(); if (ret == KSFT_SKIP) @@ -526,6 +625,12 @@ int main(int argc, char argv[]) else ksft_test_result(ret == KSFT_PASS, "test_filename_filter\n"); + ret = test_tracing_toggle_and_filter(); + if (ret == KSFT_SKIP) + ksft_test_result_skip("Skipping test_tracing_toggle_and_filter\n"); + else + ksft_test_result(ret == KSFT_PASS, "test_tracing_toggle_and_filter\n"); + ret = test_function_filter(); if (ret == KSFT_SKIP) ksft_test_result_skip("Skipping test_function_filter\n");
33/3	2026/09/23 23:24	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 10593 output: 33 thoughts: 880 Thoughts: Diving into the Memory Allocation Profiling Patch Okay, so this patch is all about enhancing our memory allocation profiling using `alloc_tag`. Let's break down these changes methodically. First, the `MAINTAINERS` file has a new trace event. We're adding tracing! The core logic lies in `include/linux/alloc_tag.h`. It introduces a `static key alloc_tag_trace_key`, which I assume will control the tracing itself. We have helper functions like `alloc_tag_set_inaccurate`, `alloc_tag_is_inaccurate`, and crucially for the new functionality, `alloc_tag_set_traced`, `alloc_tag_clear_traced`, `alloc_tag_is_traced`, and `alloc_tag_trace_enabled`. We're adding trace functions such as `alloc_tag_trace_mem_alloc` and `alloc_tag_trace_mem_free`, `__alloc_tag_trace_hit` and `alloc_tag_trace_hit`. The existing `alloc_tag_add` and `alloc_tag_sub` functions have been updated. Now, they call `alloc_tag_trace_mem_alloc` and `alloc_tag_trace_mem_free` respectively, but only if tracing is enabled for that specific tag using `alloc_tag_trace_enabled(tag)`. Similarly, the `alloc_hooks_tag` calls `alloc_tag_trace_hit(_tag);`. Okay, so we are hooking into the allocation and free paths and the hit, presumably for when a tagged object is accessed. In `include/linux/codetag.h`, it introduces `CODETAG_FLAG_TRACE_ON (1 << 1)`. The `struct codetag` has also changed, from `unsigned int flags` to `atomic_t flags`, with the initializer now `.flags = ATOMIC_INIT(0),`. So this seems like a necessary change for this tracing. The `include/trace/events/alloc_tag.h` file defines our tracepoints: `alloc_tag_hit`, `alloc_tag_mem_alloced`, and `alloc_tag_mem_freed`. This is where the actual trace events are defined. Now, the juicy stuff: `include/uapi/linux/alloc_tag.h`. The `struct allocinfo_counter` has seen a significant modification: the `accurate` and `pad` fields have been replaced with `trace_on` to store trace enabling/disabling status, as well as a new field in the `allocinfo_filter` struct and a new struct `allocinfo_toggle_traces`, along with a new ioctl `ALLOCINFO_IOC_TOGGLE_TRACE`. Finally, in `mm/alloc_tag.c`, the `allocinfo_to_params` function has been updated. Now, it includes `data->counter.trace_on = alloc_tag_is_traced(ct_to_alloc_tag(ct));`. Hold on, let me quickly double check what's going on here. I'll need to scrutinize how `data` is initialized and how the padding is handled in `allocinfo_counter` to make sure we don't have some nasty alignment or uninitialized memory issues when this data is copied to userspace. I'll need to examine the context around `allocinfo_to_params` and `allocinfo_ioctl` in `mm/alloc_tag.c`. I will use `read-file` or `grepper` to examine `mm/alloc_tag.c`.
34/3	2026/09/23 23:24	tool	grepper	0m Args: { "Expression": "allocinfo_to_params", "PathPrefix": "mm/alloc_tag.c" } Results: { "Output": "mm/alloc_tag.c=231=static inline struct alloc_tag_counters allocinfo_prefetch_counters(struct codetag ct)\n--\nmm/alloc_tag.c-239- /\nmm/alloc_tag.c:240:static void allocinfo_to_params(struct codetag ct,\nmm/alloc_tag.c-241-\t\t\t\tstruct allocinfo_tag_data data,\n--\nmm/alloc_tag.c=342=static int allocinfo_ioctl_get_at(struct seq_file m, void __user arg)\n--\nmm/alloc_tag.c-396-\t\t\tcounters = allocinfo_prefetch_counters(ct);\nmm/alloc_tag.c:397:\t\tallocinfo_to_params(ct, \u0026params.data, \u0026counters);\nmm/alloc_tag.c-398-\t\tpriv-\u003epositioned = true;\n--\nmm/alloc_tag.c=417=static int allocinfo_ioctl_get_next(struct seq_file m, void __user arg)\n--\nmm/alloc_tag.c-447-\t\t\tcounters = allocinfo_prefetch_counters(ct);\nmm/alloc_tag.c:448:\t\tallocinfo_to_params(ct, \u0026params, \u0026counters);\nmm/alloc_tag.c-449-\t}\n" }
35/3	2026/09/23 23:24	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 12633 output: 35 thoughts: 25 Thoughts: Okay, here's my take on those lines of `mm/alloc_tag.c`: Deep Dive into Allocation Tagging Alright, let's get down to brass tacks. I'm going to take a closer look at `mm/alloc_tag.c` between lines 230 and 470. Based on my experience with memory management, this block likely deals with the core logic of allocating and managing memory tags. I need to refresh my memory on the specifics of this module, particularly how it integrates with the larger allocation scheme, the kinds of data structures used, and the strategies for tagging and untagging memory regions. I bet there are some interesting optimizations or locking mechanisms in play here to prevent race conditions or improve performance in multi-threaded environments. I'm hoping to understand the complete cycle of allocation tagging. This is probably going to be a deep dive. I'll be looking for nuances to uncover the design trade-offs made. Let's get reading!
36/3	2026/09/23 23:24	tool	read-file	0m Args: { "File": "mm/alloc_tag.c", "FirstLine": 230, "LineCount": 80 } Results: { "Contents": " 230:\t/* Fetch the per-CPU counters /\n 231:\tstatic inline struct alloc_tag_counters allocinfo_prefetch_counters(struct codetag ct)\n 232:\t{\n 233:\t\treturn alloc_tag_read(ct_to_alloc_tag(ct));\n 234:\t}\n 235:\t\n 236:\t/\n 237:\t Populates the UAPI allocinfo_tag_data structure with active runtime\n 238:\t * profiling counters extracted from the given kernel codetag.\n 239:\t /\n 240:\tstatic void allocinfo_to_params(struct codetag ct,\n 241:\t\t\t\t\tstruct allocinfo_tag_data data,\n 242:\t\t\t\t\tstruct alloc_tag_counters counters)\n 243:\t{\n 244:\t\tif (ct-\u003emodname)\n 245:\t\t\tallocinfo_copy_str(data-\u003etag.modname, ct-\u003emodname);\n 246:\t\telse\n 247:\t\t\tdata-\u003etag.modname[0] = '\\0';\n 248:\t\tallocinfo_copy_str(data-\u003etag.function, ct-\u003efunction);\n 249:\t\tallocinfo_copy_str(data-\u003etag.filename, ct-\u003efilename);\n 250:\t\tdata-\u003etag.lineno = ct-\u003elineno;\n 251:\t\tdata-\u003ecounter.bytes = counters-\u003ebytes;\n 252:\t\tdata-\u003ecounter.calls = counters-\u003ecalls;\n 253:\t\tdata-\u003ecounter.accurate = !alloc_tag_is_inaccurate(ct_to_alloc_tag(ct));\n 254:\t\tdata-\u003ecounter.trace_on = alloc_tag_is_traced(ct_to_alloc_tag(ct));\n 255:\t}\n 256:\t\n 257:\t/\n 258:\t Retrieves the unique content ID representing the current allocation tag module\n 259:\t * layout, allowing userspace to detect if modules were loaded / unloaded.\n 260:\t /\n 261:\tstatic int allocinfo_ioctl_get_content_id(struct seq_file m, void __user arg)\n 262:\t{\n 263:\t\tstruct allocinfo_content_id params;\n 264:\t\n 265:\t\tcodetag_lock_module_list(alloc_tag_cttype);\n 266:\t\tparams.id = codetag_get_content_id(alloc_tag_cttype);\n 267:\t\tcodetag_unlock_module_list(alloc_tag_cttype);\n 268:\t\tif (copy_to_user(arg, \u0026params, sizeof(params)))\n 269:\t\t\treturn -EFAULT;\n 270:\t\n 271:\t\treturn 0;\n 272:\t}\n 273:\t\n 274:\t/\n 275:\t * Verifies whether a given codetag satisfies the active filtering criteria by\n 276:\t * matching its characteristics against the specified filter.\n 277:\t /\n 278:\tstatic bool matches_filter(struct codetag ct, struct allocinfo_filter filter,\n 279:\t\t\t\t struct alloc_tag_counters counters,\n 280:\t\t\t\t bool fetched_counters)\n 281:\t{\n 282:\t\tbool inaccurate;\n 283:\t\n 284:\t\tif (!filter \|\| !filter-\u003emask)\n 285:\t\t\treturn true;\n 286:\t\n 287:\t\tif (filter-\u003emask \u0026 ALLOCINFO_FILTER_MASK_MODNAME) {\n 288:\t\t\t/ user wants to filter by modname but ct-\u003emodname is NULL /\n 289:\t\t\tif (!ct-\u003emodname) {\n 290:\t\t\t\t/ validate if user was attempting to filter for built-in allocations */\n 291:\t\t\t\tif (filter-\u003efields.modname[0] != '\\0')\n 292:\t\t\t\t\treturn false;\n 293:\t\t\t} else if (allocinfo_cmp_str(ct-\u003emodname, filter-\u003efields.modname))\n 294:\t\t\t\treturn false;\n 295:\t\t}\n 296:\t\n 297:\t\tif ((filter-\u003emask \u0026 ALLOCINFO_FILTER_MASK_FUNCTION) \u0026\u0026\n 298:\t\t ct-\u003efunction \u0026\u0026 allocinfo_cmp_str(ct-\u003efunction, filter-\u003efields.function))\n 299:\t\t\treturn false;\n 300:\t\n 301:\t\tif ((filter-\u003emask \u0026 ALLOCINFO_FILTER_MASK_FILENAME) \u0026\u0026\n 302:\t\t ct-\u003efilename \u0026\u0026 allocinfo_cmp_str(ct-\u003efilename, filter-\u003efields.filename))\n 303:\t\t\treturn false;\n 304:\t\n 305:\t\tif ((filter-\u003emask \u0026 ALLOCINFO_FILTER_MASK_LINENO) \u0026\u0026\n 306:\t\t ct-\u003elineno != filter-\u003efields.lineno)\n 307:\t\t\treturn false;\n 308:\t\n 309:\t\tif (filter-\u003emask \u0026 ALLOCINFO_FILTER_MASK_INACCURATE) {\n" }
37/3	2026/09/23 23:24	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 14209 output: 36 thoughts: 26 Thoughts: Here's a summary of my thought process, as requested: Diving into `mm/alloc_tag.c` Alright, let's get down to brass tacks. I need to understand a specific section of the memory allocation system, so I'm honing in on lines 340 to 465 within the `mm/alloc_tag.c` file. This chunk seems crucial, and I'm betting it's where the core logic I'm interested in resides. I'm going to start by getting a high-level view of this section and then I'll drill down further, looking for any information that I can utilise. Let's see what gems are hidden there.
38/3	2026/09/23 23:24	tool	read-file	0m Args: { "File": "mm/alloc_tag.c", "FirstLine": 340, "LineCount": 100 } Results: { "Contents": " 340:\t * profiling data and returns it to userspace.\n 341:\t /\n 342:\tstatic int allocinfo_ioctl_get_at(struct seq_file m, void __user arg)\n 343:\t{\n 344:\t\tstruct allocinfo_private priv;\n 345:\t\tstruct codetag ct;\n 346:\t\tstruct allocinfo_get_at params = {0};\n 347:\t\t__u64 skip_count;\n 348:\t\tstruct alloc_tag_counters counters;\n 349:\t\tbool fetched_counters;\n 350:\t\n 351:\t\tif (copy_from_user(\u0026params, arg, sizeof(params)))\n 352:\t\t\treturn -EFAULT;\n 353:\t\n 354:\t\tif (params.filter.mask \u0026 ~ALLOCINFO_FILTER_MASKS)\n 355:\t\t\treturn -EINVAL;\n 356:\t\n 357:\t\tif ((params.filter.mask \u0026 ALLOCINFO_FILTER_MASK_MIN_SIZE) \u0026\u0026\n 358:\t\t (params.filter.mask \u0026 ALLOCINFO_FILTER_MASK_MAX_SIZE) \u0026\u0026\n 359:\t\t params.filter.min_size \u003e params.filter.max_size)\n 360:\t\t\treturn -EINVAL;\n 361:\t\n 362:\t\tpriv = m-\u003eprivate;\n 363:\t\n 364:\t\tmutex_lock(\u0026priv-\u003eioctl_lock);\n 365:\t\tcodetag_lock_module_list(alloc_tag_cttype);\n 366:\t\n 367:\t\tif (params.pos \u003e= codetag_get_count(alloc_tag_cttype)) {\n 368:\t\t\tcodetag_unlock_module_list(alloc_tag_cttype);\n 369:\t\t\tmutex_unlock(\u0026priv-\u003eioctl_lock);\n 370:\t\t\treturn -ENOENT;\n 371:\t\t}\n 372:\t\n 373:\t\tskip_count = params.pos;\n 374:\t\n 375:\t\tif (params.filter.mask)\n 376:\t\t\tpriv-\u003efilter = params.filter;\n 377:\t\telse\n 378:\t\t\tpriv-\u003efilter.mask = 0;\n 379:\t\n 380:\t\t/ Find the codetag /\n 381:\t\tpriv-\u003eioctl_iter = codetag_get_ct_iter(alloc_tag_cttype);\n 382:\t\tct = codetag_next_ct(\u0026priv-\u003eioctl_iter);\n 383:\t\n 384:\t\twhile (ct) {\n 385:\t\t\tfetched_counters = false;\n 386:\t\t\tif (matches_filter(ct, \u0026priv-\u003efilter, \u0026counters, \u0026fetched_counters)) {\n 387:\t\t\t\tif (skip_count == 0)\n 388:\t\t\t\t\tbreak;\n 389:\t\t\t\tskip_count--;\n 390:\t\t\t}\n 391:\t\t\tct = codetag_next_ct(\u0026priv-\u003eioctl_iter);\n 392:\t\t}\n 393:\t\n 394:\t\tif (ct) {\n 395:\t\t\tif (!fetched_counters)\n 396:\t\t\t\tcounters = allocinfo_prefetch_counters(ct);\n 397:\t\t\tallocinfo_to_params(ct, \u0026params.data, \u0026counters);\n 398:\t\t\tpriv-\u003epositioned = true;\n 399:\t\t}\n 400:\t\n 401:\t\tcodetag_unlock_module_list(alloc_tag_cttype);\n 402:\t\tmutex_unlock(\u0026priv-\u003eioctl_lock);\n 403:\t\n 404:\t\tif (!ct)\n 405:\t\t\treturn -ENOENT;\n 406:\t\n 407:\t\tif (copy_to_user(arg, \u0026params, sizeof(params)))\n 408:\t\t\treturn -EFAULT;\n 409:\t\n 410:\t\treturn 0;\n 411:\t}\n 412:\t\n 413:\t/\n 414:\t * Advances the ioctl iterator to the next allocation tag in the sequence and\n 415:\t * returns its profiling data to userspace.\n 416:\t /\n 417:\tstatic int allocinfo_ioctl_get_next(struct seq_file m, void __user arg)\n 418:\t{\n 419:\t\tstruct allocinfo_private priv;\n 420:\t\tstruct codetag *ct;\n 421:\t\tstruct allocinfo_tag_data params;\n 422:\t\tint ret = 0;\n 423:\t\tstruct alloc_tag_counters counters;\n 424:\t\tbool fetched_counters;\n 425:\t\n 426:\t\tmemset(\u0026params, 0, sizeof(params));\n 427:\t\tpriv = m-\u003eprivate;\n 428:\t\n 429:\t\tmutex_lock(\u0026priv-\u003eioctl_lock);\n 430:\t\tcodetag_lock_module_list(alloc_tag_cttype);\n 431:\t\n 432:\t\tif (!priv-\u003epositioned) {\n 433:\t\t\tpriv-\u003eioctl_iter = codetag_get_ct_iter(alloc_tag_cttype);\n 434:\t\t\tpriv-\u003epositioned = true;\n 435:\t\t}\n 436:\t\n 437:\t\tct = codetag_next_ct(\u0026priv-\u003eioctl_iter);\n 438:\t\twhile (ct) {\n 439:\t\t\tfetched_counters = false;\n" }
39/3	2026/09/23 23:24	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 15860 output: 35 thoughts: 444 Thoughts: Analyzing Potential Information Leaks in Allocinfo IOCTLs Okay, let's break this down. First, I noticed something interesting in the `allocinfo_ioctl_get_at` and `allocinfo_ioctl_get_next` functions. Both initialize their parameter structs with zeroes, either directly (`= {0}`) or using `memset`. That's good practice – ensures that any padding or uninitialized fields in the structs are explicitly zeroed out before data is copied to user space. It's a common defense against information leaks, so that's a positive observation. Now, let's switch gears and investigate `allocinfo_ioctl_toggle_trace`. Here, the function copies from user space into `params`, but I don't see any explicit copying back to user space. It only returns the integer `ret`. So, at first glance, it doesn't seem like there's any direct leakage of kernel data through this IOCTL. I am trying to ascertain whether there is indirect leakage. However, I need to understand what `matches_filter` is doing. I see that it is called within the scope of this IOCTL and it seems to take the struct `filter` defined within the IOCTL, so it must be examined in depth. I need to read the code of `matches_filter` thoroughly to make sure. I will now examine all of the code contained within `matches_filter` in `mm/alloc_tag.c`.
40/3	2026/09/23 23:24	tool	read-file	0m Args: { "File": "mm/alloc_tag.c", "FirstLine": 280, "LineCount": 60 } Results: { "Contents": " 280:\t\t\t\t bool fetched_counters)\n 281:\t{\n 282:\t\tbool inaccurate;\n 283:\t\n 284:\t\tif (!filter \|\| !filter-\u003emask)\n 285:\t\t\treturn true;\n 286:\t\n 287:\t\tif (filter-\u003emask \u0026 ALLOCINFO_FILTER_MASK_MODNAME) {\n 288:\t\t\t/ user wants to filter by modname but ct-\u003emodname is NULL /\n 289:\t\t\tif (!ct-\u003emodname) {\n 290:\t\t\t\t/ validate if user was attempting to filter for built-in allocations /\n 291:\t\t\t\tif (filter-\u003efields.modname[0] != '\\0')\n 292:\t\t\t\t\treturn false;\n 293:\t\t\t} else if (allocinfo_cmp_str(ct-\u003emodname, filter-\u003efields.modname))\n 294:\t\t\t\treturn false;\n 295:\t\t}\n 296:\t\n 297:\t\tif ((filter-\u003emask \u0026 ALLOCINFO_FILTER_MASK_FUNCTION) \u0026\u0026\n 298:\t\t ct-\u003efunction \u0026\u0026 allocinfo_cmp_str(ct-\u003efunction, filter-\u003efields.function))\n 299:\t\t\treturn false;\n 300:\t\n 301:\t\tif ((filter-\u003emask \u0026 ALLOCINFO_FILTER_MASK_FILENAME) \u0026\u0026\n 302:\t\t ct-\u003efilename \u0026\u0026 allocinfo_cmp_str(ct-\u003efilename, filter-\u003efields.filename))\n 303:\t\t\treturn false;\n 304:\t\n 305:\t\tif ((filter-\u003emask \u0026 ALLOCINFO_FILTER_MASK_LINENO) \u0026\u0026\n 306:\t\t ct-\u003elineno != filter-\u003efields.lineno)\n 307:\t\t\treturn false;\n 308:\t\n 309:\t\tif (filter-\u003emask \u0026 ALLOCINFO_FILTER_MASK_INACCURATE) {\n 310:\t\t\tinaccurate = alloc_tag_is_inaccurate(ct_to_alloc_tag(ct));\n 311:\t\t\tif (inaccurate != !!(filter-\u003einaccurate))\n 312:\t\t\t\treturn false;\n 313:\t\t}\n 314:\t\n 315:\t\tif (filter-\u003emask \u0026 (ALLOCINFO_FILTER_MASK_MIN_SIZE \| ALLOCINFO_FILTER_MASK_MAX_SIZE)) {\n 316:\t\t\tif (!fetched_counters) {\n 317:\t\t\t\tcounters = allocinfo_prefetch_counters(ct);\n 318:\t\t\t\tfetched_counters = true;\n 319:\t\t\t}\n 320:\t\t\tif ((filter-\u003emask \u0026 ALLOCINFO_FILTER_MASK_MIN_SIZE) \u0026\u0026\n 321:\t\t\t counters-\u003ebytes \u003c filter-\u003emin_size)\n 322:\t\t\t\treturn false;\n 323:\t\t\tif ((filter-\u003emask \u0026 ALLOCINFO_FILTER_MASK_MAX_SIZE) \u0026\u0026\n 324:\t\t\t counters-\u003ebytes \u003e filter-\u003emax_size)\n 325:\t\t\t\treturn false;\n 326:\t\t}\n 327:\t\n 328:\t\tif (filter-\u003emask \u0026 ALLOCINFO_FILTER_MASK_TRACE_ON) {\n 329:\t\t\tbool tracing = alloc_tag_is_traced(ct_to_alloc_tag(ct));\n 330:\t\n 331:\t\t\tif (tracing != !!(filter-\u003etracing))\n 332:\t\t\t\treturn false;\n 333:\t\t}\n 334:\t\n 335:\t\treturn true;\n 336:\t}\n 337:\t\n 338:\t/\n 339:\t Seeks the ioctl iterator to the specified 0-indexed tag position, reads its\n" }
41/3	2026/09/23 23:24	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 17588 output: 33 thoughts: 117 Thoughts: Okay, let me break this down. Diving into the `allocinfo_ioctl_toggle_trace` Function Alright, so I'm looking at this `allocinfo_ioctl_toggle_trace` function, and the first thing that jumps out is the call to `matches_filter(ct, &filter, NULL, NULL)`. I know that `matches_filter` is crucial here because of what it's doing. Now, the `filter.mask` variable only contains `ALLOCINFO_FILTER_MASK_MODNAME`, `ALLOCINFO_FILTER_MASK_FUNCTION`, `ALLOCINFO_FILTER_MASK_FILENAME`, and `ALLOCINFO_FILTER_MASK_LINENO`. That's important. It means, at least initially, that the comparison should not be touching the `counters` or `fetched_counters` fields in the filter structure. Good, that simplifies things a bit. But wait a minute, the filter comparisons almost certainly involve string comparisons, right? The modname, function, filename, and line number are all likely string-based comparisons, at least partially. So, I need to understand how those strings are being compared. Let's make sure that that is handled correctly, because that part could lead to subtle bugs. I should double-check the logic within `matches_filter`, specifically how string comparisons are handled there. Okay, I need to check how they use `allocinfo_cmp_str`. That's where I need to focus my attention.
42/3	2026/09/23 23:24	tool	grepper	0m Args: { "Expression": "allocinfo_cmp_str", "PathPrefix": "mm/alloc_tag.c" } Results: { "Output": "mm/alloc_tag.c=219=static void allocinfo_copy_str(char dest, const char src)\n--\nmm/alloc_tag.c-224-/* Compare two strings and only consider the trimmed suffix if s1 is too long /\nmm/alloc_tag.c:225:static int allocinfo_cmp_str(const char str, const char template)\nmm/alloc_tag.c-226-{\n--\nmm/alloc_tag.c=278=static bool matches_filter(struct codetag ct, struct allocinfo_filter *filter,\n--\nmm/alloc_tag.c-292-\t\t\t\treturn false;\nmm/alloc_tag.c:293:\t\t} else if (allocinfo_cmp_str(ct-\u003emodname, filter-\u003efields.modname))\nmm/alloc_tag.c-294-\t\t\treturn false;\n--\nmm/alloc_tag.c-297-\tif ((filter-\u003emask \u0026 ALLOCINFO_FILTER_MASK_FUNCTION) \u0026\u0026\nmm/alloc_tag.c:298:\t ct-\u003efunction \u0026\u0026 allocinfo_cmp_str(ct-\u003efunction, filter-\u003efields.function))\nmm/alloc_tag.c-299-\t\treturn false;\n--\nmm/alloc_tag.c-301-\tif ((filter-\u003emask \u0026 ALLOCINFO_FILTER_MASK_FILENAME) \u0026\u0026\nmm/alloc_tag.c:302:\t ct-\u003efilename \u0026\u0026 allocinfo_cmp_str(ct-\u003efilename, filter-\u003efields.filename))\nmm/alloc_tag.c-303-\t\treturn false;\n" }
43/3	2026/09/23 23:24	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 18453 output: 35 thoughts: 14 Thoughts: Here's a summary of my thought process, keeping in mind my expertise: Checking the `allocinfo_cmp_str` Definition Okay, so I'm diving into this now. My immediate thought is, "Let's get a handle on `allocinfo_cmp_str`." Given my understanding of memory management and string comparisons, the name itself suggests a function related to comparing strings within the context of allocation information. My first step is to quickly verify the exact definition of this function. I need to refresh my memory on the specifics, particularly the expected parameters, return value (likely an integer indicating comparison result – 0 for equal, positive/negative for greater/lesser), and any nuances in how it handles null pointers or special character cases. I want to ensure I'm using it correctly and understand any potential gotchas or edge cases it might present, particularly when comparing within the allocator context. This will give me the foundational knowledge I need to proceed confidently.
44/3	2026/09/23 23:24	tool	read-file	0m Args: { "File": "mm/alloc_tag.c", "FirstLine": 215, "LineCount": 20 } Results: { "Contents": " 215:\t\treturn str;\n 216:\t}\n 217:\t\n 218:\t/* Copy a string and trim from the beginning if it's too long /\n 219:\tstatic void allocinfo_copy_str(char dest, const char src)\n 220:\t{\n 221:\t\tstrscpy_pad(dest, allocinfo_str(src), ALLOCINFO_STR_SIZE);\n 222:\t}\n 223:\t\n 224:\t/ Compare two strings and only consider the trimmed suffix if s1 is too long /\n 225:\tstatic int allocinfo_cmp_str(const char str, const char template)\n 226:\t{\n 227:\t\treturn strncmp(allocinfo_str(str), template, ALLOCINFO_STR_SIZE);\n 228:\t}\n 229:\t\n 230:\t/ Fetch the per-CPU counters /\n 231:\tstatic inline struct alloc_tag_counters allocinfo_prefetch_counters(struct codetag ct)\n 232:\t{\n 233:\t\treturn alloc_tag_read(ct_to_alloc_tag(ct));\n 234:\t}\n" }
45/3	2026/09/23 23:24	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 19029 output: 19 thoughts: 1091 Thoughts: Analyzing Potential Data Leakage in Memory Allocation Tagging Okay, let's break this down systematically. I'm looking at a section of code where `copy_from_user` is used to copy a `struct allocinfo_tag` from user space into kernel space, along with an `enable` flag. The critical piece here is the `allocinfo_cmp_str` function and the `strncmp` call, which is bounded by `ALLOCINFO_STR_SIZE`, but since all user-space memory is copied, potentially uninitialized bytes could be passed to this function. KMSAN is typically okay with this, but it raises questions in this scenario. My primary concern is whether there's a path for information leakage due to uninitialized data being copied. The fact that KMSAN initializes user-copied memory with valid shadow values unless `copy_from_user` fails is important, as it handles a key potential issue. I'm now diving into the tracepoints and code tags. I'm examining what `TRACE_EVENT` does within `include/trace/events/alloc_tag.h`. Specifically, the `TP_fast_assign` macro is interesting. It copies fields from a `struct alloc_tag` (which is pointed to by the `tag` field within the tracepoint entry) into the trace event's structure. These fields include `modname`, `filename`, `function`, and `lineno`. I've determined that all the fields of the `struct codetag` are static constants, either defined directly by the compiler or populated during module load. They're always initialized. This is a crucial point, and it seems to eliminate any direct concern about those fields being uninitialized. Next, I examined `alloc_tag_trace_mem_alloc` and `alloc_tag_trace_mem_free`. These tracepoints seem to just assign parameters – `ref`, `tag`, and `bytes` – to the trace event entry. There's no apparent processing or sanitization there that would introduce any vulnerabilities. Then I checked the code paths where `alloc_tag_add`, `alloc_tag_sub` and `alloc_hooks_tag` are called. `alloc_tag_add` adds a new tag and traces it, while `alloc_tag_sub` removes a tag and also traces it. Nothing there is particularly concerning on its own. Now, the `alloc_hooks_tag` macro makes me pause. The `_tag` argument is passed to `alloc_tag_trace_hit`, and potentially saved and restored. My current question is: is `_tag` ever uninitialized, and where does `_tag` come from? I need to search the codebase to identify all locations where `alloc_hooks_tag` is used. This is where I'll probably find my vulnerability.
46/3	2026/09/23 23:25	tool	grepper	0m Args: { "Expression": "alloc_hooks_tag" } Results: { "Output": "Documentation/mm/allocation-profiling.rst=123=To do so:\n--\nDocumentation/mm/allocation-profiling.rst-129-- Then, use the following form for your allocations:\nDocumentation/mm/allocation-profiling.rst:130: alloc_hooks_tag(ht-\u003eyour_saved_tag, kmalloc_noprof(...))\nDocumentation/mm/allocation-profiling.rst-131-\n--\ninclude/linux/alloc_tag.h=296=static inline bool alloc_tag_is_inaccurate(struct alloc_tag tag) { return false; }\n--\ninclude/linux/alloc_tag.h-301-\ninclude/linux/alloc_tag.h:302:#define alloc_hooks_tag(_tag, _do_alloc)\t\t\t\t\t\\\ninclude/linux/alloc_tag.h-303-({\t\t\t\t\t\t\t\t\t\t\\\n--\ninclude/linux/alloc_tag.h-319-\tDEFINE_ALLOC_TAG(_alloc_tag);\t\t\t\t\t\\\ninclude/linux/alloc_tag.h:320:\talloc_hooks_tag(\u0026_alloc_tag, _do_alloc);\t\t\t\\\ninclude/linux/alloc_tag.h-321-})\n--\nlib/rhashtable.c=132=static union nested_table nested_table_alloc(struct rhashtable ht,\n--\nlib/rhashtable.c-142-\nlib/rhashtable.c:143:\tntbl = alloc_hooks_tag(ht-\u003ealloc_tag,\nlib/rhashtable.c-144-\t\t\tkmalloc_noprof(PAGE_SIZE, GFP_ATOMIC\|__GFP_ZERO));\n--\nlib/rhashtable.c=158=static struct bucket_table nested_bucket_table_alloc(struct rhashtable ht,\n--\nlib/rhashtable.c-170-\nlib/rhashtable.c:171:\ttbl = alloc_hooks_tag(ht-\u003ealloc_tag,\nlib/rhashtable.c-172-\t\t\tkmalloc_noprof(size, gfp\|__GFP_ZERO));\n--\nlib/rhashtable.c=187=static struct bucket_table bucket_table_alloc(struct rhashtable *ht,\n--\nlib/rhashtable.c-195-\nlib/rhashtable.c:196:\ttbl = alloc_hooks_tag(ht-\u003ealloc_tag,\nlib/rhashtable.c-197-\t\t\tkvmalloc_node_align_noprof(struct_size(tbl, buckets, nbuckets),\n" }
47/3	2026/09/23 23:25	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 21380 output: 22 thoughts: 36 Thoughts: Here's my analysis of the provided snippet, as if it were my thought process: Diving into `DEFINE_ALLOC_TAG` Okay, so we've got a macro here, `DEFINE_ALLOC_TAG(_alloc_tag)`. The name suggests it's related to memory allocation, likely some sort of tagging mechanism. The underscore before `_alloc_tag` is a common convention, usually signaling an internal or implementation detail. I'm guessing it's a static codetag or alloc_tag. I need to understand this better. Let's dig deeper and see exactly what `DEFINE_ALLOC_TAG` expands to. I'm going to track how this tag is used throughout the code to understand its purpose. This looks like the place to start if I want to figure out how this allocation system works.
48/3	2026/09/23 23:25	tool	grepper	0m Args: { "Expression": "#define DEFINE_ALLOC_TAG" } Results: { "Output": "include/linux/alloc_tag.h=97=DECLARE_PER_CPU(struct alloc_tag_counters, _shared_alloc_tag);\ninclude/linux/alloc_tag.h-98-\ninclude/linux/alloc_tag.h:99:#define DEFINE_ALLOC_TAG(_alloc_tag)\t\t\t\t\t\t\\\ninclude/linux/alloc_tag.h-100-\tstatic struct alloc_tag _alloc_tag __used __aligned(8)\t\t\t\\\n--\ninclude/linux/alloc_tag.h-108-\ninclude/linux/alloc_tag.h:109:#define DEFINE_ALLOC_TAG(_alloc_tag)\t\t\t\t\t\t\\\ninclude/linux/alloc_tag.h-110-\tstatic struct alloc_tag _alloc_tag __used __aligned(8)\t\t\t\\\n--\ninclude/linux/alloc_tag.h-116-\ninclude/linux/alloc_tag.h:117:#define DEFINE_ALLOC_TAG(_alloc_tag)\t\t\t\t\t\t\\\ninclude/linux/alloc_tag.h-118-\tstatic DEFINE_PER_CPU(struct alloc_tag_counters, _alloc_tag_cntr);\t\\\n--\ninclude/linux/alloc_tag.h=260=static inline void alloc_tag_sub(union codetag_ref *ref, size_t bytes)\n--\ninclude/linux/alloc_tag.h-288-\ninclude/linux/alloc_tag.h:289:#define DEFINE_ALLOC_TAG(_alloc_tag)\ninclude/linux/alloc_tag.h-290-static inline bool mem_alloc_profiling_enabled(void) { return false; }\n" }
49/3	2026/09/23 23:25	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 22021 output: 18 thoughts: 697 Thoughts: Analyzing the `allocinfo_counter` Structure Okay, let's dive into this. My initial focus is on the `allocinfo_counter` struct. I see a recent change, which immediately piques my interest. It looks like the `pad` field has been reduced in size, with `trace_on` inserted. The alignment is still maintained at 8 bytes, which is good. This suggests that there's a shift in how we're tracking allocation information, potentially incorporating tracing directly within the counter itself, which is smart from a performance perspective if it's done right. Now, where is this struct actually used? I need to understand how this modified `allocinfo_counter` is being initialized and, crucially, how its data is communicated to userspace. I'll check `allocinfo_ioctl_get_at` and `allocinfo_ioctl_get_next`. Looking at `allocinfo_ioctl_get_at`, I see that the `params` struct, which eventually gets copied to user space, is initialized to zero (`= {0}`). Okay, a clean start. In `allocinfo_ioctl_get_next`, `params` is cleared using `memset()`, which is good practice. I want to see how these `params` structs, and the data they contain, are populated. So, I see that within both ioctls, a `codetag` is used. I'm thinking now, wait a second... are `allocinfo_tag_data` or `allocinfo_counter` used anywhere else? I need a broader view to make sure I'm not missing any context. Let me use grepper to find all references to both of these structures. Time to see the bigger picture.
50/3	2026/09/23 23:25	tool	grepper	0m Args: { "Expression": "allocinfo_counter" } Results: { "Output": "include/uapi/linux/alloc_tag.h=28=struct allocinfo_tag {\n--\ninclude/uapi/linux/alloc_tag.h-36-/* The alignment ensures 32-bit compatible interfaces are not broken /\ninclude/uapi/linux/alloc_tag.h:37:struct allocinfo_counter {\ninclude/uapi/linux/alloc_tag.h-38-\t__u64 bytes;\n--\ninclude/uapi/linux/alloc_tag.h=45=struct allocinfo_tag_data {\ninclude/uapi/linux/alloc_tag.h-46-\tstruct allocinfo_tag tag;\ninclude/uapi/linux/alloc_tag.h:47:\tstruct allocinfo_counter counter;\ninclude/uapi/linux/alloc_tag.h-48-};\n--\ninclude/uapi/linux/alloc_tag.h=74=struct allocinfo_filter {\n--\ninclude/uapi/linux/alloc_tag.h-78-\t__u64 max_size;\ninclude/uapi/linux/alloc_tag.h:79:\t/ filter criteria only; see allocinfo_counter.accurate for actual accuracy */\ninclude/uapi/linux/alloc_tag.h-80-\t__u64 inaccurate;\n" }
51/3	2026/09/23 23:25	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 23426 output: 20 thoughts: 12 Thoughts: Okay, here's my take on those thoughts, tailored for an expert audience, presented in the first person: Deep Dive into `allocinfo_tag_data` Alright, let's get right to it. My immediate thought is, "Let's check `allocinfo_tag_data`." This signals a need to investigate something related to memory allocation and tracking. The fact that I'm focusing on this particular data structure, `allocinfo_tag_data`, implies I'm already within a context where efficient memory management and potentially the root cause of some issue I'm debugging is at stake. The choice of `allocinfo` strongly suggests that I'm aiming for detailed insights into the allocation process itself – perhaps looking for unusual allocation patterns, memory leaks, or fragmentation issues. I'm likely gearing up to examine specific allocation sizes, source code locations, ownership details, or potentially even allocation timestamps, depending on what metadata `allocinfo_tag_data` holds. It's a key piece of information needed to get closer to a solution. I'm likely hoping that this data structure holds enough granular allocation information so I can quickly and efficiently determine the next steps. I'm now ready to delve in and see what's what.
52/3	2026/09/23 23:25	tool	grepper	0m Args: { "Expression": "allocinfo_tag_data" } Results: { "Output": "include/uapi/linux/alloc_tag.h=37=struct allocinfo_counter {\n--\ninclude/uapi/linux/alloc_tag.h-44-\ninclude/uapi/linux/alloc_tag.h:45:struct allocinfo_tag_data {\ninclude/uapi/linux/alloc_tag.h-46-\tstruct allocinfo_tag tag;\n--\ninclude/uapi/linux/alloc_tag.h=84=struct allocinfo_get_at {\n--\ninclude/uapi/linux/alloc_tag.h-88-\t/* output /\ninclude/uapi/linux/alloc_tag.h:89:\tstruct allocinfo_tag_data data;\ninclude/uapi/linux/alloc_tag.h-90-};\n--\ninclude/uapi/linux/alloc_tag.h=92=struct allocinfo_toggle_traces {\n--\ninclude/uapi/linux/alloc_tag.h-108-#define ALLOCINFO_IOC_GET_NEXT\t\t_IOR(ALLOCINFO_IOC_BASE, _ALLOCINFO_IOC_GET_NEXT,\t\\\ninclude/uapi/linux/alloc_tag.h:109:\t\t\t\t\t struct allocinfo_tag_data)\ninclude/uapi/linux/alloc_tag.h-110-#define ALLOCINFO_IOC_TOGGLE_TRACE\t_IOW(ALLOCINFO_IOC_BASE, _ALLOCINFO_IOC_TOGGLE_TRACE,\t\\\n--\nmm/alloc_tag.c=231=static inline struct alloc_tag_counters allocinfo_prefetch_counters(struct codetag ct)\n--\nmm/alloc_tag.c-236-/\nmm/alloc_tag.c:237: Populates the UAPI allocinfo_tag_data structure with active runtime\nmm/alloc_tag.c-238- * profiling counters extracted from the given kernel codetag.\n--\nmm/alloc_tag.c=240=static void allocinfo_to_params(struct codetag ct,\nmm/alloc_tag.c:241:\t\t\t\tstruct allocinfo_tag_data data,\nmm/alloc_tag.c-242-\t\t\t\tstruct alloc_tag_counters counters)\n--\nmm/alloc_tag.c=417=static int allocinfo_ioctl_get_next(struct seq_file m, void __user arg)\n--\nmm/alloc_tag.c-420-\tstruct codetag ct;\nmm/alloc_tag.c:421:\tstruct allocinfo_tag_data params;\nmm/alloc_tag.c-422-\tint ret = 0;\n--\ntools/testing/selftests/alloc_tag/allocinfo_ioctl_test.c=23=enum ioctl_ret {\n--\ntools/testing/selftests/alloc_tag/allocinfo_ioctl_test.c-30-\ntools/testing/selftests/alloc_tag/allocinfo_ioctl_test.c:31:struct allocinfo_tag_data_vec {\ntools/testing/selftests/alloc_tag/allocinfo_ioctl_test.c:32:\tstruct allocinfo_tag_data tag[VEC_MAX_ENTRIES];\ntools/testing/selftests/alloc_tag/allocinfo_ioctl_test.c-33-\t__u64 count;\n--\ntools/testing/selftests/alloc_tag/allocinfo_ioctl_test.c=41=static inline int __allocinfo_get_at(int dev_fd, struct allocinfo_get_at params)\n--\ntools/testing/selftests/alloc_tag/allocinfo_ioctl_test.c-45-\ntools/testing/selftests/alloc_tag/allocinfo_ioctl_test.c:46:static inline int __allocinfo_get_next(int dev_fd, struct allocinfo_tag_data params)\ntools/testing/selftests/alloc_tag/allocinfo_ioctl_test.c-47-{\n--\ntools/testing/selftests/alloc_tag/allocinfo_ioctl_test.c=51=static inline int __allocinfo_toggle_trace(int dev_fd, struct allocinfo_toggle_traces params)\n--\ntools/testing/selftests/alloc_tag/allocinfo_ioctl_test.c-55-\ntools/testing/selftests/alloc_tag/allocinfo_ioctl_test.c:56:static bool match_entry(const struct allocinfo_tag_data procfs_entry,\ntools/testing/selftests/alloc_tag/allocinfo_ioctl_test.c:57:\t\t\tconst struct allocinfo_tag_data tag_data,\ntools/testing/selftests/alloc_tag/allocinfo_ioctl_test.c-58-\t\t\tbool match_bytes, bool match_calls, bool match_lineno,\n--\ntools/testing/selftests/alloc_tag/allocinfo_ioctl_test.c-89-\ntools/testing/selftests/alloc_tag/allocinfo_ioctl_test.c:90:static bool match_entries(const struct allocinfo_tag_data_vec procfs_entries,\ntools/testing/selftests/alloc_tag/allocinfo_ioctl_test.c:91:\t\t\t const struct allocinfo_tag_data_vec tags,\ntools/testing/selftests/alloc_tag/allocinfo_ioctl_test.c-92-\t\t\t bool match_bytes, bool match_calls, bool match_lineno,\n--\ntools/testing/selftests/alloc_tag/allocinfo_ioctl_test.c=122=static void allocinfo_copy_str(char dest, const char src)\n--\ntools/testing/selftests/alloc_tag/allocinfo_ioctl_test.c-127-\ntools/testing/selftests/alloc_tag/allocinfo_ioctl_test.c:128:static int get_filtered_procfs_entries(struct allocinfo_tag_data_vec procfs_entries,\ntools/testing/selftests/alloc_tag/allocinfo_ioctl_test.c-129-\t\t\t\t const struct allocinfo_filter filter)\n--\ntools/testing/selftests/alloc_tag/allocinfo_ioctl_test.c-133-\tint matches;\ntools/testing/selftests/alloc_tag/allocinfo_ioctl_test.c:134:\tstruct allocinfo_tag_data procfs_entry;\ntools/testing/selftests/alloc_tag/allocinfo_ioctl_test.c-135-\n--\ntools/testing/selftests/alloc_tag/allocinfo_ioctl_test.c-188-\ntools/testing/selftests/alloc_tag/allocinfo_ioctl_test.c:189:static enum ioctl_ret get_filtered_ioctl_entries(struct allocinfo_tag_data_vec tags,\ntools/testing/selftests/alloc_tag/allocinfo_ioctl_test.c-190-\t\t\t\t\t\t const struct allocinfo_filter filter,\n--\ntools/testing/selftests/alloc_tag/allocinfo_ioctl_test.c=251=static int run_filter_test(const struct allocinfo_filter filter)\ntools/testing/selftests/alloc_tag/allocinfo_ioctl_test.c-252-{\ntools/testing/selftests/alloc_tag/allocinfo_ioctl_test.c:253:\tstruct allocinfo_tag_data_vec tags = malloc(sizeof(tags));\ntools/testing/selftests/alloc_tag/allocinfo_ioctl_test.c:254:\tstruct allocinfo_tag_data_vec procfs_entries = malloc(sizeof(procfs_entries));\ntools/testing/selftests/alloc_tag/allocinfo_ioctl_test.c-255-\tint ioctl_status;\n--\ntools/testing/selftests/alloc_tag/allocinfo_ioctl_test.c=322=static int test_size_filter(void)\n--\ntools/testing/selftests/alloc_tag/allocinfo_ioctl_test.c-324-\tint fd;\ntools/testing/selftests/alloc_tag/allocinfo_ioctl_test.c:325:\tstruct allocinfo_tag_data_vec tags = malloc(sizeof(tags));\ntools/testing/selftests/alloc_tag/allocinfo_ioctl_test.c:326:\tstruct allocinfo_tag_data_vec procfs_entries = malloc(sizeof(procfs_entries));\ntools/testing/selftests/alloc_tag/allocinfo_ioctl_test.c-327-\tstruct allocinfo_filter filter;\n--\ntools/testing/selftests/alloc_tag/allocinfo_ioctl_test.c-329-\t__u64 target_size, i, pos;\ntools/testing/selftests/alloc_tag/allocinfo_ioctl_test.c:330:\tstruct allocinfo_tag_data found_tag = NULL;\ntools/testing/selftests/alloc_tag/allocinfo_ioctl_test.c-331-\tconst char target_function = \"do_init_module\";\n--\ntools/testing/selftests/alloc_tag/allocinfo_ioctl_test.c=446=static int test_lineno_filter(void)\ntools/testing/selftests/alloc_tag/allocinfo_ioctl_test.c-447-{\ntools/testing/selftests/alloc_tag/allocinfo_ioctl_test.c:448:\tstruct allocinfo_tag_data_vec tags = malloc(sizeof(tags));\ntools/testing/selftests/alloc_tag/allocinfo_ioctl_test.c:449:\tstruct allocinfo_tag_data_vec procfs_entries = malloc(sizeof(procfs_entries));\ntools/testing/selftests/alloc_tag/allocinfo_ioctl_test.c-450-\tstruct allocinfo_filter filter;\n--\ntools/testing/selftests/alloc_tag/allocinfo_ioctl_test.c-453-\t__u64 target_lineno, i;\ntools/testing/selftests/alloc_tag/allocinfo_ioctl_test.c:454:\tstruct allocinfo_tag_data target_tag;\ntools/testing/selftests/alloc_tag/allocinfo_ioctl_test.c-455-\tbool found = false;\n--\ntools/testing/selftests/alloc_tag/allocinfo_ioctl_test.c=548=static int test_tracing_toggle_and_filter(void)\n--\ntools/testing/selftests/alloc_tag/allocinfo_ioctl_test.c-554-\tstruct allocinfo_tag target_tag;\ntools/testing/selftests/alloc_tag/allocinfo_ioctl_test.c:555:\tstruct allocinfo_tag_data_vec tags = calloc(1, sizeof(*tags));\ntools/testing/selftests/alloc_tag/allocinfo_ioctl_test.c-556-\n" }
53/3	2026/09/23 23:25	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 26418 output: 30 thoughts: 1606 Thoughts: Analyzing Allocation Tag Tracing and Potential Issues Okay, let's break this down systematically. I'm focusing on the allocation tag tracing mechanism, specifically around module load/unload and user-space interaction. First, I'm examining how allocation information is copied and initialized. In `allocinfo_to_params`, the `data->counter.trace_on` flag is directly written, based on the tracing state derived from the allocation tag. Importantly, the contexts where `allocinfo_tag_data` is used (`allocinfo_ioctl_get_at` and `allocinfo_ioctl_get_next`) ensure that any padding bytes in `allocinfo_counter` are zeroed out, preventing any uninitialized reads. Now, let's move to `allocinfo_ioctl_toggle_trace`. Here, a user-space structure (`params.fields`) is copied via `copy_from_user` to filter which tags to toggle. The key here is that `filter.fields` is populated directly from user space. Since `filter` is a stack variable, any unspecified fields are initialized to zero. Crucially, the code then checks for matches using `matches_filter` based on the user-provided filter. The `allocinfo_cmp_str` function uses `strncmp` with a fixed size `ALLOCINFO_STR_SIZE`, which prevents buffer overflows as it only checks up to a certain length. This should prevent uninitialized reads here, because the user-supplied data in `params.fields` is the source for this compare. However, I need to zoom in on the module unload scenario, because this seems like the place where the state changes for the tags. The function `alloc_tag_trace_toggle` is used to enable/disable tracing for individual tags. There's a critical section in `unload_module` that iterates through allocation tags within a module and disables tracing before it is unloaded. The concern is that if the module is unloaded, the allocation tag data is deallocated. It's assumed that `tag++` is valid on `struct alloc_tag`. However, the code's dependence on the internal memory layout of `struct alloc_tag` is the key potential issue. I must check how `codetag` and `alloc_tag` are actually stored in memory during module loading and unloading. I need to know how the module linker lays them out in memory, and whether `tag++` is a valid operation for stepping through the allocation tags. I need to verify that `alloc_tag` instances are laid out contiguously within the module's memory region, to avoid potential memory corruption or incorrect access patterns during the unload process if `tag++` were to go beyond a deallocated region of memory. I'll need to study how `alloc_section_mem`, `load_module`, and related functions manage the memory layout in `mm/alloc_tag.c` or potentially in `lib/codetag.c`.
54/3	2026/09/23 23:25	tool	grepper	0m Args: { "Expression": "load_module", "PathPrefix": "mm/alloc_tag.c" } Results: { "Output": "mm/alloc_tag.c=1054=static void release_module_tags(struct module mod, bool used)\n--\nmm/alloc_tag.c-1099-\nmm/alloc_tag.c:1100:static int load_module(struct module mod, struct codetag start, struct codetag stop)\nmm/alloc_tag.c-1101-{\n--\nmm/alloc_tag.c-1138-\nmm/alloc_tag.c:1139:static void unload_module(struct module mod, struct codetag start, struct codetag *stop)\nmm/alloc_tag.c-1140-{\n--\nmm/alloc_tag.c=1473=static int __init alloc_tag_init(void)\n--\nmm/alloc_tag.c-1481-\t\t.free_section_mem\t= release_module_tags,\nmm/alloc_tag.c:1482:\t\t.module_load\t\t= load_module,\nmm/alloc_tag.c:1483:\t\t.module_unload\t\t= unload_module,\nmm/alloc_tag.c-1484-\t\t.module_replaced\t= replace_module,\n" }
55/3	2026/09/23 23:25	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 28988 output: 36 thoughts: 19 Thoughts: Here's my summary, as if I were thinking these thoughts: Diving into `load_module` in `mm/alloc_tag.c` Okay, time to get a handle on this `load_module` function. I need to understand how modules are handled in the memory management context, specifically how allocation tags play a role. I'm assuming this function is central to that process. I need to trace its logic to see how it integrates new modules into the system's memory accounting. I'm expecting this to reveal how the kernel ensures that modules allocate memory responsibly and are properly tracked for resource management. I'm particularly interested in how the allocators are informed about this new module's existence. Let's see how memory tags are applied during module loading – that's the key. I anticipate there's a dance between the module loader and the memory management subsystems here. I should be looking for interactions with the allocation tag data structures as I review this code. Let's dig in.
56/3	2026/09/23 23:25	tool	read-file	0m Args: { "File": "mm/alloc_tag.c", "FirstLine": 1100, "LineCount": 40 } Results: { "Contents": "1100:\tstatic int load_module(struct module mod, struct codetag start, struct codetag stop)\n1101:\t{\n1102:\t\t/ Allocate module alloc_tag percpu counters /\n1103:\t\tstruct alloc_tag start_tag;\n1104:\t\tstruct alloc_tag stop_tag;\n1105:\t\tstruct alloc_tag tag;\n1106:\t\n1107:\t\t/* Profiling disabled: load the module without its tags. /\n1108:\t\tif (!mem_profiling_support)\n1109:\t\t\treturn -EOPNOTSUPP;\n1110:\t\n1111:\t\t/ percpu counters for core allocations are already statically allocated /\n1112:\t\tif (!mod)\n1113:\t\t\treturn 0;\n1114:\t\n1115:\t\tstart_tag = ct_to_alloc_tag(start);\n1116:\t\tstop_tag = ct_to_alloc_tag(stop);\n1117:\t\tfor (tag = start_tag; tag \u003c stop_tag; tag++) {\n1118:\t\t\tWARN_ON(tag-\u003ecounters);\n1119:\t\t\ttag-\u003ecounters = alloc_percpu(struct alloc_tag_counters);\n1120:\t\t\tif (!tag-\u003ecounters) {\n1121:\t\t\t\twhile (--tag \u003e= start_tag) {\n1122:\t\t\t\t\tfree_percpu(tag-\u003ecounters);\n1123:\t\t\t\t\ttag-\u003ecounters = NULL;\n1124:\t\t\t\t}\n1125:\t\t\t\tpr_err(\"Failed to allocate memory for allocation tag percpu counters in the module %s\\n\",\n1126:\t\t\t\t mod-\u003ename);\n1127:\t\t\t\treturn -ENOMEM;\n1128:\t\t\t}\n1129:\t\n1130:\t\t\t/\n1131:\t\t\t * Avoid a kmemleak false positive. The pointer to the counters is stored\n1132:\t\t\t * in the alloc_tag section of the module and cannot be directly accessed.\n1133:\t\t\t /\n1134:\t\t\tkmemleak_ignore_percpu(tag-\u003ecounters);\n1135:\t\t}\n1136:\t\treturn 0;\n1137:\t}\n1138:\t\n1139:\tstatic void unload_module(struct module mod, struct codetag start, struct codetag stop)\n" }
57/3	2026/09/23 23:25	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 29869 output: 19 thoughts: 539 Thoughts: Analyzing Concurrency and Tracing in the Module Management Code Okay, so I'm looking at these `load_module` and `unload_module` functions. They both seem to iterate through a range of tags, right? My initial thought is, what about concurrency in `unload_module`? Are there any potential synchronization issues I need to worry about? I immediately zero in on the comment about the read lock `codetag_lock_module_list` and the need for `alloc_tag_trace_mutex` to protect the alloc tag trace toggle. I see that `alloc_tag_trace_mutex` isn't taken in `unload_module`. That raises a red flag. Then I remember that `allocinfo_ioctl_toggle_trace` does take the `codetag_lock_module_list` (as a read lock) when toggling trace. And it also grabs the `alloc_tag_trace_mutex` for the toggle. Aha! But then I see that `unload_module` holds `down_write(&cttype->mod_lock)`. Crucially, because `allocinfo_ioctl_toggle_trace` uses `down_read(&cttype->mod_lock)` within `codetag_lock_module_list`, they can't run concurrently. This eliminates the race I was initially concerned about in that region, because of the read-write lock relationship. So, any potential concurrency issue would be a race/locking issue, and therefore within the domain of KASAN/LOCKDEP, not KMSAN. Good, that's reassuring. Now, I'm shifting my focus to `alloc_tag_add` and `alloc_tag_sub`, particularly when tracing is enabled. I need to be sure that the tracing mechanism is correct. I see the inline functions. The `alloc_tag_trace_enabled(tag)` check is there, and then the trace functions are called. Seems straightforward. But, what is this `ref` variable they're using? What's the context for this `union codetag_ref`? I need to understand this to have a full grasp on tracing. I need to look up how that union is used and how it interacts with the rest of this code. Time to dig into the definition of `union codetag_ref`.
58/3	2026/09/23 23:25	tool	grepper	0m Args: { "Expression": "union codetag_ref" } Results: { "Output": "include/linux/alloc_tag.h=38=struct alloc_tag_module_section {\n--\ninclude/linux/alloc_tag.h-51-\ninclude/linux/alloc_tag.h:52:static inline bool is_codetag_empty(union codetag_ref ref)\ninclude/linux/alloc_tag.h-53-{\n--\ninclude/linux/alloc_tag.h-56-\ninclude/linux/alloc_tag.h:57:static inline void set_codetag_empty(union codetag_ref ref)\ninclude/linux/alloc_tag.h-58-{\n--\ninclude/linux/alloc_tag.h-64-\ninclude/linux/alloc_tag.h:65:static inline bool is_codetag_empty(union codetag_ref ref) { return false; }\ninclude/linux/alloc_tag.h-66-\ninclude/linux/alloc_tag.h:67:static inline void set_codetag_empty(union codetag_ref ref)\ninclude/linux/alloc_tag.h-68-{\n--\ninclude/linux/alloc_tag.h=164=static inline bool alloc_tag_trace_enabled(const struct alloc_tag tag)\n--\ninclude/linux/alloc_tag.h-170-\ninclude/linux/alloc_tag.h:171:void alloc_tag_trace_mem_alloc(union codetag_ref ref, struct alloc_tag tag,\ninclude/linux/alloc_tag.h-172-\t\t\t size_t bytes);\ninclude/linux/alloc_tag.h-173-\ninclude/linux/alloc_tag.h:174:void alloc_tag_trace_mem_free(union codetag_ref ref, struct alloc_tag tag,\ninclude/linux/alloc_tag.h-175-\t\t\t size_t bytes);\n--\ninclude/linux/alloc_tag.h=187=static inline struct alloc_tag_counters alloc_tag_read(struct alloc_tag tag)\n--\ninclude/linux/alloc_tag.h-202-#ifdef CONFIG_MEM_ALLOC_PROFILING_DEBUG\ninclude/linux/alloc_tag.h:203:static inline void alloc_tag_add_check(union codetag_ref ref, struct alloc_tag tag)\ninclude/linux/alloc_tag.h-204-{\n--\ninclude/linux/alloc_tag.h-211-\ninclude/linux/alloc_tag.h:212:static inline void alloc_tag_sub_check(union codetag_ref ref)\ninclude/linux/alloc_tag.h-213-{\n--\ninclude/linux/alloc_tag.h=216=void alloc_tag_add_early_pfn(unsigned long pfn, unsigned int alloc_flags);\ninclude/linux/alloc_tag.h-217-#else\ninclude/linux/alloc_tag.h:218:static inline void alloc_tag_add_check(union codetag_ref ref, struct alloc_tag tag) {}\ninclude/linux/alloc_tag.h:219:static inline void alloc_tag_sub_check(union codetag_ref ref) {}\ninclude/linux/alloc_tag.h-220-static inline void alloc_tag_add_early_pfn(unsigned long pfn, unsigned int alloc_flags) {}\n--\ninclude/linux/alloc_tag.h-223-/* Caller should verify both ref and tag to be valid /\ninclude/linux/alloc_tag.h:224:static inline bool __alloc_tag_ref_set(union codetag_ref ref, struct alloc_tag tag)\ninclude/linux/alloc_tag.h-225-{\n--\ninclude/linux/alloc_tag.h-233-\ninclude/linux/alloc_tag.h:234:static inline bool alloc_tag_ref_set(union codetag_ref ref, struct alloc_tag tag)\ninclude/linux/alloc_tag.h-235-{\n--\ninclude/linux/alloc_tag.h-248-\ninclude/linux/alloc_tag.h:249:static inline void alloc_tag_add(union codetag_ref ref, struct alloc_tag tag, size_t bytes)\ninclude/linux/alloc_tag.h-250-{\n--\ninclude/linux/alloc_tag.h-259-\ninclude/linux/alloc_tag.h:260:static inline void alloc_tag_sub(union codetag_ref ref, size_t bytes)\ninclude/linux/alloc_tag.h-261-{\n--\ninclude/linux/alloc_tag.h=291=static inline bool mem_alloc_profiling_permanently_disabled(void) { return true; }\ninclude/linux/alloc_tag.h:292:static inline void alloc_tag_add(union codetag_ref ref, struct alloc_tag tag,\ninclude/linux/alloc_tag.h-293-\t\t\t\t size_t bytes) {}\ninclude/linux/alloc_tag.h:294:static inline void alloc_tag_sub(union codetag_ref ref, size_t bytes) {}\ninclude/linux/alloc_tag.h-295-static inline void alloc_tag_set_inaccurate(struct alloc_tag tag) {}\n--\ninclude/linux/codetag.h=28=struct codetag {\n--\ninclude/linux/codetag.h-35-\ninclude/linux/codetag.h:36:union codetag_ref {\ninclude/linux/codetag.h-37-\tstruct codetag ct;\n--\ninclude/linux/pgalloc_tag.h=23=union pgtag_ref_handle {\ninclude/linux/pgalloc_tag.h:24:\tunion codetag_ref ref;\t/* reference in page extension /\ninclude/linux/pgalloc_tag.h-25-\tstruct page page;\t/* reference in page flags /\n--\ninclude/linux/pgalloc_tag.h=55=static inline pgalloc_tag_idx module_tag_to_idx(struct alloc_tag tag)\n--\ninclude/linux/pgalloc_tag.h-62-\ninclude/linux/pgalloc_tag.h:63:static inline void idx_to_ref(pgalloc_tag_idx idx, union codetag_ref ref)\ninclude/linux/pgalloc_tag.h-64-{\n--\ninclude/linux/pgalloc_tag.h-80-\ninclude/linux/pgalloc_tag.h:81:static inline pgalloc_tag_idx ref_to_idx(union codetag_ref ref)\ninclude/linux/pgalloc_tag.h-82-{\n--\ninclude/linux/pgalloc_tag.h-100-/* Should be called only if mem_alloc_profiling_enabled() /\ninclude/linux/pgalloc_tag.h:101:static inline bool get_page_tag_ref(struct page page, union codetag_ref ref,\ninclude/linux/pgalloc_tag.h-102-\t\t\t\t union pgtag_ref_handle handle)\n--\ninclude/linux/pgalloc_tag.h-115-\t\tstruct page_ext page_ext;\ninclude/linux/pgalloc_tag.h:116:\t\tunion codetag_ref tmp;\ninclude/linux/pgalloc_tag.h-117-\n--\ninclude/linux/pgalloc_tag.h-121-\ninclude/linux/pgalloc_tag.h:122:\t\ttmp = (union codetag_ref )page_ext_data(page_ext, \u0026page_alloc_tagging_ops);\ninclude/linux/pgalloc_tag.h-123-\t\tref-\u003ect = tmp-\u003ect;\n--\ninclude/linux/pgalloc_tag.h=130=static inline void put_page_tag_ref(union pgtag_ref_handle handle)\n--\ninclude/linux/pgalloc_tag.h-138-\ninclude/linux/pgalloc_tag.h:139:static inline void update_page_tag_ref(union pgtag_ref_handle handle, union codetag_ref ref)\ninclude/linux/pgalloc_tag.h-140-{\n--\ninclude/linux/pgalloc_tag.h=176=static inline struct alloc_tag __pgalloc_tag_get(struct page page)\n--\ninclude/linux/pgalloc_tag.h-179-\tunion pgtag_ref_handle handle;\ninclude/linux/pgalloc_tag.h:180:\tunion codetag_ref ref;\ninclude/linux/pgalloc_tag.h-181-\n--\ninclude/trace/events/alloc_tag.h=63=TRACE_EVENT(alloc_tag_mem_alloced,\ninclude/trace/events/alloc_tag.h-64-\ninclude/trace/events/alloc_tag.h:65:\tTP_PROTO(union codetag_ref ref, struct alloc_tag tag, size_t bytes),\ninclude/trace/events/alloc_tag.h-66-\n--\ninclude/trace/events/alloc_tag.h-69-\tTP_STRUCT__entry(\ninclude/trace/events/alloc_tag.h:70:\t\t__field(union codetag_ref , ref)\ninclude/trace/events/alloc_tag.h-71-\t\t__field(struct alloc_tag , tag)\n--\ninclude/trace/events/alloc_tag.h=94=TRACE_EVENT(alloc_tag_mem_freed,\ninclude/trace/events/alloc_tag.h-95-\ninclude/trace/events/alloc_tag.h:96:\tTP_PROTO(union codetag_ref ref, struct alloc_tag tag, size_t bytes),\ninclude/trace/events/alloc_tag.h-97-\n--\ninclude/trace/events/alloc_tag.h-100-\tTP_STRUCT__entry(\ninclude/trace/events/alloc_tag.h:101:\t\t__field(union codetag_ref , ref)\ninclude/trace/events/alloc_tag.h-102-\t\t__field(struct alloc_tag , tag)\n--\nmm/alloc_tag.c=593=EXPORT_SYMBOL(__alloc_tag_trace_hit);\nmm/alloc_tag.c-594-\nmm/alloc_tag.c:595:void alloc_tag_trace_mem_alloc(union codetag_ref ref, struct alloc_tag tag,\nmm/alloc_tag.c-596-\t\t\t size_t bytes)\n--\nmm/alloc_tag.c=600=EXPORT_SYMBOL(alloc_tag_trace_mem_alloc);\nmm/alloc_tag.c-601-\nmm/alloc_tag.c:602:void alloc_tag_trace_mem_free(union codetag_ref ref, struct alloc_tag tag,\nmm/alloc_tag.c-603-\t\t\t size_t bytes)\n--\nmm/alloc_tag.c=650=void pgalloc_tag_split(struct folio folio, int old_order, int new_order)\n--\nmm/alloc_tag.c-664-\t\tunion pgtag_ref_handle handle;\nmm/alloc_tag.c:665:\t\tunion codetag_ref ref;\nmm/alloc_tag.c-666-\n--\nmm/alloc_tag.c=676=void pgalloc_tag_swap(struct folio new, struct folio old)\n--\nmm/alloc_tag.c-678-\tunion pgtag_ref_handle handle_old, handle_new;\nmm/alloc_tag.c:679:\tunion codetag_ref ref_old, ref_new;\nmm/alloc_tag.c-680-\tstruct alloc_tag tag_old, tag_new;\n--\nmm/alloc_tag.c=1351=static void __init clear_early_alloc_pfn_tag_refs(void)\n--\nmm/alloc_tag.c-1371-\t\t\t\tunion pgtag_ref_handle handle;\nmm/alloc_tag.c:1372:\t\t\t\tunion codetag_ref ref;\nmm/alloc_tag.c-1373-\n--\nmm/alloc_tag.c=1414=struct page_ext_operations page_alloc_tagging_ops = {\nmm/alloc_tag.c:1415:\t.size = sizeof(union codetag_ref),\nmm/alloc_tag.c-1416-\t.need = need_page_alloc_tagging,\n--\nmm/page_alloc.c=1221=void __clear_page_tag_ref(struct page page)\n--\nmm/page_alloc.c-1223-\tunion pgtag_ref_handle handle;\nmm/page_alloc.c:1224:\tunion codetag_ref ref;\nmm/page_alloc.c-1225-\n--\nmm/page_alloc.c=1235=void __pgalloc_tag_add(struct page page, struct task_struct task,\n--\nmm/page_alloc.c-1238-\tunion pgtag_ref_handle handle;\nmm/page_alloc.c:1239:\tunion codetag_ref ref;\nmm/page_alloc.c-1240-\n--\nmm/page_alloc.c=1265=void __pgalloc_tag_sub(struct page page, unsigned int nr)\n--\nmm/page_alloc.c-1267-\tunion pgtag_ref_handle handle;\nmm/page_alloc.c:1268:\tunion codetag_ref ref;\nmm/page_alloc.c-1269-\n--\nmm/percpu-internal.h=35=struct pcpuobj_ext {\n--\nmm/percpu-internal.h-39-#ifdef CONFIG_MEM_ALLOC_PROFILING\nmm/percpu-internal.h:40:\tunion codetag_ref\ttag;\nmm/percpu-internal.h-41-#endif\n--\nmm/slab.h=604=struct slabobj_ext {\n--\nmm/slab.h-613-#ifdef CONFIG_MEM_ALLOC_PROFILING\nmm/slab.h:614:\t\tunion codetag_ref _ctref;\nmm/slab.h-615-#endif\n--\nmm/slab.h=807=slab_obj_ext_set_objcg(struct slab slab, struct slabobj_ext obj_ext,\n--\nmm/slab.h-817-#ifdef CONFIG_MEM_ALLOC_PROFILING\nmm/slab.h:818:static inline union codetag_ref \nmm/slab.h-819-slab_obj_ext_codetag_ref(struct slab slab, struct slabobj_ext obj_ext)\n--\nmm/slub.c=2089=static inline void mark_obj_codetag_empty(const void obj)\n--\nmm/slub.c-2100-\t\tstruct slabobj_ext ext;\nmm/slub.c:2101:\t\tunion codetag_ref ref;\nmm/slub.c-2102-\n--\nmm/slub.c=2124=static inline void handle_failed_objexts_alloc(struct slab slab,\n--\nmm/slub.c-2142-\tfor (unsigned int i = 0; i \u003c slab-\u003eobjects; i++) {\nmm/slub.c:2143:\t\tunion codetag_ref ref = slab_obj_ext_codetag_ref(slab, vec);\nmm/slub.c-2144-\n--\nmm/slub.c=2376=__alloc_tagging_slab_alloc_hook(struct kmem_cache s, void object, gfp_t flags,\n--\nmm/slub.c-2399-\tif (obj_exts) {\nmm/slub.c:2400:\t\tunion codetag_ref ref;\nmm/slub.c-2401-\n" }
59/3	2026/09/23 23:25	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 34905 output: 448 thoughts: 1475 Thoughts: KMSAN Applicability Assessment: Alloc Tag Tracing Enhancement Okay, let's break this down. My initial assessment is that `NeedsKMSAN` should be false for this patch, but I need to be absolutely sure. This is an optimization that adds tracing and an Ioctl command to control it. The core principle I'm working from is that KMSAN is a heavy hammer. It's expensive to run and should only be employed when standard tools like KASAN, LOCKDEP, and the UB sanitizers aren't sufficient. My expertise is in evaluating this kind of code and determining the most effective debugging strategy. First, I need to understand the function of the code, which looks like it's managing memory allocation tags, and allowing tracing of allocations and frees based on these tags. The core operations are `alloc_tag_add` and `alloc_tag_sub`, where the `union codetag_ref` is the key. The code tracks byte counts and call counts associated with these tags. The main change introduces a `trace_on` flag and a toggle command to control it. The `union codetag_ref` itself isn't directly modified but is used to pass arguments to the trace functions. Now, let's step through the KMSAN checklist meticulously: 1. Kernel Structures to User Space: The code modifies `struct allocinfo_counter` by adding `trace_on`. This struct is sent to user space via the `_ALLOCINFO_IOC_GET_AT` and `_ALLOCINFO_IOC_GET_NEXT` ioctls. Critically, these ioctls are always initialized with either `{0}` or `memset()`, zeroing the entire structure, including padding, before copying any data into the user space structure. Furthermore, the `trace_on` field is explicitly set. The new ioctl for tracing control, `ALLOCINFO_IOC_TOGGLE_TRACE`, only receives data from user space and doesn't transmit anything back. There is no risk of uninitialized memory being leaked. 2. Conditional Logic & Uninitialized Variables: The code uses static keys and atomic operations for the tracing flag and related state. These are initialized properly. There are no branches or conditionals that rely on uninitialized values. The atomic flags are initialized. 3. Complex Data Structure Initialization: Codetags, the core of this system, are statically initialized or initialized during module load. No complex data structures are used. 4. Bounds Checks/Uninitialized Byte Access: The code doesn't introduce any new buffer operations or logic that could lead to reading uninitialized bytes from existing buffers. The focus is on accounting and tracing, not direct memory manipulation of the user space buffers. I'm double-checking for other, less obvious, potential risks. Concurrency and locking are always concerns, but the code uses a mutex (`alloc_tag_trace_mutex`) for the new tracing logic and static branches in the main code. The module unload path is handled. I see potential NULL pointer dereference in the trace conditions (`tag && alloc_tag_is_traced(tag)`), but those are easily caught by KASAN or LOCKDEP. Based on this comprehensive review, I'm confident that this patch does not introduce any risk of uninitialized memory usage or info leaks that would only be detectable by KMSAN. All risks are covered by existing sanitizers. Therefore, I'm setting `NeedsKMSAN=false`. My analysis emphasizes the critical distinction between what KASAN, LOCKDEP, and standard tools catch, and what truly warrants a KMSAN-specific investigation. In this case, standard testing and existing bug detectors are sufficient.
60/3	2026/09/23 23:25	tool	set-results	0m Args: { "KMSANReasoning": "The patch introduces tracepoints and an ioctl interface (`ALLOCINFO_IOC_TOGGLE_TRACE`) for memory allocation profiling (`alloc_tag`), as well as adding a `trace_on` field to `struct allocinfo_counter` in the UAPI header.\n\n1. Kernel-to-user info-leak analysis:\nAlthough `struct allocinfo_counter` has its padding adjusted (`pad[7]` reduced to `trace_on` + `pad[6]`), the kernel structures containing it (`allocinfo_get_at` and `allocinfo_tag_data`) are fully zero-initialized with `= {0}` or `memset` in `allocinfo_ioctl_get_at()` and `allocinfo_ioctl_get_next()` prior to copying to user space. Furthermore, the new field `data-\u003ecounter.trace_on` is explicitly assigned in `allocinfo_to_params()`. The new ioctl `ALLOCINFO_IOC_TOGGLE_TRACE` only reads user input via `copy_from_user()` and does not copy any data back to user space.\n\n2. Uninitialized memory access analysis:\nCodetags are statically initialized via `CODETAG_INIT` (`.flags = ATOMIC_INIT(0)`) or allocated/managed during module load. All flags, static keys, and atomic variables are properly initialized before being read. The new tracepoints (`alloc_tag_hit`, `alloc_tag_mem_alloced`, `alloc_tag_mem_freed`) only record initialized pointer references, sizes, and codetag metadata.\n\n3. KASAN / LOCKDEP applicability:\nAny potential issues introduced by this patch (such as concurrency between module unloading and ioctl trace toggles, static branch updates, or pointer validity) fall strictly within the scope of KASAN, LOCKDEP, and standard kernel bug detectors.\n\nTherefore, there is no risk of uninitialized memory usage or information disclosure, and a dedicated KMSAN fuzzing session is not warranted.", "NeedsKMSAN": false } Results: { "KMSANReasoning": "The patch introduces tracepoints and an ioctl interface (`ALLOCINFO_IOC_TOGGLE_TRACE`) for memory allocation profiling (`alloc_tag`), as well as adding a `trace_on` field to `struct allocinfo_counter` in the UAPI header.\n\n1. Kernel-to-user info-leak analysis:\nAlthough `struct allocinfo_counter` has its padding adjusted (`pad[7]` reduced to `trace_on` + `pad[6]`), the kernel structures containing it (`allocinfo_get_at` and `allocinfo_tag_data`) are fully zero-initialized with `= {0}` or `memset` in `allocinfo_ioctl_get_at()` and `allocinfo_ioctl_get_next()` prior to copying to user space. Furthermore, the new field `data-\u003ecounter.trace_on` is explicitly assigned in `allocinfo_to_params()`. The new ioctl `ALLOCINFO_IOC_TOGGLE_TRACE` only reads user input via `copy_from_user()` and does not copy any data back to user space.\n\n2. Uninitialized memory access analysis:\nCodetags are statically initialized via `CODETAG_INIT` (`.flags = ATOMIC_INIT(0)`) or allocated/managed during module load. All flags, static keys, and atomic variables are properly initialized before being read. The new tracepoints (`alloc_tag_hit`, `alloc_tag_mem_alloced`, `alloc_tag_mem_freed`) only record initialized pointer references, sizes, and codetag metadata.\n\n3. KASAN / LOCKDEP applicability:\nAny potential issues introduced by this patch (such as concurrency between module unloading and ioctl trace toggles, static branch updates, or pointer validity) fall strictly within the scope of KASAN, LOCKDEP, and standard kernel bug detectors.\n\nTherefore, there is no risk of uninitialized memory usage or information disclosure, and a dedicated KMSAN fuzzing session is not warranted.", "NeedsKMSAN": false }

LLM Calls Summary:
Total Calls	Total Tokens	Avg Tokens	Total Duration (Seconds)	Avg Duration (Seconds)

Tool Calls Summary:
Total Calls	Total Duration (Seconds)	Avg Duration (Seconds)