AI Trajectory


Trajectory: (Expand/Collapse All)
Seq Timestamp Type Name Duration
0/0 2026/07/16 19:05 flow patch-triage
0m Args: 
null

Results: 
{
  "EnableConfigs": [
    "BPF_SYSCALL"
  ],
  "FocusSymbols": [
    "apply_range_set_cb",
    "apply_range_clear_cb",
    "arena_map_mem_usage",
    "arena_alloc_pages",
    "arena_free_pages",
    "arena_vm_fault"
  ],
  "Reasoning": "The patch adds memory usage tracking to BPF arenas by maintaining a count of populated pages (`nr_pages`). It modifies the page table callbacks (`apply_range_set_cb`, `apply_range_clear_cb`) to update this counter and exposes it via `arena_map_mem_usage`. It also updates the data structures passed to these callbacks in `arena_alloc_pages`, `arena_free_pages`, and `arena_vm_fault`. These are functional changes to core BPF arena memory management and should be fuzzed to ensure the page counting logic is robust and doesn't introduce races or memory leaks.",
  "WorthFuzzing": true
}
1/1 2026/07/16 19:05 action read-patch-diff
0m Args: 
null

Results: 
{
  "PatchDiff": "commit 6270e5fdb9409828b8c9fe28ccdfdbe3682f5a0e\nAuthor: syz-cluster \u003ctriage@syzkaller.com\u003e\nDate:   Thu Jul 16 19:05:39 2026 +0000\n\n    syz-cluster: applied patch under review\n\ndiff --git a/kernel/bpf/arena.c b/kernel/bpf/arena.c\nindex 80b7b8a6944645..bc346021160401 100644\n--- a/kernel/bpf/arena.c\n+++ b/kernel/bpf/arena.c\n@@ -55,8 +55,10 @@ struct bpf_arena {\n \tstruct vm_struct *kern_vm;\n \tstruct page *scratch_page;\n \tstruct range_tree rt;\n-\t/* protects rt */\n+\t/* protects rt and nr_pages */\n \trqspinlock_t spinlock;\n+\t/* number of pages currently populated in the arena */\n+\tu64 nr_pages;\n \tstruct list_head vma_list;\n \t/* protects vma_list */\n \tstruct mutex lock;\n@@ -143,14 +145,14 @@ static long compute_pgoff(struct bpf_arena *arena, long uaddr)\n }\n \n struct apply_range_data {\n+\tstruct bpf_arena *arena;\n \tstruct page **pages;\n-\tstruct page *scratch_page;\n \tint i;\n };\n \n struct clear_range_data {\n+\tstruct bpf_arena *arena;\n \tstruct llist_head *free_pages;\n-\tstruct page *scratch_page;\n };\n \n static int apply_range_set_cb(pte_t *pte, unsigned long addr, void *data)\n@@ -180,7 +182,7 @@ static int apply_range_set_cb(pte_t *pte, unsigned long addr, void *data)\n \n \t\tif (pte_none(old))\n \t\t\tcontinue;\n-\t\tif (WARN_ON_ONCE(pte_page(old) != d-\u003escratch_page))\n+\t\tif (WARN_ON_ONCE(pte_page(old) != d-\u003earena-\u003escratch_page))\n \t\t\treturn -EBUSY;\n \t\tptep_get_and_clear(\u0026init_mm, addr, pte);\n \t\tflush_tlb_before_set(addr);\n@@ -196,6 +198,7 @@ static int apply_range_set_cb(pte_t *pte, unsigned long addr, void *data)\n \tset_pte_at(\u0026init_mm, addr, pte, pteval);\n #endif\n \td-\u003ei++;\n+\td-\u003earena-\u003enr_pages++;\n \treturn 0;\n }\n \n@@ -227,10 +230,11 @@ static int apply_range_clear_cb(pte_t *pte, unsigned long addr, void *data)\n \t * scratches its PTE. A later bpf_arena_free_pages() over that range walks\n \t * here. Without the skip, scratch_page would be freed.\n \t */\n-\tif (page == d-\u003escratch_page)\n+\tif (page == d-\u003earena-\u003escratch_page)\n \t\treturn 0;\n \n \t__llist_add(\u0026page-\u003epcp_llist, d-\u003efree_pages);\n+\td-\u003earena-\u003enr_pages--;\n \treturn 0;\n }\n \n@@ -413,7 +417,9 @@ static int arena_map_check_btf(struct bpf_map *map, const struct btf *btf,\n \n static u64 arena_map_mem_usage(const struct bpf_map *map)\n {\n-\treturn 0;\n+\tstruct bpf_arena *arena = container_of(map, struct bpf_arena, map);\n+\n+\treturn (u64)READ_ONCE(arena-\u003enr_pages) \u003c\u003c PAGE_SHIFT;\n }\n \n struct vma_list {\n@@ -506,8 +512,7 @@ static vm_fault_t arena_vm_fault(struct vm_fault *vmf)\n \tif (ret)\n \t\tgoto out_sigsegv_memcg;\n \n-\tstruct apply_range_data data = { .pages = \u0026page, .i = 0,\n-\t\t\t\t\t .scratch_page = arena-\u003escratch_page };\n+\tstruct apply_range_data data = { .arena = arena, .pages = \u0026page, .i = 0 };\n \t/* Account into memcg of the process that created bpf_arena */\n \tret = bpf_map_alloc_pages(map, NUMA_NO_NODE, 1, \u0026page);\n \tif (ret) {\n@@ -696,8 +701,8 @@ static long arena_alloc_pages(struct bpf_arena *arena, long uaddr, long page_cnt\n \t\tbpf_map_memcg_exit(old_memcg, new_memcg);\n \t\treturn 0;\n \t}\n+\tdata.arena = arena;\n \tdata.pages = pages;\n-\tdata.scratch_page = arena-\u003escratch_page;\n \n \tif (raw_res_spin_lock_irqsave(\u0026arena-\u003espinlock, flags))\n \t\tgoto out_free_pages;\n@@ -873,8 +878,8 @@ static void arena_free_pages(struct bpf_arena *arena, long uaddr, long page_cnt,\n \trange_tree_set(\u0026arena-\u003ert, pgoff, page_cnt);\n \n \tinit_llist_head(\u0026free_pages);\n+\tcdata.arena = arena;\n \tcdata.free_pages = \u0026free_pages;\n-\tcdata.scratch_page = arena-\u003escratch_page;\n \t/* clear ptes and collect struct pages */\n \tapply_to_existing_page_range(\u0026init_mm, kaddr, page_cnt \u003c\u003c PAGE_SHIFT,\n \t\t\t\t     apply_range_clear_cb, \u0026cdata);\n@@ -981,8 +986,8 @@ static void arena_free_worker(struct work_struct *work)\n \tbpf_map_memcg_enter(\u0026arena-\u003emap, \u0026old_memcg, \u0026new_memcg);\n \n \tinit_llist_head(\u0026free_pages);\n+\tcdata.arena = arena;\n \tcdata.free_pages = \u0026free_pages;\n-\tcdata.scratch_page = arena-\u003escratch_page;\n \tarena_vm_start = bpf_arena_get_kern_vm_start(arena);\n \tuser_vm_start = bpf_arena_get_user_vm_start(arena);\n \ndiff --git a/tools/testing/selftests/bpf/prog_tests/arena_atomics.c b/tools/testing/selftests/bpf/prog_tests/arena_atomics.c\nindex d98577a6babc0e..1ad5d03d07adb2 100644\n--- a/tools/testing/selftests/bpf/prog_tests/arena_atomics.c\n+++ b/tools/testing/selftests/bpf/prog_tests/arena_atomics.c\n@@ -222,7 +222,7 @@ static void test_store_release(struct arena_atomics *skel)\n \t\t  \"store_release64_result\");\n }\n \n-void test_arena_atomics(void)\n+void serial_test_arena_atomics(void)\n {\n \tstruct arena_atomics *skel;\n \tint err;\ndiff --git a/tools/testing/selftests/bpf/prog_tests/arena_direct_value.c b/tools/testing/selftests/bpf/prog_tests/arena_direct_value.c\nindex 4b4adb3f4b71eb..01fcf4965ea43c 100644\n--- a/tools/testing/selftests/bpf/prog_tests/arena_direct_value.c\n+++ b/tools/testing/selftests/bpf/prog_tests/arena_direct_value.c\n@@ -66,7 +66,7 @@ static void test_arena_direct_value_one_past_end(void)\n \tclose(map_fd);\n }\n \n-void test_arena_direct_value(void)\n+void serial_test_arena_direct_value(void)\n {\n \tif (test__start_subtest(\"one_past_end\"))\n \t\ttest_arena_direct_value_one_past_end();\ndiff --git a/tools/testing/selftests/bpf/prog_tests/arena_htab.c b/tools/testing/selftests/bpf/prog_tests/arena_htab.c\nindex d69fd2465f5367..91ccf040298040 100644\n--- a/tools/testing/selftests/bpf/prog_tests/arena_htab.c\n+++ b/tools/testing/selftests/bpf/prog_tests/arena_htab.c\n@@ -81,7 +81,7 @@ static void test_arena_htab_asm(void)\n \tarena_htab_asm__destroy(skel);\n }\n \n-void test_arena_htab(void)\n+void serial_test_arena_htab(void)\n {\n \tif (test__start_subtest(\"arena_htab_llvm\"))\n \t\ttest_arena_htab_llvm();\ndiff --git a/tools/testing/selftests/bpf/prog_tests/arena_list.c b/tools/testing/selftests/bpf/prog_tests/arena_list.c\nindex 4f2866a615ce52..2648e06f53d070 100644\n--- a/tools/testing/selftests/bpf/prog_tests/arena_list.c\n+++ b/tools/testing/selftests/bpf/prog_tests/arena_list.c\n@@ -68,7 +68,7 @@ static void test_arena_list_add_del(int cnt, bool nonsleepable)\n \tarena_list__destroy(skel);\n }\n \n-void test_arena_list(void)\n+void serial_test_arena_list(void)\n {\n \tif (test__start_subtest(\"arena_list_1\"))\n \t\ttest_arena_list_add_del(1, false);\ndiff --git a/tools/testing/selftests/bpf/prog_tests/arena_mem_usage.c b/tools/testing/selftests/bpf/prog_tests/arena_mem_usage.c\nnew file mode 100644\nindex 00000000000000..14c2d1a1d673cf\n--- /dev/null\n+++ b/tools/testing/selftests/bpf/prog_tests/arena_mem_usage.c\n@@ -0,0 +1,122 @@\n+// SPDX-License-Identifier: GPL-2.0\n+\n+#include \u003ctest_progs.h\u003e\n+#include \u003csys/user.h\u003e\n+#ifndef PAGE_SIZE /* on some archs it comes in sys/user.h */\n+#include \u003cunistd.h\u003e\n+#define PAGE_SIZE getpagesize()\n+#endif\n+\n+#include \"arena_mem_usage.skel.h\"\n+\n+/*\n+ * arena_map_mem_usage() is surfaced to user space through the map's\n+ * /proc/\u003cpid\u003e/fdinfo/\u003cfd\u003e \"memlock:\" line (the same value bpftool map show\n+ * prints). Read it directly so the test has no external dependency.\n+ */\n+static long map_memlock(int map_fd)\n+{\n+\tchar path[64], line[128];\n+\tlong memlock = -1;\n+\tFILE *f;\n+\n+\tsnprintf(path, sizeof(path), \"/proc/self/fdinfo/%d\", map_fd);\n+\tf = fopen(path, \"r\");\n+\tif (!ASSERT_OK_PTR(f, \"open_fdinfo\"))\n+\t\treturn -1;\n+\twhile (fgets(line, sizeof(line), f)) {\n+\t\tif (sscanf(line, \"memlock:\\t%ld\", \u0026memlock) == 1)\n+\t\t\tbreak;\n+\t}\n+\tfclose(f);\n+\tASSERT_NEQ(memlock, -1, \"parse_memlock\");\n+\treturn memlock;\n+}\n+\n+static int run(struct bpf_program *prog, const char *name)\n+{\n+\tLIBBPF_OPTS(bpf_test_run_opts, opts);\n+\tint err = bpf_prog_test_run_opts(bpf_program__fd(prog), \u0026opts);\n+\n+\tif (!ASSERT_OK(err, name))\n+\t\treturn -1;\n+\tif (!ASSERT_OK(opts.retval, name))\n+\t\treturn -1;\n+\treturn 0;\n+}\n+\n+void serial_test_arena_mem_usage(void)\n+{\n+\tstruct arena_mem_usage *skel;\n+\tconst long ps = PAGE_SIZE;\n+\tchar *base;\n+\tsize_t sz;\n+\tint fd, i;\n+\n+\tskel = arena_mem_usage__open_and_load();\n+\tif (!ASSERT_OK_PTR(skel, \"open_load\"))\n+\t\treturn;\n+\tfd = bpf_map__fd(skel-\u003emaps.arena);\n+\n+\t/* Fresh arena: no data pages, and the scratch page is not counted. */\n+\tASSERT_EQ(map_memlock(fd), 0, \"initial\");\n+\n+\t/* BPF-side allocation of 17 pages. */\n+\tskel-\u003ebss-\u003ealloc_cnt = 17;\n+\tif (run(skel-\u003eprogs.alloc, \"alloc\"))\n+\t\tgoto out;\n+\t/*\n+\t * A NULL ptr means bpf_arena_alloc_pages() itself failed (e.g. the host\n+\t * is under memory pressure), not a miscount -- flag it distinctly so a\n+\t * red CI run is not mistaken for a counting bug.\n+\t */\n+\tif (!ASSERT_OK_PTR(skel-\u003ebss-\u003eptr, \"arena_alloc_pages\"))\n+\t\tgoto out;\n+\tASSERT_EQ(map_memlock(fd), 17 * ps, \"after_alloc\");\n+\n+\t/* Free a single page (arena_free_pages page_cnt==1 path). */\n+\tskel-\u003ebss-\u003efree_byte_off = 0;\n+\tskel-\u003ebss-\u003efree_cnt = 1;\n+\tif (run(skel-\u003eprogs.free_pages, \"free_one\"))\n+\t\tgoto out;\n+\tASSERT_EQ(map_memlock(fd), 16 * ps, \"after_free_one\");\n+\n+\t/* Free ten pages in one call (bulk path); only the freed pages count. */\n+\tskel-\u003ebss-\u003efree_byte_off = 1 * ps;\n+\tskel-\u003ebss-\u003efree_cnt = 10;\n+\tif (run(skel-\u003eprogs.free_pages, \"free_bulk\"))\n+\t\tgoto out;\n+\tASSERT_EQ(map_memlock(fd), 6 * ps, \"after_free_bulk\");\n+\n+\t/* Free the remaining six -\u003e arena empty again. */\n+\tskel-\u003ebss-\u003efree_byte_off = 11 * ps;\n+\tskel-\u003ebss-\u003efree_cnt = 6;\n+\tif (run(skel-\u003eprogs.free_pages, \"free_rest\"))\n+\t\tgoto out;\n+\tASSERT_EQ(map_memlock(fd), 0, \"after_free_rest\");\n+\n+\t/*\n+\t * User-space fault-in: touching unallocated arena pages allocates them\n+\t * through arena_vm_fault(). libbpf mmap()s the arena at map_extra during\n+\t * load, so bpf_map__initial_value() hands back that base.\n+\t */\n+\tbase = bpf_map__initial_value(skel-\u003emaps.arena, \u0026sz);\n+\tif (!ASSERT_OK_PTR(base, \"arena_base\"))\n+\t\tgoto out;\n+\tfor (i = 0; i \u003c 8; i++)\n+\t\tbase[i * ps] = 1;\n+\tASSERT_EQ(map_memlock(fd), 8 * ps, \"after_faultin\");\n+\n+\t/*\n+\t * Free the faulted-in pages from BPF. They are mapped into the user vma\n+\t * (elevated refcount), so this also exercises the zap path.\n+\t */\n+\tskel-\u003ebss-\u003eptr = base;\n+\tskel-\u003ebss-\u003efree_byte_off = 0;\n+\tskel-\u003ebss-\u003efree_cnt = 8;\n+\tif (run(skel-\u003eprogs.free_pages, \"free_faulted\"))\n+\t\tgoto out;\n+\tASSERT_EQ(map_memlock(fd), 0, \"after_free_faulted\");\n+out:\n+\tarena_mem_usage__destroy(skel);\n+}\ndiff --git a/tools/testing/selftests/bpf/prog_tests/arena_spin_lock.c b/tools/testing/selftests/bpf/prog_tests/arena_spin_lock.c\nindex acb9d53b59733f..545b05d7a0aa72 100644\n--- a/tools/testing/selftests/bpf/prog_tests/arena_spin_lock.c\n+++ b/tools/testing/selftests/bpf/prog_tests/arena_spin_lock.c\n@@ -101,7 +101,7 @@ static void test_arena_spin_lock_size(int size)\n \treturn;\n }\n \n-void test_arena_spin_lock(void)\n+void serial_test_arena_spin_lock(void)\n {\n \trepeat = 1000;\n \tif (test__start_subtest(\"arena_spin_lock_1\"))\ndiff --git a/tools/testing/selftests/bpf/prog_tests/arena_strsearch.c b/tools/testing/selftests/bpf/prog_tests/arena_strsearch.c\nindex f81a0c06650596..0c1c6cbfa0f19d 100644\n--- a/tools/testing/selftests/bpf/prog_tests/arena_strsearch.c\n+++ b/tools/testing/selftests/bpf/prog_tests/arena_strsearch.c\n@@ -23,7 +23,7 @@ static void test_arena_str(void)\n \tarena_strsearch__destroy(skel);\n }\n \n-void test_arena_strsearch(void)\n+void serial_test_arena_strsearch(void)\n {\n \tif (test__start_subtest(\"arena_strsearch\"))\n \t\ttest_arena_str();\ndiff --git a/tools/testing/selftests/bpf/prog_tests/libarena.c b/tools/testing/selftests/bpf/prog_tests/libarena.c\nindex ba5a5a50f7c07d..df7e4b8dc39456 100644\n--- a/tools/testing/selftests/bpf/prog_tests/libarena.c\n+++ b/tools/testing/selftests/bpf/prog_tests/libarena.c\n@@ -202,7 +202,7 @@ static void run_libarena_parallel_test(struct libarena *skel, struct bpf_program\n \trun_libarena_parallel_fini(skel, name, prefixlen);\n }\n \n-void test_libarena(void)\n+void serial_test_libarena(void)\n {\n \tstruct arena_alloc_reserve_args args;\n \tstruct libarena *skel;\ndiff --git a/tools/testing/selftests/bpf/prog_tests/libarena_asan.c b/tools/testing/selftests/bpf/prog_tests/libarena_asan.c\nindex f897405f701dd5..9c31b17dbf391f 100644\n--- a/tools/testing/selftests/bpf/prog_tests/libarena_asan.c\n+++ b/tools/testing/selftests/bpf/prog_tests/libarena_asan.c\n@@ -85,7 +85,7 @@ static void run_test(void)\n  * Run the test depending on whether LLVM can compile arena ASAN\n  * programs.\n  */\n-void test_libarena_asan(void)\n+void serial_test_libarena_asan(void)\n {\n #ifdef HAS_BPF_ARENA_ASAN\n \trun_test();\ndiff --git a/tools/testing/selftests/bpf/progs/arena_mem_usage.c b/tools/testing/selftests/bpf/progs/arena_mem_usage.c\nnew file mode 100644\nindex 00000000000000..50d9d6ac86f6b3\n--- /dev/null\n+++ b/tools/testing/selftests/bpf/progs/arena_mem_usage.c\n@@ -0,0 +1,39 @@\n+// SPDX-License-Identifier: GPL-2.0\n+\n+#include \u003cvmlinux.h\u003e\n+#include \u003cbpf/bpf_helpers.h\u003e\n+#include \"bpf_arena_common.h\"\n+\n+struct {\n+\t__uint(type, BPF_MAP_TYPE_ARENA);\n+\t__uint(map_flags, BPF_F_MMAPABLE);\n+\t__uint(max_entries, 1000); /* number of pages */\n+#ifdef __TARGET_ARCH_arm64\n+\t__ulong(map_extra, 0x1ull \u003c\u003c 32); /* start of mmap() region */\n+#else\n+\t__ulong(map_extra, 0x1ull \u003c\u003c 44); /* start of mmap() region */\n+#endif\n+} arena SEC(\".maps\");\n+\n+void __arena *ptr;\n+int alloc_cnt;\t\t/* in:  pages to allocate */\n+long free_byte_off;\t/* in:  byte offset within ptr to start freeing */\n+int free_cnt;\t\t/* in:  pages to free */\n+\n+SEC(\"syscall\")\n+int alloc(void *ctx)\n+{\n+\tptr = bpf_arena_alloc_pages(\u0026arena, NULL, alloc_cnt, NUMA_NO_NODE, 0);\n+\treturn ptr ? 0 : 1;\n+}\n+\n+SEC(\"syscall\")\n+int free_pages(void *ctx)\n+{\n+\tif (!ptr)\n+\t\treturn 1;\n+\tbpf_arena_free_pages(\u0026arena, (char __arena *)ptr + free_byte_off, free_cnt);\n+\treturn 0;\n+}\n+\n+char _license[] SEC(\"license\") = \"GPL\";\n"
}
2/1 2026/07/16 19:05 agent patch-evaluator
0m Model: 
gemini-3.1-pro-preview

Args: 
null

Results: 
{
  "EnableConfigs": [
    "BPF_SYSCALL"
  ],
  "FocusSymbols": [
    "apply_range_set_cb",
    "apply_range_clear_cb",
    "arena_map_mem_usage",
    "arena_alloc_pages",
    "arena_free_pages",
    "arena_vm_fault"
  ],
  "Reasoning": "The patch adds memory usage tracking to BPF arenas by maintaining a count of populated pages (`nr_pages`). It modifies the page table callbacks (`apply_range_set_cb`, `apply_range_clear_cb`) to update this counter and exposes it via `arena_map_mem_usage`. It also updates the data structures passed to these callbacks in `arena_alloc_pages`, `arena_free_pages`, and `arena_vm_fault`. These are functional changes to core BPF arena memory management and should be fuzzed to ensure the page counting logic is robust and doesn't introduce races or memory leaks.",
  "WorthFuzzing": true
}

Instruction: 
You are an expert Linux kernel maintainer.
Your job is to review a provided patch series and determine
if it makes functional changes to the kernel that should be fuzzed.

IMPORTANT: The changes have ALREADY been applied and committed as the HEAD commit in
your workspace. Do NOT rely on your internal knowledge of the kernel. You must actively
use your code access tools to examine the actual source code and confirm any assumptions.

Return WorthFuzzing=false if the patch only contains:
- Modifications to Documentation/, Kconfig files, or code comments.
- Purely decorative changes, such as logging (e.g., pr_err, printk) or tracepoints.
- Changes to numeric constants or macros that do not functionally alter execution flow.
- Code paths that are impossible to reach in virtualized environments like GCE or QEMU,
even when utilizing software-emulated hardware (e.g., usb gadget, mac80211_hwsim).

If it modifies reachable core kernel logic, drivers, or architectures, use your code search
tools to verify the code can be executed, then return WorthFuzzing=true.

When returning WorthFuzzing=true, you MUST ALSO:
1. Extract any specific kernel functions that should be heavily fuzzed into FocusSymbols.
   Avoid listing generic hot-path functions to prevent skewed test distributions.
2. Identify any specific CONFIG_ options required to properly test this new/modified feature.
   Go and look into the Kconfig files and check for ifdefs around the code, do not make assumptions.
   Do not list too generic configs (we already have them enabled). Only list those that
   specifically cover the modified code. List them in the EnableConfigs output array,
   and DO NOT add a '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: 
For your convenience, here is the diff of the changes:
commit 6270e5fdb9409828b8c9fe28ccdfdbe3682f5a0e
Author: syz-cluster <triage@syzkaller.com>
Date:   Thu Jul 16 19:05:39 2026 +0000

    syz-cluster: applied patch under review

diff --git a/kernel/bpf/arena.c b/kernel/bpf/arena.c
index 80b7b8a6944645..bc346021160401 100644
--- a/kernel/bpf/arena.c
+++ b/kernel/bpf/arena.c
@@ -55,8 +55,10 @@ struct bpf_arena {
 	struct vm_struct *kern_vm;
 	struct page *scratch_page;
 	struct range_tree rt;
-	/* protects rt */
+	/* protects rt and nr_pages */
 	rqspinlock_t spinlock;
+	/* number of pages currently populated in the arena */
+	u64 nr_pages;
 	struct list_head vma_list;
 	/* protects vma_list */
 	struct mutex lock;
@@ -143,14 +145,14 @@ static long compute_pgoff(struct bpf_arena *arena, long uaddr)
 }
 
 struct apply_range_data {
+	struct bpf_arena *arena;
 	struct page **pages;
-	struct page *scratch_page;
 	int i;
 };
 
 struct clear_range_data {
+	struct bpf_arena *arena;
 	struct llist_head *free_pages;
-	struct page *scratch_page;
 };
 
 static int apply_range_set_cb(pte_t *pte, unsigned long addr, void *data)
@@ -180,7 +182,7 @@ static int apply_range_set_cb(pte_t *pte, unsigned long addr, void *data)
 
 		if (pte_none(old))
 			continue;
-		if (WARN_ON_ONCE(pte_page(old) != d->scratch_page))
+		if (WARN_ON_ONCE(pte_page(old) != d->arena->scratch_page))
 			return -EBUSY;
 		ptep_get_and_clear(&init_mm, addr, pte);
 		flush_tlb_before_set(addr);
@@ -196,6 +198,7 @@ static int apply_range_set_cb(pte_t *pte, unsigned long addr, void *data)
 	set_pte_at(&init_mm, addr, pte, pteval);
 #endif
 	d->i++;
+	d->arena->nr_pages++;
 	return 0;
 }
 
@@ -227,10 +230,11 @@ static int apply_range_clear_cb(pte_t *pte, unsigned long addr, void *data)
 	 * scratches its PTE. A later bpf_arena_free_pages() over that range walks
 	 * here. Without the skip, scratch_page would be freed.
 	 */
-	if (page == d->scratch_page)
+	if (page == d->arena->scratch_page)
 		return 0;
 
 	__llist_add(&page->pcp_llist, d->free_pages);
+	d->arena->nr_pages--;
 	return 0;
 }
 
@@ -413,7 +417,9 @@ static int arena_map_check_btf(struct bpf_map *map, const struct btf *btf,
 
 static u64 arena_map_mem_usage(const struct bpf_map *map)
 {
-	return 0;
+	struct bpf_arena *arena = container_of(map, struct bpf_arena, map);
+
+	return (u64)READ_ONCE(arena->nr_pages) << PAGE_SHIFT;
 }
 
 struct vma_list {
@@ -506,8 +512,7 @@ static vm_fault_t arena_vm_fault(struct vm_fault *vmf)
 	if (ret)
 		goto out_sigsegv_memcg;
 
-	struct apply_range_data data = { .pages = &page, .i = 0,
-					 .scratch_page = arena->scratch_page };
+	struct apply_range_data data = { .arena = arena, .pages = &page, .i = 0 };
 	/* Account into memcg of the process that created bpf_arena */
 	ret = bpf_map_alloc_pages(map, NUMA_NO_NODE, 1, &page);
 	if (ret) {
@@ -696,8 +701,8 @@ static long arena_alloc_pages(struct bpf_arena *arena, long uaddr, long page_cnt
 		bpf_map_memcg_exit(old_memcg, new_memcg);
 		return 0;
 	}
+	data.arena = arena;
 	data.pages = pages;
-	data.scratch_page = arena->scratch_page;
 
 	if (raw_res_spin_lock_irqsave(&arena->spinlock, flags))
 		goto out_free_pages;
@@ -873,8 +878,8 @@ static void arena_free_pages(struct bpf_arena *arena, long uaddr, long page_cnt,
 	range_tree_set(&arena->rt, pgoff, page_cnt);
 
 	init_llist_head(&free_pages);
+	cdata.arena = arena;
 	cdata.free_pages = &free_pages;
-	cdata.scratch_page = arena->scratch_page;
 	/* clear ptes and collect struct pages */
 	apply_to_existing_page_range(&init_mm, kaddr, page_cnt << PAGE_SHIFT,
 				     apply_range_clear_cb, &cdata);
@@ -981,8 +986,8 @@ static void arena_free_worker(struct work_struct *work)
 	bpf_map_memcg_enter(&arena->map, &old_memcg, &new_memcg);
 
 	init_llist_head(&free_pages);
+	cdata.arena = arena;
 	cdata.free_pages = &free_pages;
-	cdata.scratch_page = arena->scratch_page;
 	arena_vm_start = bpf_arena_get_kern_vm_start(arena);
 	user_vm_start = bpf_arena_get_user_vm_start(arena);
 
diff --git a/tools/testing/selftests/bpf/prog_tests/arena_atomics.c b/tools/testing/selftests/bpf/prog_tests/arena_atomics.c
index d98577a6babc0e..1ad5d03d07adb2 100644
--- a/tools/testing/selftests/bpf/prog_tests/arena_atomics.c
+++ b/tools/testing/selftests/bpf/prog_tests/arena_atomics.c
@@ -222,7 +222,7 @@ static void test_store_release(struct arena_atomics *skel)
 		  "store_release64_result");
 }
 
-void test_arena_atomics(void)
+void serial_test_arena_atomics(void)
 {
 	struct arena_atomics *skel;
 	int err;
diff --git a/tools/testing/selftests/bpf/prog_tests/arena_direct_value.c b/tools/testing/selftests/bpf/prog_tests/arena_direct_value.c
index 4b4adb3f4b71eb..01fcf4965ea43c 100644
--- a/tools/testing/selftests/bpf/prog_tests/arena_direct_value.c
+++ b/tools/testing/selftests/bpf/prog_tests/arena_direct_value.c
@@ -66,7 +66,7 @@ static void test_arena_direct_value_one_past_end(void)
 	close(map_fd);
 }
 
-void test_arena_direct_value(void)
+void serial_test_arena_direct_value(void)
 {
 	if (test__start_subtest("one_past_end"))
 		test_arena_direct_value_one_past_end();
diff --git a/tools/testing/selftests/bpf/prog_tests/arena_htab.c b/tools/testing/selftests/bpf/prog_tests/arena_htab.c
index d69fd2465f5367..91ccf040298040 100644
--- a/tools/testing/selftests/bpf/prog_tests/arena_htab.c
+++ b/tools/testing/selftests/bpf/prog_tests/arena_htab.c
@@ -81,7 +81,7 @@ static void test_arena_htab_asm(void)
 	arena_htab_asm__destroy(skel);
 }
 
-void test_arena_htab(void)
+void serial_test_arena_htab(void)
 {
 	if (test__start_subtest("arena_htab_llvm"))
 		test_arena_htab_llvm();
diff --git a/tools/testing/selftests/bpf/prog_tests/arena_list.c b/tools/testing/selftests/bpf/prog_tests/arena_list.c
index 4f2866a615ce52..2648e06f53d070 100644
--- a/tools/testing/selftests/bpf/prog_tests/arena_list.c
+++ b/tools/testing/selftests/bpf/prog_tests/arena_list.c
@@ -68,7 +68,7 @@ static void test_arena_list_add_del(int cnt, bool nonsleepable)
 	arena_list__destroy(skel);
 }
 
-void test_arena_list(void)
+void serial_test_arena_list(void)
 {
 	if (test__start_subtest("arena_list_1"))
 		test_arena_list_add_del(1, false);
diff --git a/tools/testing/selftests/bpf/prog_tests/arena_mem_usage.c b/tools/testing/selftests/bpf/prog_tests/arena_mem_usage.c
new file mode 100644
index 00000000000000..14c2d1a1d673cf
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/arena_mem_usage.c
@@ -0,0 +1,122 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <test_progs.h>
+#include <sys/user.h>
+#ifndef PAGE_SIZE /* on some archs it comes in sys/user.h */
+#include <unistd.h>
+#define PAGE_SIZE getpagesize()
+#endif
+
+#include "arena_mem_usage.skel.h"
+
+/*
+ * arena_map_mem_usage() is surfaced to user space through the map's
+ * /proc/<pid>/fdinfo/<fd> "memlock:" line (the same value bpftool map show
+ * prints). Read it directly so the test has no external dependency.
+ */
+static long map_memlock(int map_fd)
+{
+	char path[64], line[128];
+	long memlock = -1;
+	FILE *f;
+
+	snprintf(path, sizeof(path), "/proc/self/fdinfo/%d", map_fd);
+	f = fopen(path, "r");
+	if (!ASSERT_OK_PTR(f, "open_fdinfo"))
+		return -1;
+	while (fgets(line, sizeof(line), f)) {
+		if (sscanf(line, "memlock:\t%ld", &memlock) == 1)
+			break;
+	}
+	fclose(f);
+	ASSERT_NEQ(memlock, -1, "parse_memlock");
+	return memlock;
+}
+
+static int run(struct bpf_program *prog, const char *name)
+{
+	LIBBPF_OPTS(bpf_test_run_opts, opts);
+	int err = bpf_prog_test_run_opts(bpf_program__fd(prog), &opts);
+
+	if (!ASSERT_OK(err, name))
+		return -1;
+	if (!ASSERT_OK(opts.retval, name))
+		return -1;
+	return 0;
+}
+
+void serial_test_arena_mem_usage(void)
+{
+	struct arena_mem_usage *skel;
+	const long ps = PAGE_SIZE;
+	char *base;
+	size_t sz;
+	int fd, i;
+
+	skel = arena_mem_usage__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "open_load"))
+		return;
+	fd = bpf_map__fd(skel->maps.arena);
+
+	/* Fresh arena: no data pages, and the scratch page is not counted. */
+	ASSERT_EQ(map_memlock(fd), 0, "initial");
+
+	/* BPF-side allocation of 17 pages. */
+	skel->bss->alloc_cnt = 17;
+	if (run(skel->progs.alloc, "alloc"))
+		goto out;
+	/*
+	 * A NULL ptr means bpf_arena_alloc_pages() itself failed (e.g. the host
+	 * is under memory pressure), not a miscount -- flag it distinctly so a
+	 * red CI run is not mistaken for a counting bug.
+	 */
+	if (!ASSERT_OK_PTR(skel->bss->ptr, "arena_alloc_pages"))
+		goto out;
+	ASSERT_EQ(map_memlock(fd), 17 * ps, "after_alloc");
+
+	/* Free a single page (arena_free_pages page_cnt==1 path). */
+	skel->bss->free_byte_off = 0;
+	skel->bss->free_cnt = 1;
+	if (run(skel->progs.free_pages, "free_one"))
+		goto out;
+	ASSERT_EQ(map_memlock(fd), 16 * ps, "after_free_one");
+
+	/* Free ten pages in one call (bulk path); only the freed pages count. */
+	skel->bss->free_byte_off = 1 * ps;
+	skel->bss->free_cnt = 10;
+	if (run(skel->progs.free_pages, "free_bulk"))
+		goto out;
+	ASSERT_EQ(map_memlock(fd), 6 * ps, "after_free_bulk");
+
+	/* Free the remaining six -> arena empty again. */
+	skel->bss->free_byte_off = 11 * ps;
+	skel->bss->free_cnt = 6;
+	if (run(skel->progs.free_pages, "free_rest"))
+		goto out;
+	ASSERT_EQ(map_memlock(fd), 0, "after_free_rest");
+
+	/*
+	 * User-space fault-in: touching unallocated arena pages allocates them
+	 * through arena_vm_fault(). libbpf mmap()s the arena at map_extra during
+	 * load, so bpf_map__initial_value() hands back that base.
+	 */
+	base = bpf_map__initial_value(skel->maps.arena, &sz);
+	if (!ASSERT_OK_PTR(base, "arena_base"))
+		goto out;
+	for (i = 0; i < 8; i++)
+		base[i * ps] = 1;
+	ASSERT_EQ(map_memlock(fd), 8 * ps, "after_faultin");
+
+	/*
+	 * Free the faulted-in pages from BPF. They are mapped into the user vma
+	 * (elevated refcount), so this also exercises the zap path.
+	 */
+	skel->bss->ptr = base;
+	skel->bss->free_byte_off = 0;
+	skel->bss->free_cnt = 8;
+	if (run(skel->progs.free_pages, "free_faulted"))
+		goto out;
+	ASSERT_EQ(map_memlock(fd), 0, "after_free_faulted");
+out:
+	arena_mem_usage__destroy(skel);
+}
diff --git a/tools/testing/selftests/bpf/prog_tests/arena_spin_lock.c b/tools/testing/selftests/bpf/prog_tests/arena_spin_lock.c
index acb9d53b59733f..545b05d7a0aa72 100644
--- a/tools/testing/selftests/bpf/prog_tests/arena_spin_lock.c
+++ b/tools/testing/selftests/bpf/prog_tests/arena_spin_lock.c
@@ -101,7 +101,7 @@ static void test_arena_spin_lock_size(int size)
 	return;
 }
 
-void test_arena_spin_lock(void)
+void serial_test_arena_spin_lock(void)
 {
 	repeat = 1000;
 	if (test__start_subtest("arena_spin_lock_1"))
diff --git a/tools/testing/selftests/bpf/prog_tests/arena_strsearch.c b/tools/testing/selftests/bpf/prog_tests/arena_strsearch.c
index f81a0c06650596..0c1c6cbfa0f19d 100644
--- a/tools/testing/selftests/bpf/prog_tests/arena_strsearch.c
+++ b/tools/testing/selftests/bpf/prog_tests/arena_strsearch.c
@@ -23,7 +23,7 @@ static void test_arena_str(void)
 	arena_strsearch__destroy(skel);
 }
 
-void test_arena_strsearch(void)
+void serial_test_arena_strsearch(void)
 {
 	if (test__start_subtest("arena_strsearch"))
 		test_arena_str();
diff --git a/tools/testing/selftests/bpf/prog_tests/libarena.c b/tools/testing/selftests/bpf/prog_tests/libarena.c
index ba5a5a50f7c07d..df7e4b8dc39456 100644
--- a/tools/testing/selftests/bpf/prog_tests/libarena.c
+++ b/tools/testing/selftests/bpf/prog_tests/libarena.c
@@ -202,7 +202,7 @@ static void run_libarena_parallel_test(struct libarena *skel, struct bpf_program
 	run_libarena_parallel_fini(skel, name, prefixlen);
 }
 
-void test_libarena(void)
+void serial_test_libarena(void)
 {
 	struct arena_alloc_reserve_args args;
 	struct libarena *skel;
diff --git a/tools/testing/selftests/bpf/prog_tests/libarena_asan.c b/tools/testing/selftests/bpf/prog_tests/libarena_asan.c
index f897405f701dd5..9c31b17dbf391f 100644
--- a/tools/testing/selftests/bpf/prog_tests/libarena_asan.c
+++ b/tools/testing/selftests/bpf/prog_tests/libarena_asan.c
@@ -85,7 +85,7 @@ static void run_test(void)
  * Run the test depending on whether LLVM can compile arena ASAN
  * programs.
  */
-void test_libarena_asan(void)
+void serial_test_libarena_asan(void)
 {
 #ifdef HAS_BPF_ARENA_ASAN
 	run_test();
diff --git a/tools/testing/selftests/bpf/progs/arena_mem_usage.c b/tools/testing/selftests/bpf/progs/arena_mem_usage.c
new file mode 100644
index 00000000000000..50d9d6ac86f6b3
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/arena_mem_usage.c
@@ -0,0 +1,39 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <vmlinux.h>
+#include <bpf/bpf_helpers.h>
+#include "bpf_arena_common.h"
+
+struct {
+	__uint(type, BPF_MAP_TYPE_ARENA);
+	__uint(map_flags, BPF_F_MMAPABLE);
+	__uint(max_entries, 1000); /* number of pages */
+#ifdef __TARGET_ARCH_arm64
+	__ulong(map_extra, 0x1ull << 32); /* start of mmap() region */
+#else
+	__ulong(map_extra, 0x1ull << 44); /* start of mmap() region */
+#endif
+} arena SEC(".maps");
+
+void __arena *ptr;
+int alloc_cnt;		/* in:  pages to allocate */
+long free_byte_off;	/* in:  byte offset within ptr to start freeing */
+int free_cnt;		/* in:  pages to free */
+
+SEC("syscall")
+int alloc(void *ctx)
+{
+	ptr = bpf_arena_alloc_pages(&arena, NULL, alloc_cnt, NUMA_NO_NODE, 0);
+	return ptr ? 0 : 1;
+}
+
+SEC("syscall")
+int free_pages(void *ctx)
+{
+	if (!ptr)
+		return 1;
+	bpf_arena_free_pages(&arena, (char __arena *)ptr + free_byte_off, free_cnt);
+	return 0;
+}
+
+char _license[] SEC("license") = "GPL";

3/2 2026/07/16 19:05 llm patch-evaluator
0m Model: 
gemini-3.1-pro-preview

Args: 
null

Results: 
null

Tokens: 
							input: 7313
							output: 35
							thoughts: 300

Thoughts: 
**Analyzing the BPF Arena Patch for Fuzzing Potential**

Okay, so I've got this patch affecting `kernel/bpf/arena.c` and introducing a new test, `tools/testing/selftests/bpf/prog_tests/arena_mem_usage.c`. My initial thought is to assess its fuzzing potential – is this something worth sinking time into?

The core of the patch revolves around memory usage tracking within the BPF arena. Specifically, it's adding `nr_pages` to the `struct bpf_arena` to keep tabs on the number of pages currently in use. Makes sense, that's a crucial piece of information for any memory management scheme. I see modifications to callbacks like `apply_range_set_cb` (incrementing `nr_pages`), `apply_range_clear_cb` (decrementing it), and the `arena_map_mem_usage` function. The `arena_map_mem_usage` change is just grabbing that page count and shifting it appropriately. The code also appears to be refactoring some structs to pass `arena` rather than just the `scratch_page`.

So, the question is, *is this code reachable and vulnerable to something like a memory corruption?* Given my experience with BPF, the answer is a likely yes. It modifies the arena logic, and the arena itself is accessible through `BPF_MAP_TYPE_ARENA` operations. The functions being touched – `apply_range_set_cb`, `apply_range_clear_cb`, `arena_map_mem_usage`, `arena_vm_fault`, `arena_alloc_pages`, `arena_free_pages`, and `arena_free_worker` – are all prime targets. These are critical functions involved in managing the arena’s state, including allocating and freeing pages and handling memory access. A miscalculation here could lead to some very interesting memory issues. I should pull up `kernel/bpf/arena.c` and dig in. It's time to find a way to break it!

4/2 2026/07/16 19:05 tool grepper
0m Args: 
{
  "Expression": "arena_map_mem_usage",
  "PathPrefix": "kernel/bpf/arena.c"
}

Results: 
{
  "Output": "kernel/bpf/arena.c=412=static int arena_map_check_btf(struct bpf_map *map, const struct btf *btf,\n--\nkernel/bpf/arena.c-417-\nkernel/bpf/arena.c:418:static u64 arena_map_mem_usage(const struct bpf_map *map)\nkernel/bpf/arena.c-419-{\n--\nkernel/bpf/arena.c=636=const struct bpf_map_ops arena_map_ops = {\n--\nkernel/bpf/arena.c-650-\t.map_check_btf = arena_map_check_btf,\nkernel/bpf/arena.c:651:\t.map_mem_usage = arena_map_mem_usage,\nkernel/bpf/arena.c-652-\t.map_btf_id = \u0026bpf_arena_map_btf_ids[0],\n"
}
5/2 2026/07/16 19:05 llm patch-evaluator
0m Model: 
gemini-3.1-pro-preview

Args: 
null

Results: 
null

Tokens: 
							input: 8340
							output: 35
							thoughts: 100

Thoughts: 
**Analyzing Memory Usage in Arena Maps**

Okay, let's break this down. My understanding is that the `arena_map_mem_usage` variable plays a role within the `arena_map_ops` structure. This is the core of memory management. I need to trace how the memory usage data is manipulated.

Specifically, `nr_pages` is the target variable here. I see that it's getting updated within the `apply_range_set_cb` and `apply_range_clear_cb` callback functions. Interesting. Those callbacks, in turn, are being passed to the `apply_to_existing_page_range` and `apply_to_page_range` functions. It looks like they're the workhorses applying changes over a range of memory pages.

Now, to solidify my comprehension, I need to zoom in on what the `apply_range_set_cb` and `apply_range_clear_cb` functions are actually doing. Let's delve into their implementation to get a clearer picture of the page management logic and how they're contributing to the `arena_map_mem_usage` figure. I'm especially interested in the intricacies of how they change `nr_pages` in their respective set and clear operations.

6/2 2026/07/16 19:05 tool grepper
0m Args: 
{
  "Expression": "apply_range_set_cb",
  "PathPrefix": "kernel/bpf/arena.c"
}

Results: 
{
  "Output": "kernel/bpf/arena.c=153=struct clear_range_data {\n--\nkernel/bpf/arena.c-157-\nkernel/bpf/arena.c:158:static int apply_range_set_cb(pte_t *pte, unsigned long addr, void *data)\nkernel/bpf/arena.c-159-{\n--\nkernel/bpf/arena.c=259=static int populate_pgtable_except_pte(struct bpf_arena *arena)\n--\nkernel/bpf/arena.c-262-\treturn apply_to_page_range(\u0026init_mm, bpf_arena_get_kern_vm_start(arena),\nkernel/bpf/arena.c:263:\t\t\t\t   SZ_4G + GUARD_SZ / 2, apply_range_set_cb, NULL);\nkernel/bpf/arena.c-264-}\n--\nkernel/bpf/arena.c=479=static vm_fault_t arena_vm_fault(struct vm_fault *vmf)\n--\nkernel/bpf/arena.c-522-\nkernel/bpf/arena.c:523:\tret = apply_to_page_range(\u0026init_mm, kaddr, PAGE_SIZE, apply_range_set_cb, \u0026data);\nkernel/bpf/arena.c-524-\tif (ret) {\n--\nkernel/bpf/arena.c=664=static long arena_alloc_pages(struct bpf_arena *arena, long uaddr, long page_cnt, int node_id,\n--\nkernel/bpf/arena.c-746-\t\t\t\t\t  kern_vm_start + uaddr32 + (mapped \u003c\u003c PAGE_SHIFT),\nkernel/bpf/arena.c:747:\t\t\t\t\t  this_batch \u003c\u003c PAGE_SHIFT, apply_range_set_cb, \u0026data);\nkernel/bpf/arena.c-748-\t\tif (ret) {\n"
}
7/2 2026/07/16 19:05 llm patch-evaluator
0m Model: 
gemini-3.1-pro-preview

Args: 
null

Results: 
null

Tokens: 
							input: 9233
							output: 25
							thoughts: 268

Thoughts: 
**BPF Arena Memory Tracking: A Closer Look**

Okay, so this patch introduces memory usage tracking for BPF arenas, which is a sensible addition. It seems pretty straightforward on the surface, updating `nr_pages` and returning it via `arena_map_mem_usage`. This is functional, but the main goal is memory tracking. I don't see anything overly complex at first glance.

The code changes are mostly about refactoring: replacing `scratch_page` with `arena` in a couple of functions, `apply_range_data` and `clear_range_data`. It increments `nr_pages` within `apply_range_set_cb` and decrements it within `apply_range_clear_cb`. Nothing too crazy, but this touches core BPF arena memory management.

Given that this modifies arena memory management, fuzzing is definitely warranted. It's a good target. I should focus my attention on these symbols: `apply_range_set_cb`, `apply_range_clear_cb`, `arena_map_mem_usage`, `arena_alloc_pages`, and `arena_free_pages`. Oh, and `arena_vm_fault` might also be relevant.

Wait, are those callback functions, `apply_range_set_cb` and `apply_range_clear_cb`, static? Okay, I need to verify whether these static callbacks are reachable during BPF arena operations and if I can effectively target them with fuzzing.

Good, they *are* called during BPF arena operations. Excellent.

Now, let me just quickly check the Kconfig for anything relevant to BPF arena configurations.

8/2 2026/07/16 19:06 tool grepper
0m Args: 
{
  "Expression": "BPF_ARENA",
  "PathPrefix": ""
}

Results: 
{
  "Output": "arch/arm64/net/bpf_jit_comp.c=1046=static void build_epilogue(struct jit_ctx *ctx, bool was_classic)\n--\narch/arm64/net/bpf_jit_comp.c-1100-#define BPF_FIXUP_ARENA_REG_MASK   GENMASK(20, 16)\narch/arm64/net/bpf_jit_comp.c:1101:#define BPF_ARENA_ACCESS           BIT(21)\narch/arm64/net/bpf_jit_comp.c-1102-#define BPF_FIXUP_REG_MASK\tGENMASK(31, 27)\n--\narch/arm64/net/bpf_jit_comp.c=1105=bool ex_handler_bpf(const struct exception_table_entry *ex,\n--\narch/arm64/net/bpf_jit_comp.c-1110-\tint arena_reg = FIELD_GET(BPF_FIXUP_ARENA_REG_MASK, ex-\u003efixup);\narch/arm64/net/bpf_jit_comp.c:1111:\tbool is_arena = !!(ex-\u003efixup \u0026 BPF_ARENA_ACCESS);\narch/arm64/net/bpf_jit_comp.c-1112-\tbool is_write = (dst_reg == DONT_CLEAR);\n--\narch/arm64/net/bpf_jit_comp.c=1129=static int add_exception_handler(const struct bpf_insn *insn,\n--\narch/arm64/net/bpf_jit_comp.c-1186-\tif (is_arena) {\narch/arm64/net/bpf_jit_comp.c:1187:\t\tex-\u003efixup |= BPF_ARENA_ACCESS;\narch/arm64/net/bpf_jit_comp.c-1188-\t\t/*\n--\ntools/sched_ext/include/scx/bpf_arena_common.bpf.h-16-\ntools/sched_ext/include/scx/bpf_arena_common.bpf.h:17:#if defined(__BPF_FEATURE_ADDR_SPACE_CAST) \u0026\u0026 !defined(BPF_ARENA_FORCE_ASM)\ntools/sched_ext/include/scx/bpf_arena_common.bpf.h-18-#ifndef __arena\n--\ntools/testing/selftests/bpf/Makefile=844=LIBARENA_ASAN_SKEL := libarena/libarena_asan.skel.h\ntools/testing/selftests/bpf/Makefile:845:CFLAGS += -DHAS_BPF_ARENA_ASAN\ntools/testing/selftests/bpf/Makefile-846-\n--\ntools/testing/selftests/bpf/libarena/Makefile=79=libarena.bpf.o: $(LIBARENA_OBJECTS)\n--\ntools/testing/selftests/bpf/libarena/Makefile-84-\t$(call msg,CLNG-BPF,libarena,$@)\ntools/testing/selftests/bpf/libarena/Makefile:85:\t$(Q)$(CLANG) $(BPF_CFLAGS) $(ASAN_FLAGS) -DBPF_ARENA_ASAN $(BPF_TARGET_ENDIAN) -c $\u003c -o $@\ntools/testing/selftests/bpf/libarena/Makefile-86-\n--\ntools/testing/selftests/bpf/libarena/include/bpf_arena_common.h-34-\ntools/testing/selftests/bpf/libarena/include/bpf_arena_common.h:35:#if defined(__BPF_FEATURE_ADDR_SPACE_CAST) \u0026\u0026 !defined(BPF_ARENA_FORCE_ASM)\ntools/testing/selftests/bpf/libarena/include/bpf_arena_common.h-36-#define __arena __attribute__((address_space(1))) __attribute__((btf_type_tag(\"arena\")))\n--\ntools/testing/selftests/bpf/libarena/include/bpf_arena_spin_lock.h-2-/* Copyright (c) 2025 Meta Platforms, Inc. and affiliates. */\ntools/testing/selftests/bpf/libarena/include/bpf_arena_spin_lock.h:3:#ifndef BPF_ARENA_SPIN_LOCK_H\ntools/testing/selftests/bpf/libarena/include/bpf_arena_spin_lock.h:4:#define BPF_ARENA_SPIN_LOCK_H\ntools/testing/selftests/bpf/libarena/include/bpf_arena_spin_lock.h-5-\n--\ntools/testing/selftests/bpf/libarena/include/bpf_arena_spin_lock.h=516=static __always_inline void arena_spin_unlock(arena_spinlock_t __arena *lock)\n--\ntools/testing/selftests/bpf/libarena/include/bpf_arena_spin_lock.h-542-\ntools/testing/selftests/bpf/libarena/include/bpf_arena_spin_lock.h:543:#endif /* BPF_ARENA_SPIN_LOCK_H */\n--\ntools/testing/selftests/bpf/libarena/include/libarena/asan.h=15=extern volatile bool asan_report_once;\n--\ntools/testing/selftests/bpf/libarena/include/libarena/asan.h-25-\ntools/testing/selftests/bpf/libarena/include/libarena/asan.h:26:#ifdef BPF_ARENA_ASAN\ntools/testing/selftests/bpf/libarena/include/libarena/asan.h-27-\n--\ntools/testing/selftests/bpf/libarena/include/libarena/asan.h=85=static void (*__asan_btf_anchors[])(intptr_t) = {\n--\ntools/testing/selftests/bpf/libarena/include/libarena/asan.h-91-\ntools/testing/selftests/bpf/libarena/include/libarena/asan.h:92:#else /* BPF_ARENA_ASAN */\ntools/testing/selftests/bpf/libarena/include/libarena/asan.h-93-\n--\ntools/testing/selftests/bpf/libarena/include/libarena/asan.h=97=__weak bool asan_ready(void) { return true; }\ntools/testing/selftests/bpf/libarena/include/libarena/asan.h-98-\ntools/testing/selftests/bpf/libarena/include/libarena/asan.h:99:#endif /* BPF_ARENA_ASAN */\ntools/testing/selftests/bpf/libarena/include/libarena/asan.h-100-\n--\ntools/testing/selftests/bpf/libarena/selftests/test_asan_buddy.bpf.c=11=extern struct buddy __arena buddy;\ntools/testing/selftests/bpf/libarena/selftests/test_asan_buddy.bpf.c-12-\ntools/testing/selftests/bpf/libarena/selftests/test_asan_buddy.bpf.c:13:#ifdef BPF_ARENA_ASAN\ntools/testing/selftests/bpf/libarena/selftests/test_asan_buddy.bpf.c-14-\n--\ntools/testing/selftests/bpf/libarena/src/asan.bpf.c=8=enum {\n--\ntools/testing/selftests/bpf/libarena/src/asan.bpf.c-80-\ntools/testing/selftests/bpf/libarena/src/asan.bpf.c:81:#ifdef BPF_ARENA_ASAN\ntools/testing/selftests/bpf/libarena/src/asan.bpf.c-82-\n--\ntools/testing/selftests/bpf/libarena/src/asan.bpf.c=485=__weak __noasan int asan_init(struct asan_init_args *args)\n--\ntools/testing/selftests/bpf/libarena/src/asan.bpf.c-550-\ntools/testing/selftests/bpf/libarena/src/asan.bpf.c:551:#endif /* BPF_ARENA_ASAN */\ntools/testing/selftests/bpf/libarena/src/asan.bpf.c-552-\n--\ntools/testing/selftests/bpf/prog_tests/libarena_asan.c-4-\ntools/testing/selftests/bpf/prog_tests/libarena_asan.c:5:#ifdef HAS_BPF_ARENA_ASAN\ntools/testing/selftests/bpf/prog_tests/libarena_asan.c-6-#include \u003cunistd.h\u003e\n--\ntools/testing/selftests/bpf/prog_tests/libarena_asan.c=37=static void run_test(void)\n--\ntools/testing/selftests/bpf/prog_tests/libarena_asan.c-81-\ntools/testing/selftests/bpf/prog_tests/libarena_asan.c:82:#endif /* HAS_BPF_ARENA_ASAN */\ntools/testing/selftests/bpf/prog_tests/libarena_asan.c-83-\n--\ntools/testing/selftests/bpf/prog_tests/libarena_asan.c=88=void serial_test_libarena_asan(void)\ntools/testing/selftests/bpf/prog_tests/libarena_asan.c-89-{\ntools/testing/selftests/bpf/prog_tests/libarena_asan.c:90:#ifdef HAS_BPF_ARENA_ASAN\ntools/testing/selftests/bpf/prog_tests/libarena_asan.c-91-\trun_test();\n--\ntools/testing/selftests/bpf/progs/arena_htab.c=26=int arena_htab_llvm(void *ctx)\ntools/testing/selftests/bpf/progs/arena_htab.c-27-{\ntools/testing/selftests/bpf/progs/arena_htab.c:28:#if defined(__BPF_FEATURE_ADDR_SPACE_CAST) || defined(BPF_ARENA_FORCE_ASM)\ntools/testing/selftests/bpf/progs/arena_htab.c-29-\tstruct htab __arena *htab;\n--\ntools/testing/selftests/bpf/progs/arena_htab_asm.c-2-/* Copyright (c) 2024 Meta Platforms, Inc. and affiliates. */\ntools/testing/selftests/bpf/progs/arena_htab_asm.c:3:#define BPF_ARENA_FORCE_ASM\ntools/testing/selftests/bpf/progs/arena_htab_asm.c-4-#define arena_htab_llvm arena_htab_asm\n"
}
9/2 2026/07/16 19:06 llm patch-evaluator
0m Model: 
gemini-3.1-pro-preview

Args: 
null

Results: 
null

Tokens: 
							input: 12655
							output: 29
							thoughts: 56

Thoughts: 
**Investigating the BPF Arena Configuration**

Okay, so I'm looking into the `CONFIG_BPF_ARENA` configuration, and it's immediately apparent that it's not a standalone option. It seems to be intertwined with `CONFIG_BPF_SYSCALL`, which is something to keep in mind. I need to understand how the arena functionality is actually being compiled. My next step is to dive into the `kernel/bpf/Makefile`. I need to figure out if `arena.o`—the object file related to the arena—is compiled conditionally based on any specific configuration flags, and if so, what those flags are. That Makefile should provide the key. I need to trace this dependency and ascertain its precise relationship.

10/2 2026/07/16 19:06 tool grepper
0m Args: 
{
  "Expression": "arena.o",
  "PathPrefix": "kernel/bpf/Makefile"
}

Results: 
{
  "Output": "kernel/bpf/Makefile=19=ifeq ($(CONFIG_MMU)$(CONFIG_64BIT),yy)\nkernel/bpf/Makefile:20:obj-$(CONFIG_BPF_SYSCALL) += arena.o range_tree.o\nkernel/bpf/Makefile-21-endif\n"
}
11/2 2026/07/16 19:06 llm patch-evaluator
0m Model: 
gemini-3.1-pro-preview

Args: 
null

Results: 
null

Tokens: 
							input: 12981
							output: 33
							thoughts: 295

Thoughts: 
**My Initial Assessment of the BPF Arena Memory Tracking Patch**

Okay, so I'm looking at this patch and my initial thought is that the primary enabling configuration here is `CONFIG_BPF_SYSCALL`, which makes sense. I see it also requires `CONFIG_MMU` and `CONFIG_64BIT`, which is expected given the nature of BPF. The code is using `BPF_SYSCALL` directly. Makes sense.

The core of the change seems to be within `kernel/bpf/arena.c`, focusing on the BPF arena implementation, specifically the introduction of memory usage tracking. My first thought is to zero in on the key symbols involved. I'm focusing on `apply_range_set_cb`, `apply_range_clear_cb`, `arena_map_mem_usage`, `arena_alloc_pages`, `arena_free_pages`, and `arena_vm_fault`. These seem like the critical functions affected.

Now, a quick follow-up thought... I'm noticing that `apply_range_set_cb` and `apply_range_clear_cb` are static callbacks, so I'm wondering if they're inlined. If they are inlined, that could make them harder for syzkaller to target directly. However, they're passed as function pointers to `apply_to_page_range` and `apply_to_existing_page_range`, so it looks like they won't be inlined. That's good. `arena_map_mem_usage` is a callback within `bpf_map_ops`, so it's probably accessible through the map operations. `arena_alloc_pages` and `arena_free_pages` are called as BPF program helpers, which I like because I can control them from a BPF program. Finally, `arena_vm_fault` is a `vm_operations_struct` callback, so it's tied to virtual memory operations.

Just to be absolutely sure, I'm going to quickly double check that `arena_alloc_pages` is indeed a helper. Gotta be certain about that.

12/2 2026/07/16 19:06 tool grepper
0m Args: 
{
  "Expression": "arena_alloc_pages",
  "PathPrefix": "kernel/bpf/arena.c"
}

Results: 
{
  "Output": "kernel/bpf/arena.c-39- * into kernel and user vma.\nkernel/bpf/arena.c:40: * bpf program can allocate a page via bpf_arena_alloc_pages() kfunc\nkernel/bpf/arena.c-41- * which will insert it into kernel vm_area.\n--\nkernel/bpf/arena.c=655=static u64 clear_lo32(u64 val)\n--\nkernel/bpf/arena.c-663- */\nkernel/bpf/arena.c:664:static long arena_alloc_pages(struct bpf_arena *arena, long uaddr, long page_cnt, int node_id,\nkernel/bpf/arena.c-665-\t\t\t      bool sleepable)\n--\nkernel/bpf/arena.c=843=static void arena_free_pages(struct bpf_arena *arena, long uaddr, long page_cnt, bool sleepable)\n--\nkernel/bpf/arena.c-930- * Reserve an arena virtual address range without populating it. This call stops\nkernel/bpf/arena.c:931: * bpf_arena_alloc_pages from adding pages to this range.\nkernel/bpf/arena.c-932- */\n--\nkernel/bpf/arena.c=1041=__bpf_kfunc_start_defs();\nkernel/bpf/arena.c-1042-\nkernel/bpf/arena.c:1043:__bpf_kfunc void *bpf_arena_alloc_pages(void *p__map, void *addr__ign, u32 page_cnt,\nkernel/bpf/arena.c-1044-\t\t\t\t\tint node_id, u64 flags)\n--\nkernel/bpf/arena.c-1051-\nkernel/bpf/arena.c:1052:\treturn (void *)arena_alloc_pages(arena, (long)addr__ign, page_cnt, node_id, true);\nkernel/bpf/arena.c-1053-}\nkernel/bpf/arena.c-1054-\nkernel/bpf/arena.c:1055:void *bpf_arena_alloc_pages_non_sleepable(void *p__map, void *addr__ign, u32 page_cnt,\nkernel/bpf/arena.c-1056-\t\t\t\t\t  int node_id, u64 flags)\n--\nkernel/bpf/arena.c-1063-\nkernel/bpf/arena.c:1064:\treturn (void *)arena_alloc_pages(arena, (long)addr__ign, page_cnt, node_id, false);\nkernel/bpf/arena.c-1065-}\nkernel/bpf/arena.c-1066-\nkernel/bpf/arena.c:1067:void *bpf_arena_alloc_pages_sleepable(void *p__map, void *addr__ign, u32 page_cnt,\nkernel/bpf/arena.c-1068-\t\t\t\t      int node_id, u64 flags)\n--\nkernel/bpf/arena.c-1075-\nkernel/bpf/arena.c:1076:\treturn (void *)arena_alloc_pages(arena, (long)addr__ign, page_cnt, node_id, true);\nkernel/bpf/arena.c-1077-}\n--\nkernel/bpf/arena.c=1114=BTF_KFUNCS_START(arena_kfuncs)\nkernel/bpf/arena.c:1115:BTF_ID_FLAGS(func, bpf_arena_alloc_pages, KF_ARENA_RET | KF_ARENA_ARG2)\nkernel/bpf/arena.c-1116-BTF_ID_FLAGS(func, bpf_arena_free_pages, KF_ARENA_ARG2)\n"
}
13/2 2026/07/16 19:06 llm patch-evaluator
0m Model: 
gemini-3.1-pro-preview

Args: 
null

Results: 
null

Tokens: 
							input: 14743
							output: 223
							thoughts: 404

Thoughts: 
**Analyzing the BPF Arena Memory Usage Patch**

Okay, so `bpf_arena_alloc_pages` is indeed a kfunc, as expected. This patch looks like it's making some key modifications to how the arena memory is managed. It's changing `arena_alloc_pages` and `arena_free_pages` to pass the `arena` structure instead of `scratch_page` to `apply_range_data` and `clear_range_data`. It also introduces `arena_map_mem_usage`, which is called when you're looking at the file descriptor info for the map. I see a new test, `arena_mem_usage.c`, that's designed to exercise this new functionality. Definitely worth fuzzing to validate these changes.

Let's nail down the critical symbols:

*   `apply_range_set_cb`
*   `apply_range_clear_cb`
*   `arena_map_mem_usage`
*   `arena_alloc_pages`
*   `arena_free_pages`
*   `arena_vm_fault`

Now, regarding the config dependencies... `BPF_SYSCALL` is the main one. I can assume `CONFIG_MMU` and `CONFIG_64BIT` are standard on syzkaller targets (especially x86\_64), so focusing on `BPF_SYSCALL` is sufficient.

Here's my reasoning: This patch is injecting memory usage tracking into BPF arenas. Specifically, it's maintaining a count of populated pages via `nr_pages`. The update involves modifying page table callbacks (`apply_range_set_cb`, `apply_range_clear_cb`) to update this counter. The new `arena_map_mem_usage` function provides a way to expose this usage. Changes also flow through `arena_alloc_pages`, `arena_free_pages`, and `arena_vm_fault`. It's a functional change that alters core arena memory management. Therefore, it absolutely requires fuzzing. We have to ensure that the page counting logic is sound and doesn't introduce any races, leaks, or other memory corruption issues. It's time to call set-results.

14/2 2026/07/16 19:06 tool set-results
0m Args: 
{
  "EnableConfigs": [
    "BPF_SYSCALL"
  ],
  "FocusSymbols": [
    "apply_range_set_cb",
    "apply_range_clear_cb",
    "arena_map_mem_usage",
    "arena_alloc_pages",
    "arena_free_pages",
    "arena_vm_fault"
  ],
  "Reasoning": "The patch adds memory usage tracking to BPF arenas by maintaining a count of populated pages (`nr_pages`). It modifies the page table callbacks (`apply_range_set_cb`, `apply_range_clear_cb`) to update this counter and exposes it via `arena_map_mem_usage`. It also updates the data structures passed to these callbacks in `arena_alloc_pages`, `arena_free_pages`, and `arena_vm_fault`. These are functional changes to core BPF arena memory management and should be fuzzed to ensure the page counting logic is robust and doesn't introduce races or memory leaks.",
  "WorthFuzzing": true
}

Results: 
{
  "EnableConfigs": [
    "BPF_SYSCALL"
  ],
  "FocusSymbols": [
    "apply_range_set_cb",
    "apply_range_clear_cb",
    "arena_map_mem_usage",
    "arena_alloc_pages",
    "arena_free_pages",
    "arena_vm_fault"
  ],
  "Reasoning": "The patch adds memory usage tracking to BPF arenas by maintaining a count of populated pages (`nr_pages`). It modifies the page table callbacks (`apply_range_set_cb`, `apply_range_clear_cb`) to update this counter and exposes it via `arena_map_mem_usage`. It also updates the data structures passed to these callbacks in `arena_alloc_pages`, `arena_free_pages`, and `arena_vm_fault`. These are functional changes to core BPF arena memory management and should be fuzzed to ensure the page counting logic is robust and doesn't introduce races or memory leaks.",
  "WorthFuzzing": true
}
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)