AI Trajectory

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Seq	Timestamp	Type	Name	Duration
0/0	2026/09/18 20:57	flow	patch-triage	1m Args: null Results: { "EnableConfigs": [ "BPF_SYSCALL" ], "FocusSymbols": [ "destroy_dynptrs_on_func_exit", "destroy_if_dynptr_stack_slot", "prepare_func_exit", "process_bpf_exit_full", "mark_stack_slots_dynptr" ], "KMSANReasoning": "The patch modifies the BPF verifier (kernel/bpf/verifier.c) to tear down local dynptrs and invalidate derived slices when returning from a BPF subprogram (prepare_func_exit). It also adds a check ensuring that departing stack frames cannot drop the last dynptr referencing a resource.\n\nFrom a memory safety perspective:\n1. The bug being addressed relates to stale slices and reference tracking across stack frames, which at runtime in BPF programs could lead to use-after-free or dangling pointer dereferences. These memory corruption bugs are caught by standard KASAN, not KMSAN.\n2. The patch touches only static verifier verification state logic and selftests. No kernel-to-userspace copies (info-leaks), uninitialized stack/heap allocations, or branches on uninitialized memory are introduced or exposed. All variables in the new verifier functions are fully initialized.\n\nTherefore, this change does not introduce or expose uninitialized memory risks, and a dedicated KMSAN fuzzing session is not warranted.", "NeedsKMSAN": false, "Reasoning": "The patch modifies core BPF verifier logic in kernel/bpf/verifier.c by adding teardown of callee-local dynptrs on function return (destroy_dynptrs_on_func_exit) called from prepare_func_exit(). It invalidates slices derived from local dynptrs and rejects returns when the last dynptr holding a referenced resource is about to be lost. This is fully reachable from userspace via the bpf() syscall (BPF_PROG_LOAD) and warrants fuzzing for verifier state tracking bugs, pruning regressions, or false verifier rejections/acceptances.", "WorthFuzzing": true }
1/1	2026/09/18 20:57	action	read-patch-diff	0m Args: null Results: { "PatchDiff": "commit d38f515d2bf5529abf4e8907d23dee8c7e4074a4\nAuthor: syz-cluster \u003ctriage@syzkaller.com\u003e\nDate: Fri Sep 18 20:57:25 2026 +0000\n\n syz-cluster: applied patch under review\n\ndiff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c\nindex 6c6b8d8520cdf..4beca102c11d1 100644\n--- a/kernel/bpf/verifier.c\n+++ b/kernel/bpf/verifier.c\n@@ -709,7 +709,8 @@ static void mark_dynptr_cb_reg(struct bpf_verifier_env env,\n }\n \n static int destroy_if_dynptr_stack_slot(struct bpf_verifier_env env,\n-\t\t\t\t struct bpf_func_state state, int spi);\n+\t\t\t\t\tstruct bpf_func_state state, int spi,\n+\t\t\t\t\tbool on_func_exit);\n \n static int mark_stack_slots_dynptr(struct bpf_verifier_env env, struct bpf_reg_state reg,\n \t\t\t\t enum bpf_arg_type arg_type, int insn_idx,\n@@ -732,10 +733,10 @@ static int mark_stack_slots_dynptr(struct bpf_verifier_env env, struct bpf_reg_\n \t case they do belong to same dynptr, second call won't see slot_type\n \t * as STACK_DYNPTR and will simply skip destruction.\n \t /\n-\terr = destroy_if_dynptr_stack_slot(env, state, spi);\n+\terr = destroy_if_dynptr_stack_slot(env, state, spi, false);\n \tif (err)\n \t\treturn err;\n-\terr = destroy_if_dynptr_stack_slot(env, state, spi - 1);\n+\terr = destroy_if_dynptr_stack_slot(env, state, spi - 1, false);\n \tif (err)\n \t\treturn err;\n \n@@ -843,8 +844,34 @@ static int dynptr_ref_cnt(struct bpf_verifier_env env, int v_parent_id)\n \treturn ref_cnt;\n }\n \n+static int destroy_dynptrs_on_func_exit(struct bpf_verifier_env env,\n+\t\t\t\t\tstruct bpf_func_state callee)\n+{\n+\tint i, err;\n+\n+\tfor (i = 0; i \u003c callee-\u003eallocated_stack / BPF_REG_SIZE; i++) {\n+\t\tstruct bpf_stack_state slot = \u0026callee-\u003estack[i];\n+\n+\t\tif (slot-\u003eslot_type[0] != STACK_DYNPTR \|\|\n+\t\t !slot-\u003espilled_ptr.dynptr.first_slot)\n+\t\t\tcontinue;\n+\n+\t\t/\n+\t\t * A callee-local dynptr is destroyed when its stack frame goes\n+\t\t * away. Apply the normal stack-slot teardown so references cannot\n+\t\t * be lost and slices derived from that dynptr are invalidated.\n+\t\t /\n+\t\terr = destroy_if_dynptr_stack_slot(env, callee, i, true);\n+\t\tif (err)\n+\t\t\treturn err;\n+\t}\n+\n+\treturn 0;\n+}\n+\n static int destroy_if_dynptr_stack_slot(struct bpf_verifier_env env,\n-\t\t\t\t struct bpf_func_state state, int spi)\n+\t\t\t\t\tstruct bpf_func_state state, int spi,\n+\t\t\t\t\tbool on_func_exit)\n {\n \tint err = 0;\n \n@@ -867,6 +894,15 @@ static int destroy_if_dynptr_stack_slot(struct bpf_verifier_env env,\n \t /\n \tif (dynptr_type_referenced(state-\u003estack[spi].spilled_ptr.dynptr.type) \u0026\u0026\n \t dynptr_ref_cnt(env, state-\u003estack[spi].spilled_ptr.parent_id) \u003c= 1) {\n+\t\tif (on_func_exit) {\n+\t\t\tverbose(env, \"cannot return with referenced dynptr in callee stack\\n\");\n+\t\t\tbpf_diag_res(env, env-\u003einsn_idx,\n+\t\t\t\t \"referenced dynptr on function return\",\n+\t\t\t\t \"The departing stack frame contains the last dynptr that can release a referenced resource.\",\n+\t\t\t\t \"Release the referenced resource before returning from this function.\");\n+\t\t\treturn -EINVAL;\n+\t\t}\n+\n \t\tverbose(env, \"cannot overwrite referenced dynptr\\n\");\n \t\tbpf_diag_res(\n \t\t\tenv, env-\u003einsn_idx, \"referenced dynptr overwrite\",\n@@ -3630,7 +3666,7 @@ static int check_stack_write_fixed_off(struct bpf_verifier_env env,\n \t\t\tenv-\u003einsn_aux_data[insn_idx].nospec_result = true;\n \t}\n \n-\terr = destroy_if_dynptr_stack_slot(env, state, spi);\n+\terr = destroy_if_dynptr_stack_slot(env, state, spi, false);\n \tif (err)\n \t\treturn err;\n \n@@ -3750,7 +3786,7 @@ static int check_stack_write_var_off(struct bpf_verifier_env env,\n \t\tint spi;\n \n \t\tspi = bpf_get_spi(i);\n-\t\terr = destroy_if_dynptr_stack_slot(env, state, spi);\n+\t\terr = destroy_if_dynptr_stack_slot(env, state, spi, false);\n \t\tif (err)\n \t\t\treturn err;\n \t}\n@@ -11043,6 +11079,9 @@ static int prepare_func_exit(struct bpf_verifier_env env, int insn_idx)\n \t\t\tbpf_diag_mod_end(env);\n \t\t}\n \t}\n+\terr = destroy_dynptrs_on_func_exit(env, callee);\n+\tif (err)\n+\t\treturn err;\n \n \t/* for callbacks like bpf_loop or bpf_for_each_map_elem go back to callsite,\n \t * there function call logic would reschedule callback visit. If iteration\ndiff --git a/tools/testing/selftests/bpf/prog_tests/bpf_qdisc.c b/tools/testing/selftests/bpf/prog_tests/bpf_qdisc.c\nindex 6dbd1487343c0..122ecb7e98e2a 100644\n--- a/tools/testing/selftests/bpf/prog_tests/bpf_qdisc.c\n+++ b/tools/testing/selftests/bpf/prog_tests/bpf_qdisc.c\n@@ -11,6 +11,7 @@\n #include \"bpf_qdisc_fail__invalid_dynptr.skel.h\"\n #include \"bpf_qdisc_fail__invalid_dynptr_slice.skel.h\"\n #include \"bpf_qdisc_fail__invalid_dynptr_cross_frame.skel.h\"\n+#include \"bpf_qdisc_fail__invalid_dynptr_returned_slice.skel.h\"\n #include \"bpf_qdisc_fail__untrusted_write.skel.h\"\n #include \"bpf_qdisc_dynptr_use_after_invalidate_clone.skel.h\"\n \n@@ -230,6 +231,7 @@ void test_ns_bpf_qdisc(void)\n \t\ttest_incompl_ops();\n \tRUN_TESTS(bpf_qdisc_fail__invalid_dynptr);\n \tRUN_TESTS(bpf_qdisc_fail__invalid_dynptr_cross_frame);\n+\tRUN_TESTS(bpf_qdisc_fail__invalid_dynptr_returned_slice);\n \tRUN_TESTS(bpf_qdisc_fail__invalid_dynptr_slice);\n \tRUN_TESTS(bpf_qdisc_fail__untrusted_write);\n \tRUN_TESTS(bpf_qdisc_dynptr_use_after_invalidate_clone);\ndiff --git a/tools/testing/selftests/bpf/progs/bpf_qdisc_fail__invalid_dynptr_returned_slice.c b/tools/testing/selftests/bpf/progs/bpf_qdisc_fail__invalid_dynptr_returned_slice.c\nnew file mode 100644\nindex 0000000000000..8217f4c4c00c4\n--- /dev/null\n+++ b/tools/testing/selftests/bpf/progs/bpf_qdisc_fail__invalid_dynptr_returned_slice.c\n@@ -0,0 +1,76 @@\n+// SPDX-License-Identifier: GPL-2.0\n+\n+#include \u003cvmlinux.h\u003e\n+#include \"bpf_experimental.h\"\n+#include \"bpf_qdisc_common.h\"\n+#include \"bpf_misc.h\"\n+\n+char _license[] SEC(\"license\") = \"GPL\";\n+\n+int proto;\n+\n+static __noinline struct ethhdr slice_in_subprog(struct sk_buff skb)\n+{\n+\tstruct bpf_dynptr ptr;\n+\n+\tbpf_dynptr_from_skb((struct __sk_buff )skb, 0, \u0026ptr);\n+\treturn bpf_dynptr_slice(\u0026ptr, 0, NULL, sizeof(struct ethhdr));\n+}\n+\n+SEC(\"struct_ops\")\n+__failure __msg(\"invalid mem access 'scalar'\")\n+int BPF_PROG(invalid_dynptr_returned_slice, struct sk_buff skb,\n+\t struct Qdisc sch, struct bpf_sk_buff_ptr to_free)\n+{\n+\tstruct ethhdr hdr;\n+\n+\thdr = slice_in_subprog(skb);\n+\tif (!hdr) {\n+\t\tbpf_qdisc_skb_drop(skb, to_free);\n+\t\treturn NET_XMIT_DROP;\n+\t}\n+\n+\t/ this should fail /\n+\tproto = hdr-\u003eh_proto;\n+\n+\tbpf_qdisc_skb_drop(skb, to_free);\n+\n+\treturn NET_XMIT_DROP;\n+}\n+\n+SEC(\"struct_ops\")\n+__auxiliary\n+struct sk_buff BPF_PROG(bpf_qdisc_test_dequeue, struct Qdisc sch)\n+{\n+\treturn NULL;\n+}\n+\n+SEC(\"struct_ops\")\n+__auxiliary\n+int BPF_PROG(bpf_qdisc_test_init, struct Qdisc sch, struct nlattr opt,\n+\t struct netlink_ext_ack extack)\n+{\n+\treturn 0;\n+}\n+\n+SEC(\"struct_ops\")\n+__auxiliary\n+void BPF_PROG(bpf_qdisc_test_reset, struct Qdisc sch)\n+{\n+}\n+\n+SEC(\"struct_ops\")\n+__auxiliary\n+void BPF_PROG(bpf_qdisc_test_destroy, struct Qdisc sch)\n+{\n+}\n+\n+SEC(\".struct_ops\")\n+struct Qdisc_ops test = {\n+\t.enqueue = (void )invalid_dynptr_returned_slice,\n+\t.dequeue = (void )bpf_qdisc_test_dequeue,\n+\t.init = (void )bpf_qdisc_test_init,\n+\t.reset = (void )bpf_qdisc_test_reset,\n+\t.destroy = (void )bpf_qdisc_test_destroy,\n+\t.id = \"bpf_qdisc_test\",\n+};\ndiff --git a/tools/testing/selftests/bpf/progs/dynptr_fail.c b/tools/testing/selftests/bpf/progs/dynptr_fail.c\nindex 1cd61d72c166f..aed18403ae3c0 100644\n--- a/tools/testing/selftests/bpf/progs/dynptr_fail.c\n+++ b/tools/testing/selftests/bpf/progs/dynptr_fail.c\n@@ -125,9 +125,9 @@ static int missing_release_callback_fn(__u32 index, void data)\n \treturn 0;\n }\n \n-/* Any dynptr initialized within a callback must have bpf_dynptr_put called /\n+/ A callback cannot return with the last dynptr for a referenced resource. /\n SEC(\"?raw_tp\")\n-__failure __msg(\"Unreleased reference id\")\n+__failure __msg(\"cannot return with referenced dynptr\")\n int ringbuf_missing_release_callback(void ctx)\n {\n \tbpf_loop(10, missing_release_callback_fn, NULL, 0);\n@@ -1892,6 +1892,101 @@ int clone_invalidate4(void ctx)\n \treturn 0;\n }\n \n+static __noinline void clone_slice_in_subprog(struct bpf_dynptr ptr, int *data)\n+{\n+\tstruct bpf_dynptr clone;\n+\n+\tbpf_dynptr_clone(ptr, \u0026clone);\n+\tdata = bpf_dynptr_data(\u0026clone, 0, sizeof(val));\n+}\n+\n+static __noinline void caller_slice_in_subprog(struct bpf_dynptr ptr, int data)\n+{\n+\tstruct bpf_dynptr clone;\n+\n+\tdata = bpf_dynptr_data(ptr, 0, sizeof(val));\n+\tbpf_dynptr_clone(ptr, \u0026clone);\n+}\n+\n+static __noinline void reserve_dynptr_in_subprog(void)\n+{\n+\tstruct bpf_dynptr ptr;\n+\n+\tbpf_ringbuf_reserve_dynptr(\u0026ringbuf, val, 0, \u0026ptr);\n+}\n+\n+/* A subprogram cannot lose the last dynptr that can release a resource. /\n+SEC(\"?raw_tp\")\n+__failure __msg(\"cannot return with referenced dynptr\")\n+int referenced_dynptr_lost_on_subprog_return(void ctx)\n+{\n+\treserve_dynptr_in_subprog();\n+\n+\treturn 0;\n+}\n+\n+/\n+ Destroying a local clone on return must not invalidate a slice whose\n+ * source dynptr belongs to the caller.\n+ /\n+SEC(\"?raw_tp\")\n+__success\n+int caller_dynptr_slice_across_subprog_valid(void ctx)\n+{\n+\tstruct bpf_dynptr ptr;\n+\tint data = NULL;\n+\n+\tbpf_ringbuf_reserve_dynptr(\u0026ringbuf, val, 0, \u0026ptr);\n+\tcaller_slice_in_subprog(\u0026ptr, \u0026data);\n+\tif (data)\n+\t\tdata = 123;\n+\tbpf_ringbuf_submit_dynptr(\u0026ptr, 0);\n+\n+\treturn 0;\n+}\n+\n+/\n+ A slice that escapes a clone's call frame is invalid once the local\n+ * clone is destroyed on return.\n+ /\n+SEC(\"?raw_tp\")\n+__failure __msg(\"invalid mem access 'scalar'\")\n+int clone_slice_returned_frame_invalid(void ctx)\n+{\n+\tstruct bpf_dynptr ptr;\n+\tint data = NULL;\n+\n+\tbpf_ringbuf_reserve_dynptr(\u0026ringbuf, val, 0, \u0026ptr);\n+\tclone_slice_in_subprog(\u0026ptr, \u0026data);\n+\tif (data)\n+\t\t/ this should fail /\n+\t\tdata = 123;\n+\tbpf_ringbuf_submit_dynptr(\u0026ptr, 0);\n+\n+\treturn 0;\n+}\n+\n+/\n+ A slice from a caller-owned dynptr survives the subprogram return, but\n+ * releasing the shared reservation must invalidate it.\n+ /\n+SEC(\"?raw_tp\")\n+__failure __msg(\"invalid mem access 'scalar'\")\n+int caller_dynptr_slice_release_after_subprog_invalid(void ctx)\n+{\n+\tstruct bpf_dynptr ptr;\n+\tint data = NULL;\n+\n+\tbpf_ringbuf_reserve_dynptr(\u0026ringbuf, val, 0, \u0026ptr);\n+\tcaller_slice_in_subprog(\u0026ptr, \u0026data);\n+\tbpf_ringbuf_submit_dynptr(\u0026ptr, 0);\n+\tif (data)\n+\t\t/ this should fail /\n+\t\tdata = 123;\n+\n+\treturn 0;\n+}\n+\n /* Invalidating a dynptr should invalidate any data slices\n * of its parent\n */\n" }
2/1	2026/09/18 20:57	agent	patch-evaluator	0m Model: core Args: null Results: { "EnableConfigs": [ "BPF_SYSCALL" ], "FocusSymbols": [ "destroy_dynptrs_on_func_exit", "destroy_if_dynptr_stack_slot", "prepare_func_exit", "process_bpf_exit_full", "mark_stack_slots_dynptr" ], "Reasoning": "The patch modifies core BPF verifier logic in kernel/bpf/verifier.c by adding teardown of callee-local dynptrs on function return (destroy_dynptrs_on_func_exit) called from prepare_func_exit(). It invalidates slices derived from local dynptrs and rejects returns when the last dynptr holding a referenced resource is about to be lost. This is fully reachable from userspace via the bpf() syscall (BPF_PROG_LOAD) and warrants fuzzing for verifier state tracking bugs, pruning regressions, or false verifier rejections/acceptances.", "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 d38f515d2bf5529abf4e8907d23dee8c7e4074a4 Author: syz-cluster <triage@syzkaller.com> Date: Fri Sep 18 20:57:25 2026 +0000 syz-cluster: applied patch under review diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 6c6b8d8520cdf..4beca102c11d1 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -709,7 +709,8 @@ static void mark_dynptr_cb_reg(struct bpf_verifier_env env, } static int destroy_if_dynptr_stack_slot(struct bpf_verifier_env env, - struct bpf_func_state state, int spi); + struct bpf_func_state state, int spi, + bool on_func_exit); static int mark_stack_slots_dynptr(struct bpf_verifier_env env, struct bpf_reg_state reg, enum bpf_arg_type arg_type, int insn_idx, @@ -732,10 +733,10 @@ static int mark_stack_slots_dynptr(struct bpf_verifier_env env, struct bpf_reg_ case they do belong to same dynptr, second call won't see slot_type * as STACK_DYNPTR and will simply skip destruction. / - err = destroy_if_dynptr_stack_slot(env, state, spi); + err = destroy_if_dynptr_stack_slot(env, state, spi, false); if (err) return err; - err = destroy_if_dynptr_stack_slot(env, state, spi - 1); + err = destroy_if_dynptr_stack_slot(env, state, spi - 1, false); if (err) return err; @@ -843,8 +844,34 @@ static int dynptr_ref_cnt(struct bpf_verifier_env env, int v_parent_id) return ref_cnt; } +static int destroy_dynptrs_on_func_exit(struct bpf_verifier_env env, + struct bpf_func_state callee) +{ + int i, err; + + for (i = 0; i < callee->allocated_stack / BPF_REG_SIZE; i++) { + struct bpf_stack_state slot = &callee->stack[i]; + + if (slot->slot_type[0] != STACK_DYNPTR \|\| + !slot->spilled_ptr.dynptr.first_slot) + continue; + + / + * A callee-local dynptr is destroyed when its stack frame goes + * away. Apply the normal stack-slot teardown so references cannot + * be lost and slices derived from that dynptr are invalidated. + / + err = destroy_if_dynptr_stack_slot(env, callee, i, true); + if (err) + return err; + } + + return 0; +} + static int destroy_if_dynptr_stack_slot(struct bpf_verifier_env env, - struct bpf_func_state state, int spi) + struct bpf_func_state state, int spi, + bool on_func_exit) { int err = 0; @@ -867,6 +894,15 @@ static int destroy_if_dynptr_stack_slot(struct bpf_verifier_env env, / if (dynptr_type_referenced(state->stack[spi].spilled_ptr.dynptr.type) && dynptr_ref_cnt(env, state->stack[spi].spilled_ptr.parent_id) <= 1) { + if (on_func_exit) { + verbose(env, "cannot return with referenced dynptr in callee stack\n"); + bpf_diag_res(env, env->insn_idx, + "referenced dynptr on function return", + "The departing stack frame contains the last dynptr that can release a referenced resource.", + "Release the referenced resource before returning from this function."); + return -EINVAL; + } + verbose(env, "cannot overwrite referenced dynptr\n"); bpf_diag_res( env, env->insn_idx, "referenced dynptr overwrite", @@ -3630,7 +3666,7 @@ static int check_stack_write_fixed_off(struct bpf_verifier_env env, env->insn_aux_data[insn_idx].nospec_result = true; } - err = destroy_if_dynptr_stack_slot(env, state, spi); + err = destroy_if_dynptr_stack_slot(env, state, spi, false); if (err) return err; @@ -3750,7 +3786,7 @@ static int check_stack_write_var_off(struct bpf_verifier_env env, int spi; spi = bpf_get_spi(i); - err = destroy_if_dynptr_stack_slot(env, state, spi); + err = destroy_if_dynptr_stack_slot(env, state, spi, false); if (err) return err; } @@ -11043,6 +11079,9 @@ static int prepare_func_exit(struct bpf_verifier_env env, int insn_idx) bpf_diag_mod_end(env); } } + err = destroy_dynptrs_on_func_exit(env, callee); + if (err) + return err; /* for callbacks like bpf_loop or bpf_for_each_map_elem go back to callsite, * there function call logic would reschedule callback visit. If iteration diff --git a/tools/testing/selftests/bpf/prog_tests/bpf_qdisc.c b/tools/testing/selftests/bpf/prog_tests/bpf_qdisc.c index 6dbd1487343c0..122ecb7e98e2a 100644 --- a/tools/testing/selftests/bpf/prog_tests/bpf_qdisc.c +++ b/tools/testing/selftests/bpf/prog_tests/bpf_qdisc.c @@ -11,6 +11,7 @@ #include "bpf_qdisc_fail__invalid_dynptr.skel.h" #include "bpf_qdisc_fail__invalid_dynptr_slice.skel.h" #include "bpf_qdisc_fail__invalid_dynptr_cross_frame.skel.h" +#include "bpf_qdisc_fail__invalid_dynptr_returned_slice.skel.h" #include "bpf_qdisc_fail__untrusted_write.skel.h" #include "bpf_qdisc_dynptr_use_after_invalidate_clone.skel.h" @@ -230,6 +231,7 @@ void test_ns_bpf_qdisc(void) test_incompl_ops(); RUN_TESTS(bpf_qdisc_fail__invalid_dynptr); RUN_TESTS(bpf_qdisc_fail__invalid_dynptr_cross_frame); + RUN_TESTS(bpf_qdisc_fail__invalid_dynptr_returned_slice); RUN_TESTS(bpf_qdisc_fail__invalid_dynptr_slice); RUN_TESTS(bpf_qdisc_fail__untrusted_write); RUN_TESTS(bpf_qdisc_dynptr_use_after_invalidate_clone); diff --git a/tools/testing/selftests/bpf/progs/bpf_qdisc_fail__invalid_dynptr_returned_slice.c b/tools/testing/selftests/bpf/progs/bpf_qdisc_fail__invalid_dynptr_returned_slice.c new file mode 100644 index 0000000000000..8217f4c4c00c4 --- /dev/null +++ b/tools/testing/selftests/bpf/progs/bpf_qdisc_fail__invalid_dynptr_returned_slice.c @@ -0,0 +1,76 @@ +// SPDX-License-Identifier: GPL-2.0 + +#include <vmlinux.h> +#include "bpf_experimental.h" +#include "bpf_qdisc_common.h" +#include "bpf_misc.h" + +char _license[] SEC("license") = "GPL"; + +int proto; + +static __noinline struct ethhdr slice_in_subprog(struct sk_buff skb) +{ + struct bpf_dynptr ptr; + + bpf_dynptr_from_skb((struct __sk_buff )skb, 0, &ptr); + return bpf_dynptr_slice(&ptr, 0, NULL, sizeof(struct ethhdr)); +} + +SEC("struct_ops") +__failure __msg("invalid mem access 'scalar'") +int BPF_PROG(invalid_dynptr_returned_slice, struct sk_buff skb, + struct Qdisc sch, struct bpf_sk_buff_ptr to_free) +{ + struct ethhdr hdr; + + hdr = slice_in_subprog(skb); + if (!hdr) { + bpf_qdisc_skb_drop(skb, to_free); + return NET_XMIT_DROP; + } + + / this should fail / + proto = hdr->h_proto; + + bpf_qdisc_skb_drop(skb, to_free); + + return NET_XMIT_DROP; +} + +SEC("struct_ops") +__auxiliary +struct sk_buff BPF_PROG(bpf_qdisc_test_dequeue, struct Qdisc sch) +{ + return NULL; +} + +SEC("struct_ops") +__auxiliary +int BPF_PROG(bpf_qdisc_test_init, struct Qdisc sch, struct nlattr opt, + struct netlink_ext_ack extack) +{ + return 0; +} + +SEC("struct_ops") +__auxiliary +void BPF_PROG(bpf_qdisc_test_reset, struct Qdisc sch) +{ +} + +SEC("struct_ops") +__auxiliary +void BPF_PROG(bpf_qdisc_test_destroy, struct Qdisc sch) +{ +} + +SEC(".struct_ops") +struct Qdisc_ops test = { + .enqueue = (void )invalid_dynptr_returned_slice, + .dequeue = (void )bpf_qdisc_test_dequeue, + .init = (void )bpf_qdisc_test_init, + .reset = (void )bpf_qdisc_test_reset, + .destroy = (void )bpf_qdisc_test_destroy, + .id = "bpf_qdisc_test", +}; diff --git a/tools/testing/selftests/bpf/progs/dynptr_fail.c b/tools/testing/selftests/bpf/progs/dynptr_fail.c index 1cd61d72c166f..aed18403ae3c0 100644 --- a/tools/testing/selftests/bpf/progs/dynptr_fail.c +++ b/tools/testing/selftests/bpf/progs/dynptr_fail.c @@ -125,9 +125,9 @@ static int missing_release_callback_fn(__u32 index, void data) return 0; } -/* Any dynptr initialized within a callback must have bpf_dynptr_put called / +/ A callback cannot return with the last dynptr for a referenced resource. / SEC("?raw_tp") -__failure __msg("Unreleased reference id") +__failure __msg("cannot return with referenced dynptr") int ringbuf_missing_release_callback(void ctx) { bpf_loop(10, missing_release_callback_fn, NULL, 0); @@ -1892,6 +1892,101 @@ int clone_invalidate4(void ctx) return 0; } +static __noinline void clone_slice_in_subprog(struct bpf_dynptr ptr, int *data) +{ + struct bpf_dynptr clone; + + bpf_dynptr_clone(ptr, &clone); + data = bpf_dynptr_data(&clone, 0, sizeof(val)); +} + +static __noinline void caller_slice_in_subprog(struct bpf_dynptr ptr, int data) +{ + struct bpf_dynptr clone; + + data = bpf_dynptr_data(ptr, 0, sizeof(val)); + bpf_dynptr_clone(ptr, &clone); +} + +static __noinline void reserve_dynptr_in_subprog(void) +{ + struct bpf_dynptr ptr; + + bpf_ringbuf_reserve_dynptr(&ringbuf, val, 0, &ptr); +} + +/* A subprogram cannot lose the last dynptr that can release a resource. / +SEC("?raw_tp") +__failure __msg("cannot return with referenced dynptr") +int referenced_dynptr_lost_on_subprog_return(void ctx) +{ + reserve_dynptr_in_subprog(); + + return 0; +} + +/* + * Destroying a local clone on return must not invalidate a slice whose + * source dynptr belongs to the caller. + / +SEC("?raw_tp") +__success +int caller_dynptr_slice_across_subprog_valid(void ctx) +{ + struct bpf_dynptr ptr; + int data = NULL; + + bpf_ringbuf_reserve_dynptr(&ringbuf, val, 0, &ptr); + caller_slice_in_subprog(&ptr, &data); + if (data) + data = 123; + bpf_ringbuf_submit_dynptr(&ptr, 0); + + return 0; +} + +/* + * A slice that escapes a clone's call frame is invalid once the local + * clone is destroyed on return. + / +SEC("?raw_tp") +__failure __msg("invalid mem access 'scalar'") +int clone_slice_returned_frame_invalid(void ctx) +{ + struct bpf_dynptr ptr; + int data = NULL; + + bpf_ringbuf_reserve_dynptr(&ringbuf, val, 0, &ptr); + clone_slice_in_subprog(&ptr, &data); + if (data) + / this should fail / + data = 123; + bpf_ringbuf_submit_dynptr(&ptr, 0); + + return 0; +} + +/* + * A slice from a caller-owned dynptr survives the subprogram return, but + * releasing the shared reservation must invalidate it. + / +SEC("?raw_tp") +__failure __msg("invalid mem access 'scalar'") +int caller_dynptr_slice_release_after_subprog_invalid(void ctx) +{ + struct bpf_dynptr ptr; + int data = NULL; + + bpf_ringbuf_reserve_dynptr(&ringbuf, val, 0, &ptr); + caller_slice_in_subprog(&ptr, &data); + bpf_ringbuf_submit_dynptr(&ptr, 0); + if (data) + / this should fail / + data = 123; + + return 0; +} + /* Invalidating a dynptr should invalidate any data slices * of its parent */
3/2	2026/09/18 20:57	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 6824 output: 28 thoughts: 457 Thoughts: Analyzing This Patch for Syzkaller Fuzzing Potential Okay, let's break this down. The user wants an evaluation of a patch for its fuzzing potential with syzkaller. Looks like we have a patch touching `kernel/bpf/verifier.c` and adding some tests in `tools/testing/selftests/bpf/`. My first instinct is to dive into the code changes in `kernel/bpf/verifier.c`. Specifically, it looks like this patch is adding `destroy_dynptrs_on_func_exit`, updating the logic of `destroy_if_dynptr_stack_slot`, and `prepare_func_exit` to use `destroy_dynptrs_on_func_exit`, and there's some new logic around handling `on_func_exit` and dynamic pointers (dynptrs). Essentially, the patch is aimed at cleaning up and validating dynamic pointers when returning from a BPF function. Key takeaway: it's about making sure derived slices from local dynptrs are invalidated after the function call! That's precisely the kind of low-level memory management stuff that gets fuzzers excited. Now, the core subsystem involved here is the BPF verifier. And that verifier is definitely reachable. We know that `bpf()` syscall and the `BPF_PROG_LOAD` command are the key entry points. Syzkaller loves attacking the BPF verifier! This makes it a prime target for fuzzing. So, definitely worth considering for `WorthFuzzing`. Checking my internal rules, this fits perfectly. The patch modifies BPF, which is a core subsystem: BPF falls squarely into the "any logic modifications in BPF" category. That checks out. Next, I need to figure out what kernel configurations are needed to enable this functionality. Let's check `kernel/bpf/Makefile`, `init/Kconfig` and `kernel/bpf/Kconfig`.
4/2	2026/09/18 20:57	tool	grepper	0m Args: { "Expression": "verifier.o", "PathPrefix": "kernel/bpf/" } Results: { "Output": "kernel/bpf/Makefile=7=CFLAGS_core.o += -Wno-override-init $(cflags-nogcse-yy)\nkernel/bpf/Makefile-8-\nkernel/bpf/Makefile:9:obj-$(CONFIG_BPF_SYSCALL) += syscall.o verifier.o inode.o helpers.o tnum.o cnum.o log.o token.o liveness.o const_fold.o diagnostics.o\nkernel/bpf/Makefile-10-obj-$(CONFIG_BPF_SYSCALL) += bpf_iter.o map_iter.o task_iter.o prog_iter.o link_iter.o\n--\nkernel/bpf/bpf_lsm.c=413=const struct bpf_prog_ops lsm_prog_ops = {\n--\nkernel/bpf/bpf_lsm.c-415-\nkernel/bpf/bpf_lsm.c:416:const struct bpf_verifier_ops lsm_verifier_ops = {\nkernel/bpf/bpf_lsm.c-417-\t.get_func_proto = bpf_lsm_func_proto,\n--\nkernel/bpf/bpf_struct_ops.c=64=static DEFINE_MUTEX(update_mutex);\n--\nkernel/bpf/bpf_struct_ops.c-68-\nkernel/bpf/bpf_struct_ops.c:69:const struct bpf_verifier_ops bpf_struct_ops_verifier_ops = {\nkernel/bpf/bpf_struct_ops.c-70-};\n--\nkernel/bpf/btf.c=5980=static struct btf btf_parse(const union bpf_attr attr, bpfptr_t uattr,\n--\nkernel/bpf/btf.c-5996-\nkernel/bpf/btf.c:5997:\t/* user could have requested verbose verifier output\nkernel/bpf/btf.c-5998-\t * and supplied buffer to store the verification trace\n--\nkernel/bpf/cgroup.c=1923=const struct bpf_prog_ops cg_dev_prog_ops = {\n--\nkernel/bpf/cgroup.c-1925-\nkernel/bpf/cgroup.c:1926:const struct bpf_verifier_ops cg_dev_verifier_ops = {\nkernel/bpf/cgroup.c-1927-\t.get_func_proto\t\t= cgroup_dev_func_proto,\n--\nkernel/bpf/cgroup.c=2478=static u32 sysctl_convert_ctx_access(enum bpf_access_type type,\n--\nkernel/bpf/cgroup.c-2541-\nkernel/bpf/cgroup.c:2542:const struct bpf_verifier_ops cg_sysctl_verifier_ops = {\nkernel/bpf/cgroup.c-2543-\t.get_func_proto\t\t= sysctl_func_proto,\n--\nkernel/bpf/cgroup.c=2756=static int cg_sockopt_get_prologue(struct bpf_insn insn_buf,\n--\nkernel/bpf/cgroup.c-2764-\nkernel/bpf/cgroup.c:2765:const struct bpf_verifier_ops cg_sockopt_verifier_ops = {\nkernel/bpf/cgroup.c-2766-\t.get_func_proto\t\t= cg_sockopt_func_proto,\n--\nkernel/bpf/fixups.c=773=int bpf_convert_ctx_accesses(struct bpf_verifier_env env)\n--\nkernel/bpf/fixups.c-775-\tstruct bpf_subprog_info subprogs = env-\u003esubprog_info;\nkernel/bpf/fixups.c:776:\tconst struct bpf_verifier_ops ops = env-\u003eops;\nkernel/bpf/fixups.c-777-\tint i, cnt, size, ctx_field_size, ret, delta = 0, epilogue_cnt = 0;\n--\nkernel/bpf/helpers.c-35-/* If kernel subsystem is allowing eBPF programs to call this function,\nkernel/bpf/helpers.c:36: * inside its own verifier_ops-\u003eget_func_proto() callback it should return\nkernel/bpf/helpers.c-37- * bpf_map_lookup_elem_proto, so that verifier can properly check the arguments\n--\nkernel/bpf/syscall.c=6630=syscall_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog prog)\n--\nkernel/bpf/syscall.c-6646-\nkernel/bpf/syscall.c:6647:const struct bpf_verifier_ops bpf_syscall_verifier_ops = {\nkernel/bpf/syscall.c-6648-\t.get_func_proto = syscall_prog_func_proto,\n--\nkernel/bpf/task_iter.c=992=__bpf_kfunc struct vm_area_struct bpf_iter_task_vma_next(struct bpf_iter_task_vma it)\n--\nkernel/bpf/task_iter.c-1010-\t/\nkernel/bpf/task_iter.c:1011:\t * The verifier only trusts vm_mm and vm_file (see\nkernel/bpf/task_iter.c-1012-\t * BTF_TYPE_SAFE_TRUSTED_OR_NULL in verifier.c). Take a reference\n--\nkernel/bpf/trampoline.c-17-/* dummy _ops. The verifier will operate on target program's ops. /\nkernel/bpf/trampoline.c:18:const struct bpf_verifier_ops bpf_extension_verifier_ops = {\nkernel/bpf/trampoline.c-19-};\n--\nkernel/bpf/verifier.c-40-\nkernel/bpf/verifier.c:41:static const struct bpf_verifier_ops const bpf_verifier_ops[] = {\nkernel/bpf/verifier.c-42-#define BPF_PROG_TYPE(_id, _name, prog_ctx_type, kern_ctx_type) \\\nkernel/bpf/verifier.c:43:\t[_id] = \u0026 _name ## _verifier_ops,\nkernel/bpf/verifier.c-44-#define BPF_MAP_TYPE(_id, _ops)\n--\nkernel/bpf/verifier.c=7394=enum {\n--\nkernel/bpf/verifier.c-7405- * For traditional PTR_TO_MAP_VALUE or PTR_TO_BTF_ID \| MEM_ALLOC, the verifier\nkernel/bpf/verifier.c:7406: * clears reg-\u003eid after value_or_null-\u003evalue transition, since the verifier only\nkernel/bpf/verifier.c-7407- * cares about the range of access to valid map value pointer and doesn't care\n--\nkernel/bpf/verifier.c=14921=static int adjust_ptr_min_max_vals(struct bpf_verifier_env env, struct bpf_insn insn,\n--\nkernel/bpf/verifier.c-15095-\t\t\t\tenv, \"This operation subtracts pointer register R%d from scalar register R%d. \"\nkernel/bpf/verifier.c:15096:\t\t\t\t\"The verifier only tracks pointer-minus-scalar arithmetic for allowed pointer types.\",\nkernel/bpf/verifier.c-15097-\t\t\t\tptr_regno, dst);\n--\nkernel/bpf/verifier.c=18060=bool bpf_get_call_summary(struct bpf_verifier_env env, struct bpf_insn call,\n--\nkernel/bpf/verifier.c-18125- \nkernel/bpf/verifier.c:18126: - if so, and if verifier or current JIT inlines the call to the\nkernel/bpf/verifier.c-18127- * bpf_fastcall function (e.g. a helper call), kernel removes unnecessary\n--\nkernel/bpf/verifier.c=20110=static int check_struct_ops_btf_id(struct bpf_verifier_env env)\n--\nkernel/bpf/verifier.c-20227-\tprog-\u003eaux-\u003eattach_func_name = mname;\nkernel/bpf/verifier.c:20228:\tenv-\u003eops = st_ops-\u003everifier_ops;\nkernel/bpf/verifier.c-20229-\n--\nkernel/bpf/verifier.c=20861=static int check_attach_btf_id(struct bpf_verifier_env env)\n--\nkernel/bpf/verifier.c-20900-\t\t /\nkernel/bpf/verifier.c:20901:\t\tenv-\u003eops = bpf_verifier_ops[tgt_prog-\u003etype];\nkernel/bpf/verifier.c-20902-\t\tprog-\u003eexpected_attach_type = tgt_prog-\u003eexpected_attach_type;\n--\nkernel/bpf/verifier.c=21550=int bpf_check(struct bpf_prog prog, union bpf_attr attr, bpfptr_t uattr,\n--\nkernel/bpf/verifier.c-21560-\t/* no program is valid /\nkernel/bpf/verifier.c:21561:\tif (ARRAY_SIZE(bpf_verifier_ops) == 0)\nkernel/bpf/verifier.c-21562-\t\treturn -EINVAL;\n--\nkernel/bpf/verifier.c-21572-\tenv-\u003eprog = prog;\nkernel/bpf/verifier.c:21573:\tenv-\u003eops = bpf_verifier_ops[env-\u003eprog-\u003etype];\nkernel/bpf/verifier.c-21574-\n--\nkernel/bpf/verifier.c-21581-\nkernel/bpf/verifier.c:21582:\t/* user could have requested verbose verifier output\nkernel/bpf/verifier.c-21583-\t * and supplied buffer to store the verification trace\n" }
5/2	2026/09/18 20:57	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 10298 output: 29 thoughts: 29 Thoughts: Okay, here's my summary, presented as a stream of thought: Kernel Configuration Dependencies - BPF_SYSCALL Alright, CONFIG_BPF_SYSCALL is essential – no question about it. I need to figure out exactly what it depends on. Best way to do this is to jump right into `init/Kconfig`. Let's see what the dependencies are, if any. I'm especially interested in figuring out if there are any gotchas in enabling it, or if it's dependent on any other core functionalities I need to know about. This will help me with my work today. I will focus my efforts on this config's dependencies for now.
6/2	2026/09/18 20:57	tool	grepper	0m Error: no matches Args: { "Expression": "config BPF_SYSCALL", "PathPrefix": "init/" } Results: { "error": "no matches" }
7/2	2026/09/18 20:57	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 10517 output: 21 thoughts: 14 Thoughts: Here's my attempt at summarizing the thought process, tailored for an expert audience: Investigating the BPF_SYSCALL Macro Okay, so I need to understand where `BPF_SYSCALL` is actually defined. This macro is crucial, obviously, for how we hook and track system calls with BPF, and I need to make sure I'm crystal clear on its implementation and potential implications. I can't start doing anything further until I know exactly what this macro expands to, where it's declared in the kernel source, and any dependencies it might have. This is a fundamental building block, so understanding its origin is non-negotiable before moving forward. Let's dig in and figure out the exact location and contents.
8/2	2026/09/18 20:57	tool	grepper	0m Args: { "Expression": "config BPF_SYSCALL" } Results: { "Output": "kernel/bpf/Kconfig=29=menu \"BPF subsystem\"\nkernel/bpf/Kconfig-30-\nkernel/bpf/Kconfig:31:config BPF_SYSCALL\nkernel/bpf/Kconfig-32-\tbool \"Enable bpf() system call\"\n" }
9/2	2026/09/18 20:57	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 10793 output: 34 thoughts: 17 Thoughts: Here's my attempt at summarizing the thought process, tailored for an expert audience and written in the first person: Kernel Configuration Context Okay, let's dive in. I need to understand the configuration options related to BPF, specifically within the kernel. The goal is to get a solid grasp of how these features are exposed and controlled. I'll focus on `kernel/bpf/Kconfig`, starting around line 31. This is where I'd expect to find the core BPF options and dependencies defined. I need to refresh my mental map of how the Kconfig system structures feature toggles, dependencies, and default values. Specifically, I am looking to quickly orient to the main configuration option names (e.g., `CONFIG_BPF`, `CONFIG_BPF_JIT`), their dependencies on each other and other kernel components, and any associated help text. I am interested in quickly understanding the implications of enabling or disabling various BPF-related features. This should give me a good handle on how the kernel exposes and controls BPF functionality from a build and configuration perspective.
10/2	2026/09/18 20:57	tool	read-file	0m Args: { "File": "kernel/bpf/Kconfig", "FirstLine": 25, "LineCount": 30 } Results: { "Contents": " 25:\t# default for kernels that were compiled with BPF JIT support.\n 26:\tconfig ARCH_WANT_DEFAULT_BPF_JIT\n 27:\t\tbool\n 28:\t\n 29:\tmenu \"BPF subsystem\"\n 30:\t\n 31:\tconfig BPF_SYSCALL\n 32:\t\tbool \"Enable bpf() system call\"\n 33:\t\tselect BPF\n 34:\t\tselect IRQ_WORK\n 35:\t\tselect NEED_TASKS_RCU\n 36:\t\tselect TASKS_TRACE_RCU\n 37:\t\tselect BINARY_PRINTF\n 38:\t\tselect NET_SOCK_MSG if NET\n 39:\t\tselect NET_XGRESS if NET\n 40:\t\tselect PAGE_POOL if NET\n 41:\t\tdefault n\n 42:\t\thelp\n 43:\t\t Enable the bpf() system call that allows to manipulate BPF programs\n 44:\t\t and maps via file descriptors.\n 45:\t\n 46:\tconfig BPF_JIT\n 47:\t\tbool \"Enable BPF Just In Time compiler\"\n 48:\t\tdepends on BPF\n 49:\t\tdepends on HAVE_CBPF_JIT \|\| HAVE_EBPF_JIT\n 50:\t\tselect EXECMEM\n 51:\t\thelp\n 52:\t\t BPF programs are normally handled by a BPF interpreter. This option\n 53:\t\t allows the kernel to generate native code when a program is loaded\n 54:\t\t into the kernel. This will significantly speed-up processing of BPF\n" }
11/2	2026/09/18 20:57	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 11478 output: 30 thoughts: 201 Thoughts: Analyzing BPF Functionality Changes Okay, so `BPF_SYSCALL` seems pretty straightforward; it's a select statement for BPF without any explicit dependencies. Now, let's dive into the actual code changes and what's been touched. I need to understand the implications of these modifications within the BPF ecosystem. It looks like the `kernel/bpf/verifier.c` file is the focus. I see a new function, `destroy_dynptrs_on_func_exit`, that's immediately interesting. Then there are some modifications to `destroy_if_dynptr_stack_slot`, `prepare_func_exit`, and a few related function calls. Specifically, the verifier now seems to be more concerned with dynamic pointer management, as indicated by the integration of `destroy_if_dynptr_stack_slot` within `mark_stack_slots_dynptr`, `check_stack_write_fixed_off`, and `check_stack_write_var_off`. This likely has to do with how the BPF verifier handles pointers on the stack, which is critical for security and stability. I'm particularly interested in `prepare_func_exit`. Since it's been modified, I need to know how it's being used now. I'll check its callers and its overall function. Understanding its invocation context will be key to grasping the core changes. This pointer stack management looks significant.
12/2	2026/09/18 20:57	tool	grepper	0m Args: { "Expression": "prepare_func_exit", "PathPrefix": "kernel/bpf/" } Results: { "Output": "kernel/bpf/verifier.c=11012=static bool retval_range_within(struct bpf_retval_range range, const struct bpf_reg_state reg)\n--\nkernel/bpf/verifier.c-11019-\nkernel/bpf/verifier.c:11020:static int prepare_func_exit(struct bpf_verifier_env env, int insn_idx)\nkernel/bpf/verifier.c-11021-{\n--\nkernel/bpf/verifier.c=11514=static int check_helper_call(struct bpf_verifier_env env, struct bpf_insn insn,\n--\nkernel/bpf/verifier.c-12014-\t\t\t frame. A callback frame cannot be left that way because\nkernel/bpf/verifier.c:12015:\t\t\t * prepare_func_exit() would apply its return contract to the\nkernel/bpf/verifier.c-12016-\t\t\t * unknown R0 synthesized below. Stack-depth validation rejects\n--\nkernel/bpf/verifier.c-12028-\t\t\tmark_reg_unknown(env, regs, BPF_REG_0);\nkernel/bpf/verifier.c:12029:\t\t\terr = prepare_func_exit(env, \u0026env-\u003einsn_idx);\nkernel/bpf/verifier.c-12030-\t\t\tif (err)\n--\nkernel/bpf/verifier.c=17669=static int check_ld_abs(struct bpf_verifier_env env, struct bpf_insn insn)\n--\nkernel/bpf/verifier.c-17749-\t\tmark_reg_known_zero(env, regs, BPF_REG_0);\nkernel/bpf/verifier.c:17750:\t\terr = prepare_func_exit(env, \u0026env-\u003einsn_idx);\nkernel/bpf/verifier.c-17751-\t\tif (err)\n--\nkernel/bpf/verifier.c=18473=static int process_bpf_exit_full(struct bpf_verifier_env env,\n--\nkernel/bpf/verifier.c-18479-\t/ We must do check_reference_leak here before\nkernel/bpf/verifier.c:18480:\t * prepare_func_exit to handle the case when\nkernel/bpf/verifier.c-18481-\t * state-\u003ecurframe \u003e 0, it may be a callback function,\n--\nkernel/bpf/verifier.c-18491-\nkernel/bpf/verifier.c:18492:\t/* The side effect of the prepare_func_exit which is\nkernel/bpf/verifier.c-18493-\t * being skipped is that it frees bpf_func_state.\n--\nkernel/bpf/verifier.c-18505-\t\t/* exit from nested function */\nkernel/bpf/verifier.c:18506:\t\terr = prepare_func_exit(env, \u0026env-\u003einsn_idx);\nkernel/bpf/verifier.c-18507-\t\tif (err)\n" }
13/2	2026/09/18 20:57	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 12806 output: 36 thoughts: 730 Thoughts: Analyzing BPF Verifier Function Targeting for Fuzzing Okay, so I'm looking at how we can best target specific BPF verifier functions with fuzzing, specifically in relation to the changes we're making. The initial thought was to consider `prepare_func_exit` because it's called in places like `check_helper_call` and `process_bpf_exit_full`. Then I expanded to also look at `destroy_if_dynptr_stack_slot` and `destroy_dynptrs_on_func_exit`, and realized these are static functions within `kernel/bpf/verifier.c`. A key question popped up: Can static functions within `.c` files be directly targeted by fuzzing tools like kcov/syzkaller? The answer is yes, generally, unless the compiler completely inlines them. They should have symbol addresses. This led me to Section 4 of the documentation, which is super relevant. It specifically highlights the difference between static inlines in headers (.h) and static functions in .c files. The former can't be directly targeted because they lack distinct symbols. Now, focusing on the .c file functions, the list includes: `destroy_dynptrs_on_func_exit`, `destroy_if_dynptr_stack_slot`, `prepare_func_exit`, and `process_bpf_exit_full`. These seem like strong candidates, especially since they implement some logic that we're altering or adding. I considered `bpf_check` as a possibility, since it's called on every BPF program load, but then remembered the "AVOID UBIQUITOUS LIFECYCLE HOT-PATHS" guideline. `bpf_check` is probably too broad and would dilute the fuzzing effort. We want to be specific, and target functions that are directly related to the new or modified logic. Therefore, the revised list of functions to focus on for fuzzing is: `destroy_dynptrs_on_func_exit`, `destroy_if_dynptr_stack_slot`, `prepare_func_exit`, and `process_bpf_exit_full`. Now the next step is to examine their implementation to assess if they're substantial enough and not readily inlined. Let's start by reading `destroy_if_dynptr_stack_slot`.
14/2	2026/09/18 20:57	tool	read-file	0m Args: { "File": "kernel/bpf/verifier.c", "FirstLine": 860, "LineCount": 50 } Results: { "Contents": " 860:\t\t\t * A callee-local dynptr is destroyed when its stack frame goes\n 861:\t\t\t * away. Apply the normal stack-slot teardown so references cannot\n 862:\t\t\t * be lost and slices derived from that dynptr are invalidated.\n 863:\t\t\t /\n 864:\t\t\terr = destroy_if_dynptr_stack_slot(env, callee, i, true);\n 865:\t\t\tif (err)\n 866:\t\t\t\treturn err;\n 867:\t\t}\n 868:\t\n 869:\t\treturn 0;\n 870:\t}\n 871:\t\n 872:\tstatic int destroy_if_dynptr_stack_slot(struct bpf_verifier_env env,\n 873:\t\t\t\t\t\tstruct bpf_func_state state, int spi,\n 874:\t\t\t\t\t\tbool on_func_exit)\n 875:\t{\n 876:\t\tint err = 0;\n 877:\t\n 878:\t\t/ We always ensure that STACK_DYNPTR is never set partially,\n 879:\t\t * hence just checking for slot_type[0] is enough. This is\n 880:\t\t * different for STACK_SPILL, where it may be only set for\n 881:\t\t * 1 byte, so code has to use is_spilled_reg.\n 882:\t\t /\n 883:\t\tif (state-\u003estack[spi].slot_type[0] != STACK_DYNPTR)\n 884:\t\t\treturn 0;\n 885:\t\n 886:\t\t/ Reposition spi to first slot /\n 887:\t\tif (!state-\u003estack[spi].spilled_ptr.dynptr.first_slot)\n 888:\t\t\tspi = spi + 1;\n 889:\t\n 890:\t\t/\n 891:\t\t * A referenced dynptr can be overwritten only if there is at\n 892:\t\t * least one other dynptr sharing the same virtual ref parent,\n 893:\t\t * ensuring the reference can still be properly released.\n 894:\t\t */\n 895:\t\tif (dynptr_type_referenced(state-\u003estack[spi].spilled_ptr.dynptr.type) \u0026\u0026\n 896:\t\t dynptr_ref_cnt(env, state-\u003estack[spi].spilled_ptr.parent_id) \u003c= 1) {\n 897:\t\t\tif (on_func_exit) {\n 898:\t\t\t\tverbose(env, \"cannot return with referenced dynptr in callee stack\\n\");\n 899:\t\t\t\tbpf_diag_res(env, env-\u003einsn_idx,\n 900:\t\t\t\t\t \"referenced dynptr on function return\",\n 901:\t\t\t\t\t \"The departing stack frame contains the last dynptr that can release a referenced resource.\",\n 902:\t\t\t\t\t \"Release the referenced resource before returning from this function.\");\n 903:\t\t\t\treturn -EINVAL;\n 904:\t\t\t}\n 905:\t\n 906:\t\t\tverbose(env, \"cannot overwrite referenced dynptr\\n\");\n 907:\t\t\tbpf_diag_res(\n 908:\t\t\t\tenv, env-\u003einsn_idx, \"referenced dynptr overwrite\",\n 909:\t\t\t\t\"This stack slot contains a dynptr that owns or protects a referenced resource. Overwriting the last dynptr for that resource would lose the verifier-tracked release path.\",\n" }
15/2	2026/09/18 20:57	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 14945 output: 36 thoughts: 19 Thoughts: Okay, here's my interpretation of that thought process, assuming I'm deep in the weeds of some code, probably related to memory management or dynamic pointers, and I'm quite familiar with the function `destroy_if_dynptr_stack_slot`: Let's Dig into `destroy_if_dynptr_stack_slot` Alright, so I'm looking at this particular piece of the puzzle... I'm pretty sure I know what `destroy_if_dynptr_stack_slot` should be doing, based on the naming convention and where it's probably being used. It's almost certainly related to cleaning up, deallocating, or at least resetting some dynamically allocated memory, likely pointers residing on the stack. I need to refresh myself on the details, though, to ensure I'm remembering the specifics correctly. I've got a mental model of how this whole system works – the interactions between the stack, heap, these dynamic pointers – but I need to make sure this `destroy_if_dynptr_stack_slot` function is behaving as expected, and that it's correctly integrated into the broader resource management. Let's get the full context to see how it is supposed to be working.
16/2	2026/09/18 20:57	tool	read-file	0m Args: { "File": "kernel/bpf/verifier.c", "FirstLine": 910, "LineCount": 40 } Results: { "Contents": " 910:\t\t\t\t\"Release or clone the dynptr so another live dynptr still tracks the referenced resource before overwriting this stack slot.\");\n 911:\t\t\treturn -EINVAL;\n 912:\t\t}\n 913:\t\n 914:\t\t/* Invalidate the dynptr and any derived slices /\n 915:\t\terr = release_reference(env, state-\u003estack[spi].spilled_ptr.id);\n 916:\t\tif (!err) {\n 917:\t\t\tmark_stack_slot_scratched(env, spi);\n 918:\t\t\tmark_stack_slot_scratched(env, spi - 1);\n 919:\t\t}\n 920:\t\n 921:\t\treturn err;\n 922:\t}\n 923:\t\n 924:\tstatic bool is_dynptr_reg_valid_uninit(struct bpf_verifier_env env, struct bpf_reg_state reg)\n 925:\t{\n 926:\t\tint spi;\n 927:\t\n 928:\t\tif (reg-\u003etype == CONST_PTR_TO_DYNPTR)\n 929:\t\t\treturn false;\n 930:\t\n 931:\t\tspi = dynptr_get_spi(env, reg);\n 932:\t\n 933:\t\t/ -ERANGE (i.e. spi not falling into allocated stack slots) isn't an\n 934:\t\t * error because this just means the stack state hasn't been updated yet.\n 935:\t\t * We will do check_mem_access to check and update stack bounds later.\n 936:\t\t /\n 937:\t\tif (spi \u003c 0 \u0026\u0026 spi != -ERANGE)\n 938:\t\t\treturn false;\n 939:\t\n 940:\t\t/ We don't need to check if the stack slots are marked by previous\n 941:\t\t * dynptr initializations because we allow overwriting existing unreferenced\n 942:\t\t * STACK_DYNPTR slots, see mark_stack_slots_dynptr which calls\n 943:\t\t * destroy_if_dynptr_stack_slot to ensure dynptr objects at the slots we are\n 944:\t\t * touching are completely destructed before we reinitialize them for a new\n 945:\t\t * one. For referenced ones, destroy_if_dynptr_stack_slot returns an error early\n 946:\t\t * instead of delaying it until the end where the user will get \"Unreleased\n 947:\t\t * reference\" error.\n 948:\t\t */\n 949:\t\treturn true;\n" }
17/2	2026/09/18 20:57	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 15930 output: 38 thoughts: 22 Thoughts: Here's my attempt at summarizing the thought process, tailored for an expert audience and written in the first person: Analyzing `prepare_func_exit` in Detail Okay, so I'm diving back in to examine `prepare_func_exit`. The context is definitely important here, and I'm homing in on the section around line 11070. What are the key operations occurring at this point? I need to understand how the function is handling stack unwinding, resource cleanup, and possibly any error handling immediately prior to returning control. It's crucial to ensure that any potential side effects or state changes are correctly addressed to maintain program integrity. My immediate focus is identifying any subtle race conditions or unexpected behavior that could be triggered in specific execution scenarios. Understanding the interaction with the overall execution context is paramount.
18/2	2026/09/18 20:58	tool	read-file	0m Args: { "File": "kernel/bpf/verifier.c", "FirstLine": 11070, "LineCount": 40 } Results: { "Contents": "11070:\t\t\t * return to the caller whatever the callee had in the\n11071:\t\t\t * return register(s)\n11072:\t\t\t /\n11073:\t\t\tfor (i = 0; i \u003c nregs; i++) {\n11074:\t\t\t\tu32 regno = ret_regs[i];\n11075:\t\n11076:\t\t\t\tbpf_diag_mod_begin(env, \u0026caller-\u003eregs[regno], \u0026callee-\u003eregs[regno],\n11077:\t\t\t\t\t\t BPF_DIAG_MOD_WRITE);\n11078:\t\t\t\tcaller-\u003eregs[regno] = callee-\u003eregs[regno];\n11079:\t\t\t\tbpf_diag_mod_end(env);\n11080:\t\t\t}\n11081:\t\t}\n11082:\t\terr = destroy_dynptrs_on_func_exit(env, callee);\n11083:\t\tif (err)\n11084:\t\t\treturn err;\n11085:\t\n11086:\t\t/ for callbacks like bpf_loop or bpf_for_each_map_elem go back to callsite,\n11087:\t\t * there function call logic would reschedule callback visit. If iteration\n11088:\t\t * converges is_state_visited() would prune that visit eventually.\n11089:\t\t /\n11090:\t\tin_callback_fn = callee-\u003ein_callback_fn;\n11091:\t\tif (in_callback_fn)\n11092:\t\t\tinsn_idx = callee-\u003ecallsite;\n11093:\t\telse\n11094:\t\t\tinsn_idx = callee-\u003ecallsite + 1;\n11095:\t\n11096:\t\tif (env-\u003elog.level \u0026 BPF_LOG_LEVEL) {\n11097:\t\t\tverbose(env, \"returning from callee:\\n\");\n11098:\t\t\tprint_verifier_state(env, state, callee-\u003eframeno, true);\n11099:\t\t\tverbose(env, \"to caller at %d:\\n\", insn_idx);\n11100:\t\t\tprint_verifier_state(env, state, caller-\u003eframeno, true);\n11101:\t\t}\n11102:\t\taccount_processed_insns(env, callee, caller);\n11103:\t\t/* clear everything in the callee. In case of exceptional exits using\n11104:\t\t * bpf_throw, this will be done by copy_verifier_state for extra frames. /\n11105:\t\tfree_func_state(callee);\n11106:\t\tstate-\u003eframe[state-\u003ecurframe--] = NULL;\n11107:\t\tinvalidate_outgoing_stack_args(env, caller);\n11108:\t\n11109:\t\t/ for callbacks widen imprecise scalars to make programs like below verify:\n" }
19/2	2026/09/18 20:58	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 16917 output: 31 thoughts: 537 Thoughts: Fuzzing the BPF Verifier: A Deep Dive into Function Exit and Dynamic Pointer Handling Okay, let's break this down. My initial assessment is that `prepare_func_exit` is a key function to target. It's the entry point when we're leaving a function, subroutine, or callback within the BPF verifier. The verifier goes through a `destroy_dynptrs_on_func_exit` process, and that's where things get interesting. Specifically, it iterates through the callee's stack slots, searches for `STACK_DYNPTR` slots, and then uses `destroy_if_dynptr_stack_slot` to handle them. This part is crucial for making sure we're correctly releasing resources on function exit. Here's the scenario: if a dynptr is referenced and its `ref_cnt` is less than or equal to 1, we get an error, and the program is rejected. It's essentially preventing the return of a function with dangling pointers. Otherwise, the dynptr and any derived slices are invalidated using `release_reference`. This lifecycle management is complex, and the code here is executable, so fuzzing this is certainly valuable. Given the potential for subtle interactions with things like state pruning, callback verification, loop handling, subprograms, and reference tracking, this is a prime target for syzkaller. Any modifications to how dynptrs are tracked, how slices are invalidated, or how function exits are verified could open up vulnerabilities. Now, let's hone in on the specific functions. I've got a list of focus symbols: `destroy_dynptrs_on_func_exit`, `destroy_if_dynptr_stack_slot`, `prepare_func_exit`, `mark_stack_slots_dynptr`, `check_stack_write_fixed_off`, and `check_stack_write_var_off`. Based on their relationship to `prepare_func_exit`, `destroy_dynptrs_on_func_exit` and `destroy_if_dynptr_stack_slot` look like the most important ones. They seem tightly coupled, which is what I'd expect. We also have `process_bpf_exit_full`, where `BPF_EXIT` instructions are handled. Let's drill down: * `prepare_func_exit` is being directly modified and calls `destroy_dynptrs_on_func_exit` which is good to see as an indicator of it's importance to the code. * `destroy_if_dynptr_stack_slot` is also being modified directly * `destroy_dynptrs_on_func_exit` is new * `mark_stack_slots_dynptr` is where dynptrs are initialized on the stack. Okay, let's move on to configuration checks. The code relies on `CONFIG_BPF_SYSCALL`, and I need to determine if there are additional configuration dependencies for the handling of dynptrs or `struct_ops`. I'll need to double-check if any specific configurations are needed for dynptrs.
20/2	2026/09/18 20:58	tool	grepper	0m Args: { "Expression": "bpf_dynptr_", "PathPrefix": "kernel/bpf/" } Results: { "Output": "\nFull output is too long, showing 500 out of 786 lines.\nUse more precise expression if possible.\n\nkernel/bpf/crypto.c=270=static int bpf_crypto_crypt(const struct bpf_crypto_ctx ctx,\nkernel/bpf/crypto.c:271:\t\t\t const struct bpf_dynptr_kern src,\nkernel/bpf/crypto.c:272:\t\t\t const struct bpf_dynptr_kern dst,\nkernel/bpf/crypto.c:273:\t\t\t const struct bpf_dynptr_kern siv,\nkernel/bpf/crypto.c-274-\t\t\t bool decrypt)\n--\nkernel/bpf/crypto.c-280-\nkernel/bpf/crypto.c:281:\tif (__bpf_dynptr_is_rdonly(dst))\nkernel/bpf/crypto.c-282-\t\treturn -EINVAL;\nkernel/bpf/crypto.c-283-\nkernel/bpf/crypto.c:284:\tsiv_len = siv ? __bpf_dynptr_size(siv) : 0;\nkernel/bpf/crypto.c:285:\tsrc_len = __bpf_dynptr_size(src);\nkernel/bpf/crypto.c:286:\tdst_len = __bpf_dynptr_size(dst);\nkernel/bpf/crypto.c-287-\tif (!src_len \|\| !dst_len \|\| src_len \u003e dst_len)\n--\nkernel/bpf/crypto.c-292-\nkernel/bpf/crypto.c:293:\tpsrc = __bpf_dynptr_data(src, src_len);\nkernel/bpf/crypto.c-294-\tif (!psrc)\nkernel/bpf/crypto.c-295-\t\treturn -EINVAL;\nkernel/bpf/crypto.c:296:\tpdst = __bpf_dynptr_data_rw(dst, dst_len);\nkernel/bpf/crypto.c-297-\tif (!pdst)\n--\nkernel/bpf/crypto.c-299-\nkernel/bpf/crypto.c:300:\tpiv = siv_len ? __bpf_dynptr_data_rw(siv, siv_len) : NULL;\nkernel/bpf/crypto.c-301-\tif (siv_len \u0026\u0026 !piv)\n--\nkernel/bpf/crypto.c=319=__bpf_kfunc int bpf_crypto_decrypt(struct bpf_crypto_ctx ctx,\n--\nkernel/bpf/crypto.c-323-{\nkernel/bpf/crypto.c:324:\tconst struct bpf_dynptr_kern src_kern = (struct bpf_dynptr_kern )src;\nkernel/bpf/crypto.c:325:\tconst struct bpf_dynptr_kern dst_kern = (struct bpf_dynptr_kern )dst;\nkernel/bpf/crypto.c:326:\tconst struct bpf_dynptr_kern siv_kern = (struct bpf_dynptr_kern )siv__nullable;\nkernel/bpf/crypto.c-327-\n--\nkernel/bpf/crypto.c=340=__bpf_kfunc int bpf_crypto_encrypt(struct bpf_crypto_ctx ctx,\n--\nkernel/bpf/crypto.c-344-{\nkernel/bpf/crypto.c:345:\tconst struct bpf_dynptr_kern src_kern = (struct bpf_dynptr_kern )src;\nkernel/bpf/crypto.c:346:\tconst struct bpf_dynptr_kern dst_kern = (struct bpf_dynptr_kern )dst;\nkernel/bpf/crypto.c:347:\tconst struct bpf_dynptr_kern siv_kern = (struct bpf_dynptr_kern )siv__nullable;\nkernel/bpf/crypto.c-348-\n--\nkernel/bpf/helpers.c=1744=static const struct bpf_func_proto bpf_kptr_xchg_proto = {\n--\nkernel/bpf/helpers.c-1753-\nkernel/bpf/helpers.c:1754:struct bpf_dynptr_file_impl {\nkernel/bpf/helpers.c-1755-\tstruct freader freader;\nkernel/bpf/helpers.c:1756:\t/* 64 bit offset and size overriding 32 bit ones in bpf_dynptr_kern /\nkernel/bpf/helpers.c-1757-\tu64 offset;\n--\nkernel/bpf/helpers.c-1768-\nkernel/bpf/helpers.c:1769:bool __bpf_dynptr_is_rdonly(const struct bpf_dynptr_kern ptr)\nkernel/bpf/helpers.c-1770-{\n--\nkernel/bpf/helpers.c-1773-\nkernel/bpf/helpers.c:1774:void bpf_dynptr_set_rdonly(struct bpf_dynptr_kern ptr)\nkernel/bpf/helpers.c-1775-{\n--\nkernel/bpf/helpers.c-1778-\nkernel/bpf/helpers.c:1779:static void bpf_dynptr_set_type(struct bpf_dynptr_kern ptr, enum bpf_dynptr_type type)\nkernel/bpf/helpers.c-1780-{\n--\nkernel/bpf/helpers.c-1783-\nkernel/bpf/helpers.c:1784:static enum bpf_dynptr_type bpf_dynptr_get_type(const struct bpf_dynptr_kern ptr)\nkernel/bpf/helpers.c-1785-{\n--\nkernel/bpf/helpers.c-1788-\nkernel/bpf/helpers.c:1789:u64 __bpf_dynptr_size(const struct bpf_dynptr_kern ptr)\nkernel/bpf/helpers.c-1790-{\nkernel/bpf/helpers.c:1791:\tif (bpf_dynptr_get_type(ptr) == BPF_DYNPTR_TYPE_FILE) {\nkernel/bpf/helpers.c:1792:\t\tstruct bpf_dynptr_file_impl df = ptr-\u003edata;\nkernel/bpf/helpers.c-1793-\n--\nkernel/bpf/helpers.c-1799-\nkernel/bpf/helpers.c:1800:static void bpf_dynptr_advance_offset(struct bpf_dynptr_kern ptr, u64 off)\nkernel/bpf/helpers.c-1801-{\nkernel/bpf/helpers.c:1802:\tif (bpf_dynptr_get_type(ptr) == BPF_DYNPTR_TYPE_FILE) {\nkernel/bpf/helpers.c:1803:\t\tstruct bpf_dynptr_file_impl df = ptr-\u003edata;\nkernel/bpf/helpers.c-1804-\n--\nkernel/bpf/helpers.c-1810-\nkernel/bpf/helpers.c:1811:static void bpf_dynptr_set_size(struct bpf_dynptr_kern ptr, u64 new_size)\nkernel/bpf/helpers.c-1812-{\n--\nkernel/bpf/helpers.c-1814-\nkernel/bpf/helpers.c:1815:\tif (bpf_dynptr_get_type(ptr) == BPF_DYNPTR_TYPE_FILE) {\nkernel/bpf/helpers.c:1816:\t\tstruct bpf_dynptr_file_impl df = ptr-\u003edata;\nkernel/bpf/helpers.c-1817-\n--\nkernel/bpf/helpers.c-1823-\nkernel/bpf/helpers.c:1824:int bpf_dynptr_check_size(u64 size)\nkernel/bpf/helpers.c-1825-{\n--\nkernel/bpf/helpers.c-1828-\nkernel/bpf/helpers.c:1829:static int bpf_file_fetch_bytes(struct bpf_dynptr_file_impl df, u64 offset, void buf, u64 len)\nkernel/bpf/helpers.c-1830-{\n--\nkernel/bpf/helpers.c-1847-\nkernel/bpf/helpers.c:1848:void bpf_dynptr_init(struct bpf_dynptr_kern ptr, void data,\nkernel/bpf/helpers.c:1849:\t\t enum bpf_dynptr_type type, u32 offset, u32 size)\nkernel/bpf/helpers.c-1850-{\n--\nkernel/bpf/helpers.c-1853-\tptr-\u003esize = size;\nkernel/bpf/helpers.c:1854:\tbpf_dynptr_set_type(ptr, type);\nkernel/bpf/helpers.c-1855-}\nkernel/bpf/helpers.c-1856-\nkernel/bpf/helpers.c:1857:void bpf_dynptr_set_null(struct bpf_dynptr_kern ptr)\nkernel/bpf/helpers.c-1858-{\n--\nkernel/bpf/helpers.c-1861-\nkernel/bpf/helpers.c:1862:BPF_CALL_4(bpf_dynptr_from_mem, void , data, u64, size, u64, flags, struct bpf_dynptr_kern , ptr)\nkernel/bpf/helpers.c-1863-{\n--\nkernel/bpf/helpers.c-1867-\nkernel/bpf/helpers.c:1868:\terr = bpf_dynptr_check_size(size);\nkernel/bpf/helpers.c-1869-\tif (err)\n--\nkernel/bpf/helpers.c-1877-\nkernel/bpf/helpers.c:1878:\tbpf_dynptr_init(ptr, data, BPF_DYNPTR_TYPE_LOCAL, 0, size);\nkernel/bpf/helpers.c-1879-\n--\nkernel/bpf/helpers.c-1882-error:\nkernel/bpf/helpers.c:1883:\tbpf_dynptr_set_null(ptr);\nkernel/bpf/helpers.c-1884-\treturn err;\n--\nkernel/bpf/helpers.c-1886-\nkernel/bpf/helpers.c:1887:static const struct bpf_func_proto bpf_dynptr_from_mem_proto = {\nkernel/bpf/helpers.c:1888:\t.func\t\t= bpf_dynptr_from_mem,\nkernel/bpf/helpers.c-1889-\t.gpl_only\t= false,\n--\nkernel/bpf/helpers.c-1896-\nkernel/bpf/helpers.c:1897:static int __bpf_dynptr_read(void dst, u64 len, const struct bpf_dynptr_kern src,\nkernel/bpf/helpers.c-1898-\t\t\t u64 offset, u64 flags)\nkernel/bpf/helpers.c-1899-{\nkernel/bpf/helpers.c:1900:\tenum bpf_dynptr_type type;\nkernel/bpf/helpers.c-1901-\tint err;\n--\nkernel/bpf/helpers.c-1905-\nkernel/bpf/helpers.c:1906:\terr = bpf_dynptr_check_off_len(src, offset, len);\nkernel/bpf/helpers.c-1907-\tif (err)\n--\nkernel/bpf/helpers.c-1909-\nkernel/bpf/helpers.c:1910:\ttype = bpf_dynptr_get_type(src);\nkernel/bpf/helpers.c-1911-\n--\nkernel/bpf/helpers.c-1915-\t\t/* Source and destination may possibly overlap, hence use memmove to\nkernel/bpf/helpers.c:1916:\t\t * copy the data. E.g. bpf_dynptr_from_mem may create two dynptr\nkernel/bpf/helpers.c-1917-\t\t * pointing to overlapping PTR_TO_MAP_VALUE regions.\n--\nkernel/bpf/helpers.c-1930-\tdefault:\nkernel/bpf/helpers.c:1931:\t\tWARN_ONCE(true, \"bpf_dynptr_read: unknown dynptr type %d\\n\", type);\nkernel/bpf/helpers.c-1932-\t\treturn -EFAULT;\n--\nkernel/bpf/helpers.c-1935-\nkernel/bpf/helpers.c:1936:BPF_CALL_5(bpf_dynptr_read, void , dst, u64, len, const struct bpf_dynptr_kern , src,\nkernel/bpf/helpers.c-1937-\t u64, offset, u64, flags)\nkernel/bpf/helpers.c-1938-{\nkernel/bpf/helpers.c:1939:\treturn __bpf_dynptr_read(dst, len, src, offset, flags);\nkernel/bpf/helpers.c-1940-}\nkernel/bpf/helpers.c-1941-\nkernel/bpf/helpers.c:1942:static const struct bpf_func_proto bpf_dynptr_read_proto = {\nkernel/bpf/helpers.c:1943:\t.func\t\t= bpf_dynptr_read,\nkernel/bpf/helpers.c-1944-\t.gpl_only\t= false,\n--\nkernel/bpf/helpers.c-1952-\nkernel/bpf/helpers.c:1953:int __bpf_dynptr_write(const struct bpf_dynptr_kern dst, u64 offset, void src,\nkernel/bpf/helpers.c-1954-\t\t u64 len, u64 flags)\nkernel/bpf/helpers.c-1955-{\nkernel/bpf/helpers.c:1956:\tenum bpf_dynptr_type type;\nkernel/bpf/helpers.c-1957-\tint err;\nkernel/bpf/helpers.c-1958-\nkernel/bpf/helpers.c:1959:\tif (!dst-\u003edata \|\| __bpf_dynptr_is_rdonly(dst))\nkernel/bpf/helpers.c-1960-\t\treturn -EINVAL;\nkernel/bpf/helpers.c-1961-\nkernel/bpf/helpers.c:1962:\terr = bpf_dynptr_check_off_len(dst, offset, len);\nkernel/bpf/helpers.c-1963-\tif (err)\n--\nkernel/bpf/helpers.c-1965-\nkernel/bpf/helpers.c:1966:\ttype = bpf_dynptr_get_type(dst);\nkernel/bpf/helpers.c-1967-\n--\nkernel/bpf/helpers.c-1973-\t\t/* Source and destination may possibly overlap, hence use memmove to\nkernel/bpf/helpers.c:1974:\t\t * copy the data. E.g. bpf_dynptr_from_mem may create two dynptr\nkernel/bpf/helpers.c-1975-\t\t * pointing to overlapping PTR_TO_MAP_VALUE regions.\n--\nkernel/bpf/helpers.c-1989-\tdefault:\nkernel/bpf/helpers.c:1990:\t\tWARN_ONCE(true, \"bpf_dynptr_write: unknown dynptr type %d\\n\", type);\nkernel/bpf/helpers.c-1991-\t\treturn -EFAULT;\n--\nkernel/bpf/helpers.c-1994-\nkernel/bpf/helpers.c:1995:BPF_CALL_5(bpf_dynptr_write, const struct bpf_dynptr_kern , dst, u64, offset, void , src,\nkernel/bpf/helpers.c-1996-\t u64, len, u64, flags)\nkernel/bpf/helpers.c-1997-{\nkernel/bpf/helpers.c:1998:\treturn __bpf_dynptr_write(dst, offset, src, len, flags);\nkernel/bpf/helpers.c-1999-}\nkernel/bpf/helpers.c-2000-\nkernel/bpf/helpers.c:2001:static const struct bpf_func_proto bpf_dynptr_write_proto = {\nkernel/bpf/helpers.c:2002:\t.func\t\t= bpf_dynptr_write,\nkernel/bpf/helpers.c-2003-\t.gpl_only\t= false,\n--\nkernel/bpf/helpers.c-2011-\nkernel/bpf/helpers.c:2012:BPF_CALL_3(bpf_dynptr_data, const struct bpf_dynptr_kern , ptr, u64, offset, u64, len)\nkernel/bpf/helpers.c-2013-{\nkernel/bpf/helpers.c:2014:\tenum bpf_dynptr_type type;\nkernel/bpf/helpers.c-2015-\tint err;\n--\nkernel/bpf/helpers.c-2019-\nkernel/bpf/helpers.c:2020:\terr = bpf_dynptr_check_off_len(ptr, offset, len);\nkernel/bpf/helpers.c-2021-\tif (err)\n--\nkernel/bpf/helpers.c-2023-\nkernel/bpf/helpers.c:2024:\tif (__bpf_dynptr_is_rdonly(ptr))\nkernel/bpf/helpers.c-2025-\t\treturn 0;\nkernel/bpf/helpers.c-2026-\nkernel/bpf/helpers.c:2027:\ttype = bpf_dynptr_get_type(ptr);\nkernel/bpf/helpers.c-2028-\n--\nkernel/bpf/helpers.c-2035-\tcase BPF_DYNPTR_TYPE_SKB_META:\nkernel/bpf/helpers.c:2036:\t\t/ skb and xdp dynptrs should use bpf_dynptr_slice / bpf_dynptr_slice_rdwr /\nkernel/bpf/helpers.c-2037-\t\treturn 0;\nkernel/bpf/helpers.c-2038-\tdefault:\nkernel/bpf/helpers.c:2039:\t\tWARN_ONCE(true, \"bpf_dynptr_data: unknown dynptr type %d\\n\", type);\nkernel/bpf/helpers.c-2040-\t\treturn 0;\n--\nkernel/bpf/helpers.c-2043-\nkernel/bpf/helpers.c:2044:static const struct bpf_func_proto bpf_dynptr_data_proto = {\nkernel/bpf/helpers.c:2045:\t.func\t\t= bpf_dynptr_data,\nkernel/bpf/helpers.c-2046-\t.gpl_only\t= false,\n--\nkernel/bpf/helpers.c=2068=bpf_base_func_proto(enum bpf_func_id func_id, const struct bpf_prog prog)\n--\nkernel/bpf/helpers.c-2161-\tcase BPF_FUNC_dynptr_from_mem:\nkernel/bpf/helpers.c:2162:\t\treturn \u0026bpf_dynptr_from_mem_proto;\nkernel/bpf/helpers.c-2163-\tcase BPF_FUNC_dynptr_read:\nkernel/bpf/helpers.c:2164:\t\treturn \u0026bpf_dynptr_read_proto;\nkernel/bpf/helpers.c-2165-\tcase BPF_FUNC_dynptr_write:\nkernel/bpf/helpers.c:2166:\t\treturn \u0026bpf_dynptr_write_proto;\nkernel/bpf/helpers.c-2167-\tcase BPF_FUNC_dynptr_data:\nkernel/bpf/helpers.c:2168:\t\treturn \u0026bpf_dynptr_data_proto;\nkernel/bpf/helpers.c-2169-#ifdef CONFIG_CGROUPS\n--\nkernel/bpf/helpers.c=3009=__bpf_kfunc struct task_struct bpf_task_from_vpid(s32 vpid)\n--\nkernel/bpf/helpers.c-3024-/\nkernel/bpf/helpers.c:3025: bpf_dynptr_slice() - Obtain a read-only pointer to the dynptr data.\nkernel/bpf/helpers.c-3026- * @p: The dynptr whose data slice to retrieve\n--\nkernel/bpf/helpers.c-3032- * For non-skb and non-xdp type dynptrs, there is no difference between\nkernel/bpf/helpers.c:3033: * bpf_dynptr_slice and bpf_dynptr_data.\nkernel/bpf/helpers.c-3034- \n--\nkernel/bpf/helpers.c-3037- If the intention is to write to the data slice, please use\nkernel/bpf/helpers.c:3038: * bpf_dynptr_slice_rdwr.\nkernel/bpf/helpers.c-3039- \n--\nkernel/bpf/helpers.c-3041- \nkernel/bpf/helpers.c:3042: * Please note that in the case of skb and xdp dynptrs, bpf_dynptr_slice\nkernel/bpf/helpers.c-3043- * does not change the underlying packet data pointers, so a call to\nkernel/bpf/helpers.c:3044: * bpf_dynptr_slice will not invalidate any ctx-\u003edata/data_end pointers in\nkernel/bpf/helpers.c-3045- * the bpf program.\n--\nkernel/bpf/helpers.c-3051- /\nkernel/bpf/helpers.c:3052:__bpf_kfunc void bpf_dynptr_slice(const struct bpf_dynptr p, u64 offset,\nkernel/bpf/helpers.c-3053-\t\t\t\t void buffer__nullable, u64 buffer__szk)\nkernel/bpf/helpers.c-3054-{\nkernel/bpf/helpers.c:3055:\tconst struct bpf_dynptr_kern ptr = (struct bpf_dynptr_kern )p;\nkernel/bpf/helpers.c:3056:\tenum bpf_dynptr_type type;\nkernel/bpf/helpers.c-3057-\tu64 len = buffer__szk;\n--\nkernel/bpf/helpers.c-3062-\nkernel/bpf/helpers.c:3063:\terr = bpf_dynptr_check_off_len(ptr, offset, len);\nkernel/bpf/helpers.c-3064-\tif (err)\n--\nkernel/bpf/helpers.c-3066-\nkernel/bpf/helpers.c:3067:\ttype = bpf_dynptr_get_type(ptr);\nkernel/bpf/helpers.c-3068-\n--\nkernel/bpf/helpers.c-3100-/*\nkernel/bpf/helpers.c:3101: bpf_dynptr_slice_rdwr() - Obtain a writable pointer to the dynptr data.\nkernel/bpf/helpers.c-3102- * @p: The dynptr whose data slice to retrieve\n--\nkernel/bpf/helpers.c-3108- * For non-skb and non-xdp type dynptrs, there is no difference between\nkernel/bpf/helpers.c:3109: * bpf_dynptr_slice and bpf_dynptr_data.\nkernel/bpf/helpers.c-3110- \n--\nkernel/bpf/helpers.c-3116- packet). In the case where the returned pointer is to the buffer, the user\nkernel/bpf/helpers.c:3117: * is responsible for persisting writes through calling bpf_dynptr_write(). This\nkernel/bpf/helpers.c-3118- * usually looks something like this pattern:\nkernel/bpf/helpers.c-3119- \nkernel/bpf/helpers.c:3120: struct eth_hdr eth = bpf_dynptr_slice_rdwr(\u0026dynptr, 0, buffer, sizeof(buffer));\nkernel/bpf/helpers.c-3121- if (!eth)\n--\nkernel/bpf/helpers.c-3126- * if (eth == buffer)\nkernel/bpf/helpers.c:3127: \tbpf_dynptr_write(\u0026ptr, 0, buffer, sizeof(buffer), 0);\nkernel/bpf/helpers.c-3128- \n--\nkernel/bpf/helpers.c-3131- \nkernel/bpf/helpers.c:3132: Please also note that in the case of skb and xdp dynptrs, bpf_dynptr_slice_rdwr\nkernel/bpf/helpers.c-3133- * does not change the underlying packet data pointers, so a call to\nkernel/bpf/helpers.c:3134: * bpf_dynptr_slice_rdwr will not invalidate any ctx-\u003edata/data_end pointers in\nkernel/bpf/helpers.c-3135- * the bpf program.\n--\nkernel/bpf/helpers.c-3141- /\nkernel/bpf/helpers.c:3142:__bpf_kfunc void bpf_dynptr_slice_rdwr(const struct bpf_dynptr p, u64 offset,\nkernel/bpf/helpers.c-3143-\t\t\t\t\tvoid buffer__nullable, u64 buffer__szk)\nkernel/bpf/helpers.c-3144-{\nkernel/bpf/helpers.c:3145:\tconst struct bpf_dynptr_kern ptr = (struct bpf_dynptr_kern )p;\nkernel/bpf/helpers.c-3146-\nkernel/bpf/helpers.c:3147:\tif (!ptr-\u003edata \|\| __bpf_dynptr_is_rdonly(ptr))\nkernel/bpf/helpers.c-3148-\t\treturn NULL;\nkernel/bpf/helpers.c-3149-\nkernel/bpf/helpers.c:3150:\t/* bpf_dynptr_slice_rdwr is the same logic as bpf_dynptr_slice.\nkernel/bpf/helpers.c-3151-\t \n--\nkernel/bpf/helpers.c-3153-\t if the bpf program allows skb data writes. There are two possibilities\nkernel/bpf/helpers.c:3154:\t * that may occur when calling bpf_dynptr_slice_rdwr:\nkernel/bpf/helpers.c-3155-\t \n--\nkernel/bpf/helpers.c-3164-\t will not be pulled. To persist the write, the user will need to call\nkernel/bpf/helpers.c:3165:\t * bpf_dynptr_write(), which will pull the skb and commit the write.\nkernel/bpf/helpers.c-3166-\t \n--\nkernel/bpf/helpers.c-3169-\t will be copied out into the buffer and the user will need to call\nkernel/bpf/helpers.c:3170:\t * bpf_dynptr_write() to commit changes.\nkernel/bpf/helpers.c-3171-\t /\nkernel/bpf/helpers.c:3172:\treturn bpf_dynptr_slice(p, offset, buffer__nullable, buffer__szk);\nkernel/bpf/helpers.c-3173-}\nkernel/bpf/helpers.c-3174-\nkernel/bpf/helpers.c:3175:__bpf_kfunc int bpf_dynptr_adjust(struct bpf_dynptr p, u64 start, u64 end)\nkernel/bpf/helpers.c-3176-{\nkernel/bpf/helpers.c:3177:\tstruct bpf_dynptr_kern ptr = (struct bpf_dynptr_kern )p;\nkernel/bpf/helpers.c-3178-\tu64 size;\n--\nkernel/bpf/helpers.c-3182-\nkernel/bpf/helpers.c:3183:\tsize = __bpf_dynptr_size(ptr);\nkernel/bpf/helpers.c-3184-\n--\nkernel/bpf/helpers.c-3187-\nkernel/bpf/helpers.c:3188:\tbpf_dynptr_advance_offset(ptr, start);\nkernel/bpf/helpers.c:3189:\tbpf_dynptr_set_size(ptr, end - start);\nkernel/bpf/helpers.c-3190-\n--\nkernel/bpf/helpers.c-3193-\nkernel/bpf/helpers.c:3194:__bpf_kfunc bool bpf_dynptr_is_null(const struct bpf_dynptr p)\nkernel/bpf/helpers.c-3195-{\nkernel/bpf/helpers.c:3196:\tconst struct bpf_dynptr_kern ptr = (struct bpf_dynptr_kern )p;\nkernel/bpf/helpers.c-3197-\n--\nkernel/bpf/helpers.c-3200-\nkernel/bpf/helpers.c:3201:__bpf_kfunc bool bpf_dynptr_is_rdonly(const struct bpf_dynptr p)\nkernel/bpf/helpers.c-3202-{\nkernel/bpf/helpers.c:3203:\tconst struct bpf_dynptr_kern ptr = (struct bpf_dynptr_kern )p;\nkernel/bpf/helpers.c-3204-\n--\nkernel/bpf/helpers.c-3207-\nkernel/bpf/helpers.c:3208:\treturn __bpf_dynptr_is_rdonly(ptr);\nkernel/bpf/helpers.c-3209-}\nkernel/bpf/helpers.c-3210-\nkernel/bpf/helpers.c:3211:__bpf_kfunc u64 bpf_dynptr_size(const struct bpf_dynptr p)\nkernel/bpf/helpers.c-3212-{\nkernel/bpf/helpers.c:3213:\tconst struct bpf_dynptr_kern ptr = (struct bpf_dynptr_kern )p;\nkernel/bpf/helpers.c-3214-\n--\nkernel/bpf/helpers.c-3217-\nkernel/bpf/helpers.c:3218:\treturn __bpf_dynptr_size(ptr);\nkernel/bpf/helpers.c-3219-}\nkernel/bpf/helpers.c-3220-\nkernel/bpf/helpers.c:3221:__bpf_kfunc int bpf_dynptr_clone(const struct bpf_dynptr p,\nkernel/bpf/helpers.c-3222-\t\t\t\t struct bpf_dynptr clone__uninit)\nkernel/bpf/helpers.c-3223-{\nkernel/bpf/helpers.c:3224:\tstruct bpf_dynptr_kern clone = (struct bpf_dynptr_kern )clone__uninit;\nkernel/bpf/helpers.c:3225:\tconst struct bpf_dynptr_kern ptr = (struct bpf_dynptr_kern )p;\nkernel/bpf/helpers.c-3226-\nkernel/bpf/helpers.c-3227-\tif (!ptr-\u003edata) {\nkernel/bpf/helpers.c:3228:\t\tbpf_dynptr_set_null(clone);\nkernel/bpf/helpers.c-3229-\t\treturn -EINVAL;\n--\nkernel/bpf/helpers.c-3237-/\nkernel/bpf/helpers.c:3238: bpf_dynptr_copy() - Copy data from one dynptr to another.\nkernel/bpf/helpers.c-3239- * @dst_ptr: Destination dynptr - where data should be copied to\n--\nkernel/bpf/helpers.c-3247- /\nkernel/bpf/helpers.c:3248:__bpf_kfunc int bpf_dynptr_copy(const struct bpf_dynptr dst_ptr, u64 dst_off,\nkernel/bpf/helpers.c-3249-\t\t\t\tconst struct bpf_dynptr src_ptr, u64 src_off, u64 size)\nkernel/bpf/helpers.c-3250-{\nkernel/bpf/helpers.c:3251:\tconst struct bpf_dynptr_kern dst = (struct bpf_dynptr_kern )dst_ptr;\nkernel/bpf/helpers.c:3252:\tconst struct bpf_dynptr_kern src = (struct bpf_dynptr_kern )src_ptr;\nkernel/bpf/helpers.c-3253-\tvoid src_slice, dst_slice;\n--\nkernel/bpf/helpers.c-3256-\nkernel/bpf/helpers.c:3257:\tsrc_slice = bpf_dynptr_slice(src_ptr, src_off, NULL, size);\nkernel/bpf/helpers.c:3258:\tdst_slice = bpf_dynptr_slice_rdwr(dst_ptr, dst_off, NULL, size);\nkernel/bpf/helpers.c-3259-\n--\nkernel/bpf/helpers.c-3265-\tif (src_slice)\nkernel/bpf/helpers.c:3266:\t\treturn __bpf_dynptr_write(dst, dst_off, src_slice, size, 0);\nkernel/bpf/helpers.c-3267-\nkernel/bpf/helpers.c-3268-\tif (dst_slice)\nkernel/bpf/helpers.c:3269:\t\treturn __bpf_dynptr_read(dst_slice, size, src, src_off, 0);\nkernel/bpf/helpers.c-3270-\nkernel/bpf/helpers.c:3271:\tif (bpf_dynptr_check_off_len(dst, dst_off, size) \|\|\nkernel/bpf/helpers.c:3272:\t bpf_dynptr_check_off_len(src, src_off, size))\nkernel/bpf/helpers.c-3273-\t\treturn -E2BIG;\n--\nkernel/bpf/helpers.c-3279-\nkernel/bpf/helpers.c:3280:\t\terr = __bpf_dynptr_read(buf, chunk_sz, src, src_off + off, 0);\nkernel/bpf/helpers.c-3281-\t\tif (err)\nkernel/bpf/helpers.c-3282-\t\t\treturn err;\nkernel/bpf/helpers.c:3283:\t\terr = __bpf_dynptr_write(dst, dst_off + off, buf, chunk_sz, 0);\nkernel/bpf/helpers.c-3284-\t\tif (err)\n--\nkernel/bpf/helpers.c-3292-/\nkernel/bpf/helpers.c:3293: bpf_dynptr_memset() - Fill dynptr memory with a constant byte.\nkernel/bpf/helpers.c-3294- * @p: Destination dynptr - where data will be filled\n--\nkernel/bpf/helpers.c-3302- /\nkernel/bpf/helpers.c:3303:__bpf_kfunc int bpf_dynptr_memset(const struct bpf_dynptr p, u64 offset, u64 size, u8 val)\nkernel/bpf/helpers.c-3304-{\nkernel/bpf/helpers.c:3305:\tconst struct bpf_dynptr_kern ptr = (struct bpf_dynptr_kern )p;\nkernel/bpf/helpers.c-3306-\tu64 chunk_sz, write_off;\n--\nkernel/bpf/helpers.c-3310-\nkernel/bpf/helpers.c:3311:\tslice = bpf_dynptr_slice_rdwr(p, offset, NULL, size);\nkernel/bpf/helpers.c-3312-\tif (likely(slice)) {\n--\nkernel/bpf/helpers.c-3316-\nkernel/bpf/helpers.c:3317:\tif (__bpf_dynptr_is_rdonly(ptr))\nkernel/bpf/helpers.c-3318-\t\treturn -EINVAL;\nkernel/bpf/helpers.c-3319-\nkernel/bpf/helpers.c:3320:\terr = bpf_dynptr_check_off_len(ptr, offset, size);\nkernel/bpf/helpers.c-3321-\tif (err)\n--\nkernel/bpf/helpers.c-3329-\t\tchunk_sz = min_t(u64, sizeof(buf), size - write_off);\nkernel/bpf/helpers.c:3330:\t\terr = __bpf_dynptr_write(ptr, offset + write_off, buf, chunk_sz, 0);\nkernel/bpf/helpers.c-3331-\t\tif (err)\n--\nkernel/bpf/helpers.c=4319=__bpf_kfunc int bpf_verify_pkcs7_signature(const struct bpf_dynptr data_p,\n--\nkernel/bpf/helpers.c-4323-#ifdef CONFIG_SYSTEM_DATA_VERIFICATION\nkernel/bpf/helpers.c:4324:\tconst struct bpf_dynptr_kern data_ptr = (struct bpf_dynptr_kern )data_p;\nkernel/bpf/helpers.c:4325:\tconst struct bpf_dynptr_kern sig_ptr = (struct bpf_dynptr_kern )sig_p;\nkernel/bpf/helpers.c-4326-\tconst void data, sig;\n--\nkernel/bpf/helpers.c-4343-\nkernel/bpf/helpers.c:4344:\tdata_len = __bpf_dynptr_size(data_ptr);\nkernel/bpf/helpers.c:4345:\tdata = __bpf_dynptr_data(data_ptr, data_len);\nkernel/bpf/helpers.c-4346-\tif (!data)\n--\nkernel/bpf/helpers.c-4348-\nkernel/bpf/helpers.c:4349:\tsig_len = __bpf_dynptr_size(sig_ptr);\nkernel/bpf/helpers.c:4350:\tsig = __bpf_dynptr_data(sig_ptr, sig_len);\nkernel/bpf/helpers.c-4351-\tif (!sig)\n--\nkernel/bpf/helpers.c=4680=static int make_file_dynptr(struct file file, u32 flags, bool may_sleep,\nkernel/bpf/helpers.c:4681:\t\t\t struct bpf_dynptr_kern ptr)\nkernel/bpf/helpers.c-4682-{\nkernel/bpf/helpers.c:4683:\tstruct bpf_dynptr_file_impl state;\nkernel/bpf/helpers.c-4684-\n--\nkernel/bpf/helpers.c-4686-\tif (flags) {\nkernel/bpf/helpers.c:4687:\t\tbpf_dynptr_set_null(ptr);\nkernel/bpf/helpers.c-4688-\t\treturn -EINVAL;\n--\nkernel/bpf/helpers.c-4692-\tif (!state) {\nkernel/bpf/helpers.c:4693:\t\tbpf_dynptr_set_null(ptr);\nkernel/bpf/helpers.c-4694-\t\treturn -ENOMEM;\n--\nkernel/bpf/helpers.c-4698-\tfreader_init_from_file(\u0026state-\u003efreader, NULL, 0, file, may_sleep);\nkernel/bpf/helpers.c:4699:\tbpf_dynptr_init(ptr, state, BPF_DYNPTR_TYPE_FILE, 0, 0);\nkernel/bpf/helpers.c:4700:\tbpf_dynptr_set_rdonly(ptr);\nkernel/bpf/helpers.c-4701-\treturn 0;\n--\nkernel/bpf/helpers.c-4703-\nkernel/bpf/helpers.c:4704:__bpf_kfunc int bpf_dynptr_from_file(struct file file, u32 flags, struct bpf_dynptr ptr__uninit)\nkernel/bpf/helpers.c-4705-{\nkernel/bpf/helpers.c:4706:\treturn make_file_dynptr(file, flags, false, (struct bpf_dynptr_kern )ptr__uninit);\nkernel/bpf/helpers.c-4707-}\nkernel/bpf/helpers.c-4708-\nkernel/bpf/helpers.c:4709:int bpf_dynptr_from_file_sleepable(struct file file, u32 flags, struct bpf_dynptr ptr__uninit)\nkernel/bpf/helpers.c-4710-{\nkernel/bpf/helpers.c:4711:\treturn make_file_dynptr(file, flags, true, (struct bpf_dynptr_kern )ptr__uninit);\nkernel/bpf/helpers.c-4712-}\nkernel/bpf/helpers.c-4713-\nkernel/bpf/helpers.c:4714:__bpf_kfunc int bpf_dynptr_file_discard(struct bpf_dynptr dynptr)\nkernel/bpf/helpers.c-4715-{\nkernel/bpf/helpers.c:4716:\tstruct bpf_dynptr_kern ptr = (struct bpf_dynptr_kern )dynptr;\nkernel/bpf/helpers.c:4717:\tstruct bpf_dynptr_file_impl df = ptr-\u003edata;\nkernel/bpf/helpers.c-4718-\n--\nkernel/bpf/helpers.c-4723-\tkfree_nolock(df);\nkernel/bpf/helpers.c:4724:\tbpf_dynptr_set_null(ptr);\nkernel/bpf/helpers.c-4725-\treturn 0;\n--\nkernel/bpf/helpers.c=4889=BTF_ID_FLAGS(func, bpf_rcu_read_unlock)\nkernel/bpf/helpers.c:4890:BTF_ID_FLAGS(func, bpf_dynptr_slice, KF_RET_NULL)\nkernel/bpf/helpers.c:4891:BTF_ID_FLAGS(func, bpf_dynptr_slice_rdwr, KF_RET_NULL)\nkernel/bpf/helpers.c-4892-BTF_ID_FLAGS(func, bpf_iter_num_new, KF_ITER_NEW \| KF_SPINLOCK_SAFE)\n--\nkernel/bpf/helpers.c=4908=BTF_ID_FLAGS(func, bpf_iter_task_destroy, KF_ITER_DESTROY)\nkernel/bpf/helpers.c:4909:BTF_ID_FLAGS(func, bpf_dynptr_adjust)\n\n" }
21/2	2026/09/18 20:58	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 29372 output: 223 thoughts: 928 Thoughts: Dynptr Cleanup on Function Exit: A BPF Verifier Perspective Okay, so I've been digging into how dynptrs are handled, specifically focusing on their lifecycle within BPF programs. It seems these `dynptrs`, which are standard BPF features defined in `helpers.c` and `verifier.c`, are controlled by `CONFIG_BPF_SYSCALL` (which is selected by `CONFIG_BPF`). I checked around, and while some features like `bpf_dynptr_from_skb` might indirectly depend on `CONFIG_NET` (as seen in selftests), the core functionality for ringbuf and general dynptrs (`bpf_dynptr_from_mem`, `bpf_ringbuf_reserve_dynptr`) fundamentally relies on `BPF_SYSCALL`. So, that's our key configuration. Now, let's nail down the critical symbols. I'm seeing a cluster of functions that seem pivotal for tracking and cleaning up these dynptrs: `destroy_dynptrs_on_func_exit`, `destroy_if_dynptr_stack_slot`, and `prepare_func_exit`. I re-examined the git diffs in `kernel/bpf/verifier.c` and found additional related functions like `mark_stack_slots_dynptr`, `check_stack_write_fixed_off`, and `check_stack_write_var_off`. Specifically, `prepare_func_exit` calls `destroy_dynptrs_on_func_exit`, which iterates through callee stack slots and calls `destroy_if_dynptr_stack_slot(..., on_func_exit=true)`. This inner function checks if it's on function exit and if the dynptr is referenced and its reference count is less than or equal to 1. These are all pretty specific to how the BPF verifier handles dynptr destruction and verification related to function return. They're not some generic low-level memory management hot-path. Let's summarize the key symbols for the 'set-results' stage: I should include: `destroy_dynptrs_on_func_exit`, `destroy_if_dynptr_stack_slot`, `prepare_func_exit`, and `mark_stack_slots_dynptr`, as well as `process_bpf_exit_full`, because it's the handler for `BPF_EXIT`, which is where function exits are handled during verification. For the required parameters, the `WorthFuzzing` flag should be set to true. The reasoning is that the patch modifies the BPF verifier, specifically, it adds logic to track and properly clean up callee-local dynptrs when a function exits (using `destroy_dynptrs_on_func_exit`). This prevents dynptrs referenced within a subprogram or callback from leaking on exit and ensures derived slices are invalidated correctly. It's important because this all touches core BPF verification logic, reachable via `bpf(BPF_PROG_LOAD)`. The focus symbols are: `destroy_dynptrs_on_func_exit`, `destroy_if_dynptr_stack_slot`, `prepare_func_exit`, `process_bpf_exit_full`, and `mark_stack_slots_dynptr`. The necessary config is `BPF_SYSCALL`. Alright, I'm confident I've got this covered.
22/2	2026/09/18 20:58	tool	set-results	0m Args: { "EnableConfigs": [ "BPF_SYSCALL" ], "FocusSymbols": [ "destroy_dynptrs_on_func_exit", "destroy_if_dynptr_stack_slot", "prepare_func_exit", "process_bpf_exit_full", "mark_stack_slots_dynptr" ], "Reasoning": "The patch modifies core BPF verifier logic in kernel/bpf/verifier.c by adding teardown of callee-local dynptrs on function return (destroy_dynptrs_on_func_exit) called from prepare_func_exit(). It invalidates slices derived from local dynptrs and rejects returns when the last dynptr holding a referenced resource is about to be lost. This is fully reachable from userspace via the bpf() syscall (BPF_PROG_LOAD) and warrants fuzzing for verifier state tracking bugs, pruning regressions, or false verifier rejections/acceptances.", "WorthFuzzing": true } Results: { "EnableConfigs": [ "BPF_SYSCALL" ], "FocusSymbols": [ "destroy_dynptrs_on_func_exit", "destroy_if_dynptr_stack_slot", "prepare_func_exit", "process_bpf_exit_full", "mark_stack_slots_dynptr" ], "Reasoning": "The patch modifies core BPF verifier logic in kernel/bpf/verifier.c by adding teardown of callee-local dynptrs on function return (destroy_dynptrs_on_func_exit) called from prepare_func_exit(). It invalidates slices derived from local dynptrs and rejects returns when the last dynptr holding a referenced resource is about to be lost. This is fully reachable from userspace via the bpf() syscall (BPF_PROG_LOAD) and warrants fuzzing for verifier state tracking bugs, pruning regressions, or false verifier rejections/acceptances.", "WorthFuzzing": true }
23/1	2026/09/18 20:58	action	If	0m Args: { "WorthFuzzing": true } Results: null
24/2	2026/09/18 20:58	agent	kmsan-evaluator	0m Model: core Args: null Results: { "KMSANReasoning": "The patch modifies the BPF verifier (kernel/bpf/verifier.c) to tear down local dynptrs and invalidate derived slices when returning from a BPF subprogram (prepare_func_exit). It also adds a check ensuring that departing stack frames cannot drop the last dynptr referencing a resource.\n\nFrom a memory safety perspective:\n1. The bug being addressed relates to stale slices and reference tracking across stack frames, which at runtime in BPF programs could lead to use-after-free or dangling pointer dereferences. These memory corruption bugs are caught by standard KASAN, not KMSAN.\n2. The patch touches only static verifier verification state logic and selftests. No kernel-to-userspace copies (info-leaks), uninitialized stack/heap allocations, or branches on uninitialized memory are introduced or exposed. All variables in the new verifier functions are fully initialized.\n\nTherefore, this change does not introduce or expose uninitialized memory risks, 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 d38f515d2bf5529abf4e8907d23dee8c7e4074a4 Author: syz-cluster <triage@syzkaller.com> Date: Fri Sep 18 20:57:25 2026 +0000 syz-cluster: applied patch under review diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 6c6b8d8520cdf..4beca102c11d1 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -709,7 +709,8 @@ static void mark_dynptr_cb_reg(struct bpf_verifier_env env, } static int destroy_if_dynptr_stack_slot(struct bpf_verifier_env env, - struct bpf_func_state state, int spi); + struct bpf_func_state state, int spi, + bool on_func_exit); static int mark_stack_slots_dynptr(struct bpf_verifier_env env, struct bpf_reg_state reg, enum bpf_arg_type arg_type, int insn_idx, @@ -732,10 +733,10 @@ static int mark_stack_slots_dynptr(struct bpf_verifier_env env, struct bpf_reg_ case they do belong to same dynptr, second call won't see slot_type * as STACK_DYNPTR and will simply skip destruction. / - err = destroy_if_dynptr_stack_slot(env, state, spi); + err = destroy_if_dynptr_stack_slot(env, state, spi, false); if (err) return err; - err = destroy_if_dynptr_stack_slot(env, state, spi - 1); + err = destroy_if_dynptr_stack_slot(env, state, spi - 1, false); if (err) return err; @@ -843,8 +844,34 @@ static int dynptr_ref_cnt(struct bpf_verifier_env env, int v_parent_id) return ref_cnt; } +static int destroy_dynptrs_on_func_exit(struct bpf_verifier_env env, + struct bpf_func_state callee) +{ + int i, err; + + for (i = 0; i < callee->allocated_stack / BPF_REG_SIZE; i++) { + struct bpf_stack_state slot = &callee->stack[i]; + + if (slot->slot_type[0] != STACK_DYNPTR \|\| + !slot->spilled_ptr.dynptr.first_slot) + continue; + + / + * A callee-local dynptr is destroyed when its stack frame goes + * away. Apply the normal stack-slot teardown so references cannot + * be lost and slices derived from that dynptr are invalidated. + / + err = destroy_if_dynptr_stack_slot(env, callee, i, true); + if (err) + return err; + } + + return 0; +} + static int destroy_if_dynptr_stack_slot(struct bpf_verifier_env env, - struct bpf_func_state state, int spi) + struct bpf_func_state state, int spi, + bool on_func_exit) { int err = 0; @@ -867,6 +894,15 @@ static int destroy_if_dynptr_stack_slot(struct bpf_verifier_env env, / if (dynptr_type_referenced(state->stack[spi].spilled_ptr.dynptr.type) && dynptr_ref_cnt(env, state->stack[spi].spilled_ptr.parent_id) <= 1) { + if (on_func_exit) { + verbose(env, "cannot return with referenced dynptr in callee stack\n"); + bpf_diag_res(env, env->insn_idx, + "referenced dynptr on function return", + "The departing stack frame contains the last dynptr that can release a referenced resource.", + "Release the referenced resource before returning from this function."); + return -EINVAL; + } + verbose(env, "cannot overwrite referenced dynptr\n"); bpf_diag_res( env, env->insn_idx, "referenced dynptr overwrite", @@ -3630,7 +3666,7 @@ static int check_stack_write_fixed_off(struct bpf_verifier_env env, env->insn_aux_data[insn_idx].nospec_result = true; } - err = destroy_if_dynptr_stack_slot(env, state, spi); + err = destroy_if_dynptr_stack_slot(env, state, spi, false); if (err) return err; @@ -3750,7 +3786,7 @@ static int check_stack_write_var_off(struct bpf_verifier_env env, int spi; spi = bpf_get_spi(i); - err = destroy_if_dynptr_stack_slot(env, state, spi); + err = destroy_if_dynptr_stack_slot(env, state, spi, false); if (err) return err; } @@ -11043,6 +11079,9 @@ static int prepare_func_exit(struct bpf_verifier_env env, int insn_idx) bpf_diag_mod_end(env); } } + err = destroy_dynptrs_on_func_exit(env, callee); + if (err) + return err; /* for callbacks like bpf_loop or bpf_for_each_map_elem go back to callsite, * there function call logic would reschedule callback visit. If iteration diff --git a/tools/testing/selftests/bpf/prog_tests/bpf_qdisc.c b/tools/testing/selftests/bpf/prog_tests/bpf_qdisc.c index 6dbd1487343c0..122ecb7e98e2a 100644 --- a/tools/testing/selftests/bpf/prog_tests/bpf_qdisc.c +++ b/tools/testing/selftests/bpf/prog_tests/bpf_qdisc.c @@ -11,6 +11,7 @@ #include "bpf_qdisc_fail__invalid_dynptr.skel.h" #include "bpf_qdisc_fail__invalid_dynptr_slice.skel.h" #include "bpf_qdisc_fail__invalid_dynptr_cross_frame.skel.h" +#include "bpf_qdisc_fail__invalid_dynptr_returned_slice.skel.h" #include "bpf_qdisc_fail__untrusted_write.skel.h" #include "bpf_qdisc_dynptr_use_after_invalidate_clone.skel.h" @@ -230,6 +231,7 @@ void test_ns_bpf_qdisc(void) test_incompl_ops(); RUN_TESTS(bpf_qdisc_fail__invalid_dynptr); RUN_TESTS(bpf_qdisc_fail__invalid_dynptr_cross_frame); + RUN_TESTS(bpf_qdisc_fail__invalid_dynptr_returned_slice); RUN_TESTS(bpf_qdisc_fail__invalid_dynptr_slice); RUN_TESTS(bpf_qdisc_fail__untrusted_write); RUN_TESTS(bpf_qdisc_dynptr_use_after_invalidate_clone); diff --git a/tools/testing/selftests/bpf/progs/bpf_qdisc_fail__invalid_dynptr_returned_slice.c b/tools/testing/selftests/bpf/progs/bpf_qdisc_fail__invalid_dynptr_returned_slice.c new file mode 100644 index 0000000000000..8217f4c4c00c4 --- /dev/null +++ b/tools/testing/selftests/bpf/progs/bpf_qdisc_fail__invalid_dynptr_returned_slice.c @@ -0,0 +1,76 @@ +// SPDX-License-Identifier: GPL-2.0 + +#include <vmlinux.h> +#include "bpf_experimental.h" +#include "bpf_qdisc_common.h" +#include "bpf_misc.h" + +char _license[] SEC("license") = "GPL"; + +int proto; + +static __noinline struct ethhdr slice_in_subprog(struct sk_buff skb) +{ + struct bpf_dynptr ptr; + + bpf_dynptr_from_skb((struct __sk_buff )skb, 0, &ptr); + return bpf_dynptr_slice(&ptr, 0, NULL, sizeof(struct ethhdr)); +} + +SEC("struct_ops") +__failure __msg("invalid mem access 'scalar'") +int BPF_PROG(invalid_dynptr_returned_slice, struct sk_buff skb, + struct Qdisc sch, struct bpf_sk_buff_ptr to_free) +{ + struct ethhdr hdr; + + hdr = slice_in_subprog(skb); + if (!hdr) { + bpf_qdisc_skb_drop(skb, to_free); + return NET_XMIT_DROP; + } + + / this should fail / + proto = hdr->h_proto; + + bpf_qdisc_skb_drop(skb, to_free); + + return NET_XMIT_DROP; +} + +SEC("struct_ops") +__auxiliary +struct sk_buff BPF_PROG(bpf_qdisc_test_dequeue, struct Qdisc sch) +{ + return NULL; +} + +SEC("struct_ops") +__auxiliary +int BPF_PROG(bpf_qdisc_test_init, struct Qdisc sch, struct nlattr opt, + struct netlink_ext_ack extack) +{ + return 0; +} + +SEC("struct_ops") +__auxiliary +void BPF_PROG(bpf_qdisc_test_reset, struct Qdisc sch) +{ +} + +SEC("struct_ops") +__auxiliary +void BPF_PROG(bpf_qdisc_test_destroy, struct Qdisc sch) +{ +} + +SEC(".struct_ops") +struct Qdisc_ops test = { + .enqueue = (void )invalid_dynptr_returned_slice, + .dequeue = (void )bpf_qdisc_test_dequeue, + .init = (void )bpf_qdisc_test_init, + .reset = (void )bpf_qdisc_test_reset, + .destroy = (void )bpf_qdisc_test_destroy, + .id = "bpf_qdisc_test", +}; diff --git a/tools/testing/selftests/bpf/progs/dynptr_fail.c b/tools/testing/selftests/bpf/progs/dynptr_fail.c index 1cd61d72c166f..aed18403ae3c0 100644 --- a/tools/testing/selftests/bpf/progs/dynptr_fail.c +++ b/tools/testing/selftests/bpf/progs/dynptr_fail.c @@ -125,9 +125,9 @@ static int missing_release_callback_fn(__u32 index, void data) return 0; } -/* Any dynptr initialized within a callback must have bpf_dynptr_put called / +/ A callback cannot return with the last dynptr for a referenced resource. / SEC("?raw_tp") -__failure __msg("Unreleased reference id") +__failure __msg("cannot return with referenced dynptr") int ringbuf_missing_release_callback(void ctx) { bpf_loop(10, missing_release_callback_fn, NULL, 0); @@ -1892,6 +1892,101 @@ int clone_invalidate4(void ctx) return 0; } +static __noinline void clone_slice_in_subprog(struct bpf_dynptr ptr, int *data) +{ + struct bpf_dynptr clone; + + bpf_dynptr_clone(ptr, &clone); + data = bpf_dynptr_data(&clone, 0, sizeof(val)); +} + +static __noinline void caller_slice_in_subprog(struct bpf_dynptr ptr, int data) +{ + struct bpf_dynptr clone; + + data = bpf_dynptr_data(ptr, 0, sizeof(val)); + bpf_dynptr_clone(ptr, &clone); +} + +static __noinline void reserve_dynptr_in_subprog(void) +{ + struct bpf_dynptr ptr; + + bpf_ringbuf_reserve_dynptr(&ringbuf, val, 0, &ptr); +} + +/* A subprogram cannot lose the last dynptr that can release a resource. / +SEC("?raw_tp") +__failure __msg("cannot return with referenced dynptr") +int referenced_dynptr_lost_on_subprog_return(void ctx) +{ + reserve_dynptr_in_subprog(); + + return 0; +} + +/* + * Destroying a local clone on return must not invalidate a slice whose + * source dynptr belongs to the caller. + / +SEC("?raw_tp") +__success +int caller_dynptr_slice_across_subprog_valid(void ctx) +{ + struct bpf_dynptr ptr; + int data = NULL; + + bpf_ringbuf_reserve_dynptr(&ringbuf, val, 0, &ptr); + caller_slice_in_subprog(&ptr, &data); + if (data) + data = 123; + bpf_ringbuf_submit_dynptr(&ptr, 0); + + return 0; +} + +/* + * A slice that escapes a clone's call frame is invalid once the local + * clone is destroyed on return. + / +SEC("?raw_tp") +__failure __msg("invalid mem access 'scalar'") +int clone_slice_returned_frame_invalid(void ctx) +{ + struct bpf_dynptr ptr; + int data = NULL; + + bpf_ringbuf_reserve_dynptr(&ringbuf, val, 0, &ptr); + clone_slice_in_subprog(&ptr, &data); + if (data) + / this should fail / + data = 123; + bpf_ringbuf_submit_dynptr(&ptr, 0); + + return 0; +} + +/* + * A slice from a caller-owned dynptr survives the subprogram return, but + * releasing the shared reservation must invalidate it. + / +SEC("?raw_tp") +__failure __msg("invalid mem access 'scalar'") +int caller_dynptr_slice_release_after_subprog_invalid(void ctx) +{ + struct bpf_dynptr ptr; + int data = NULL; + + bpf_ringbuf_reserve_dynptr(&ringbuf, val, 0, &ptr); + caller_slice_in_subprog(&ptr, &data); + bpf_ringbuf_submit_dynptr(&ptr, 0); + if (data) + / this should fail / + data = 123; + + return 0; +} + /* Invalidating a dynptr should invalidate any data slices * of its parent */
25/3	2026/09/18 20:58	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 6036 output: 38 thoughts: 739 Thoughts: Analyzing a BPF Verifier Patch for KMSAN Fuzzing Potential Okay, let's dive into this. The goal is to figure out if this patch to the BPF verifier warrants firing up a KMSAN fuzzing session. I've got to assess the risk of memory safety bugs introduced or, more optimistically, addressed. First, I see the changes touch `kernel/bpf/verifier.c` and some selftests, which is a good starting point. That means there's a good chance it addresses real-world issues. Looking at the code, it looks like a change to how dynptrs (dynamic pointers) are handled in the verifier, specifically around stack slots. The `destroy_if_dynptr_stack_slot` function has been modified, and a new function, `destroy_dynptrs_on_func_exit`, has been added. The addition of a boolean, `on_func_exit`, to the `destroy_if_dynptr_stack_slot` function is immediately interesting. This suggests different handling for dynptrs depending on whether we're leaving a function or not. The new `destroy_dynptrs_on_func_exit` function iterates through a function's allocated stack slots, looking for dynptrs. If it finds one, it calls `destroy_if_dynptr_stack_slot`, with the `on_func_exit` flag set to `true`. Now, the crucial part: inside `destroy_if_dynptr_stack_slot`, there's a conditional check related to referenced dynptrs. If the dynptr is referenced and we're on function exit, it returns an error with a diagnostic message. This is important: it's preventing the return of a function that still has a referenced dynptr in its stack frame. This is likely a bug fix and a good one! This prevents a potential use-after-free or a related memory corruption by ensuring that referenced resources are released before leaving the function. The `prepare_func_exit` function is now calling the `destroy_dynptrs_on_func_exit`, which means that it will attempt to clean up any dynptrs on the stack prior to a function's return. I need to understand what `destroy_if_dynptr_stack_slot` actually does when destroying a dynptr. The logic here could involve invalidating pointers, freeing memory, or a combination of both. I will examine the codebase to investigate the exact implications of the function, since I will want to check that the introduced checks aren't masking a broader vulnerability. Given the nature of the changes – specifically the handling of dynptrs and their lifecycle, and the prevention of exiting a function with references – this patch looks like a good candidate for KMSAN fuzzing. It's addressing potential memory safety issues, and fuzzing could reveal subtle bugs in the implementation, especially in edge cases and during stack unwinding. A dedicated fuzzing session is probably justified, with specific focus on dynptr usage, stack handling, and function exit paths. It looks like a good place to concentrate effort.
26/3	2026/09/18 20:58	tool	grepper	0m Args: { "Expression": "destroy_if_dynptr_stack_slot", "PathPrefix": "kernel/bpf/verifier.c" } Results: { "Output": "kernel/bpf/verifier.c=704=static void mark_dynptr_cb_reg(struct bpf_verifier_env env,\n--\nkernel/bpf/verifier.c-710-\nkernel/bpf/verifier.c:711:static int destroy_if_dynptr_stack_slot(struct bpf_verifier_env env,\nkernel/bpf/verifier.c-712-\t\t\t\t\tstruct bpf_func_state state, int spi,\n--\nkernel/bpf/verifier.c=715=static int mark_stack_slots_dynptr(struct bpf_verifier_env env, struct bpf_reg_state reg,\n--\nkernel/bpf/verifier.c-727-\t/ We cannot assume both spi and spi - 1 belong to the same dynptr,\nkernel/bpf/verifier.c:728:\t * hence we need to call destroy_if_dynptr_stack_slot twice for both,\nkernel/bpf/verifier.c-729-\t * to ensure that for the following example:\n--\nkernel/bpf/verifier.c-735-\t /\nkernel/bpf/verifier.c:736:\terr = destroy_if_dynptr_stack_slot(env, state, spi, false);\nkernel/bpf/verifier.c-737-\tif (err)\nkernel/bpf/verifier.c-738-\t\treturn err;\nkernel/bpf/verifier.c:739:\terr = destroy_if_dynptr_stack_slot(env, state, spi - 1, false);\nkernel/bpf/verifier.c-740-\tif (err)\n--\nkernel/bpf/verifier.c=847=static int destroy_dynptrs_on_func_exit(struct bpf_verifier_env env,\n--\nkernel/bpf/verifier.c-863-\t\t /\nkernel/bpf/verifier.c:864:\t\terr = destroy_if_dynptr_stack_slot(env, callee, i, true);\nkernel/bpf/verifier.c-865-\t\tif (err)\n--\nkernel/bpf/verifier.c-871-\nkernel/bpf/verifier.c:872:static int destroy_if_dynptr_stack_slot(struct bpf_verifier_env env,\nkernel/bpf/verifier.c-873-\t\t\t\t\tstruct bpf_func_state state, int spi,\n--\nkernel/bpf/verifier.c=924=static bool is_dynptr_reg_valid_uninit(struct bpf_verifier_env env, struct bpf_reg_state reg)\n--\nkernel/bpf/verifier.c-942-\t STACK_DYNPTR slots, see mark_stack_slots_dynptr which calls\nkernel/bpf/verifier.c:943:\t * destroy_if_dynptr_stack_slot to ensure dynptr objects at the slots we are\nkernel/bpf/verifier.c-944-\t * touching are completely destructed before we reinitialize them for a new\nkernel/bpf/verifier.c:945:\t * one. For referenced ones, destroy_if_dynptr_stack_slot returns an error early\nkernel/bpf/verifier.c-946-\t * instead of delaying it until the end where the user will get \"Unreleased\n--\nkernel/bpf/verifier.c=3616=static int check_stack_write_fixed_off(struct bpf_verifier_env env,\n--\nkernel/bpf/verifier.c-3668-\nkernel/bpf/verifier.c:3669:\terr = destroy_if_dynptr_stack_slot(env, state, spi, false);\nkernel/bpf/verifier.c-3670-\tif (err)\n--\nkernel/bpf/verifier.c=3759=static int check_stack_write_var_off(struct bpf_verifier_env env,\n--\nkernel/bpf/verifier.c-3788-\t\tspi = bpf_get_spi(i);\nkernel/bpf/verifier.c:3789:\t\terr = destroy_if_dynptr_stack_slot(env, state, spi, false);\nkernel/bpf/verifier.c-3790-\t\tif (err)\n" }
27/3	2026/09/18 20:58	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 8548 output: 36 thoughts: 30 Thoughts: Here's my summary, as if I were thinking these thoughts: Analyzing `destroy_if_dynptr_stack_slot` in `kernel/bpf/verifier.c` Okay, time to dive into the implementation of `destroy_if_dynptr_stack_slot`. I need to understand exactly how this function handles dynamically allocated pointer (dynptr) stack slots, particularly within the BPF verifier. This is a critical function, potentially involved in memory safety, and ensuring we aren't introducing any exploitable vulnerabilities related to pointer manipulation is paramount. I'll need to pay close attention to the conditions under which the slot gets destroyed, any error handling, and how it interacts with other parts of the verifier's state. I need to understand what invariants this is supposed to maintain, and if it does so reliably. Understanding how it prevents memory leaks or double frees for dynptr data is key to my analysis. Let's see how they've structured the logic and what assumptions they've made. Let's dig in.
28/3	2026/09/18 20:58	tool	read-file	0m Args: { "File": "kernel/bpf/verifier.c", "FirstLine": 870, "LineCount": 55 } Results: { "Contents": " 870:\t}\n 871:\t\n 872:\tstatic int destroy_if_dynptr_stack_slot(struct bpf_verifier_env env,\n 873:\t\t\t\t\t\tstruct bpf_func_state state, int spi,\n 874:\t\t\t\t\t\tbool on_func_exit)\n 875:\t{\n 876:\t\tint err = 0;\n 877:\t\n 878:\t\t/* We always ensure that STACK_DYNPTR is never set partially,\n 879:\t\t * hence just checking for slot_type[0] is enough. This is\n 880:\t\t * different for STACK_SPILL, where it may be only set for\n 881:\t\t * 1 byte, so code has to use is_spilled_reg.\n 882:\t\t /\n 883:\t\tif (state-\u003estack[spi].slot_type[0] != STACK_DYNPTR)\n 884:\t\t\treturn 0;\n 885:\t\n 886:\t\t/ Reposition spi to first slot /\n 887:\t\tif (!state-\u003estack[spi].spilled_ptr.dynptr.first_slot)\n 888:\t\t\tspi = spi + 1;\n 889:\t\n 890:\t\t/\n 891:\t\t * A referenced dynptr can be overwritten only if there is at\n 892:\t\t * least one other dynptr sharing the same virtual ref parent,\n 893:\t\t * ensuring the reference can still be properly released.\n 894:\t\t /\n 895:\t\tif (dynptr_type_referenced(state-\u003estack[spi].spilled_ptr.dynptr.type) \u0026\u0026\n 896:\t\t dynptr_ref_cnt(env, state-\u003estack[spi].spilled_ptr.parent_id) \u003c= 1) {\n 897:\t\t\tif (on_func_exit) {\n 898:\t\t\t\tverbose(env, \"cannot return with referenced dynptr in callee stack\\n\");\n 899:\t\t\t\tbpf_diag_res(env, env-\u003einsn_idx,\n 900:\t\t\t\t\t \"referenced dynptr on function return\",\n 901:\t\t\t\t\t \"The departing stack frame contains the last dynptr that can release a referenced resource.\",\n 902:\t\t\t\t\t \"Release the referenced resource before returning from this function.\");\n 903:\t\t\t\treturn -EINVAL;\n 904:\t\t\t}\n 905:\t\n 906:\t\t\tverbose(env, \"cannot overwrite referenced dynptr\\n\");\n 907:\t\t\tbpf_diag_res(\n 908:\t\t\t\tenv, env-\u003einsn_idx, \"referenced dynptr overwrite\",\n 909:\t\t\t\t\"This stack slot contains a dynptr that owns or protects a referenced resource. Overwriting the last dynptr for that resource would lose the verifier-tracked release path.\",\n 910:\t\t\t\t\"Release or clone the dynptr so another live dynptr still tracks the referenced resource before overwriting this stack slot.\");\n 911:\t\t\treturn -EINVAL;\n 912:\t\t}\n 913:\t\n 914:\t\t/ Invalidate the dynptr and any derived slices /\n 915:\t\terr = release_reference(env, state-\u003estack[spi].spilled_ptr.id);\n 916:\t\tif (!err) {\n 917:\t\t\tmark_stack_slot_scratched(env, spi);\n 918:\t\t\tmark_stack_slot_scratched(env, spi - 1);\n 919:\t\t}\n 920:\t\n 921:\t\treturn err;\n 922:\t}\n 923:\t\n 924:\tstatic bool is_dynptr_reg_valid_uninit(struct bpf_verifier_env env, struct bpf_reg_state *reg)\n" }
29/3	2026/09/18 20:58	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 9800 output: 38 thoughts: 21 Thoughts: Here's my take on those thoughts, from my perspective as an expert: Investigating a Potential Issue in Function Exit Handling Okay, so we need to drill down on potential exit-related issues within this codebase. Given the nature of the problems we're probably seeing, I'm thinking we should specifically investigate the `prepare_func_exit` function. It seems like a logical place to look for potential problems when dealing with cleanup tasks. The line number, around 11043, feels like a likely spot in relation to the overall program flow. I'll focus my attention on how that function handles resources. I'll specifically look at resource release, and whether everything's being done in the correct order. I'll need to figure out what happens if something fails, and if there are any race conditions that might be present.
30/3	2026/09/18 20:58	tool	read-file	0m Args: { "File": "kernel/bpf/verifier.c", "FirstLine": 11065, "LineCount": 40 } Results: { "Contents": "11065:\t\t\t\t\t insn_idx, callee-\u003ecallsite);\n11066:\t\t\t\treturn -EFAULT;\n11067:\t\t\t}\n11068:\t\t} else {\n11069:\t\t\t/\n11070:\t\t\t * return to the caller whatever the callee had in the\n11071:\t\t\t * return register(s)\n11072:\t\t\t /\n11073:\t\t\tfor (i = 0; i \u003c nregs; i++) {\n11074:\t\t\t\tu32 regno = ret_regs[i];\n11075:\t\n11076:\t\t\t\tbpf_diag_mod_begin(env, \u0026caller-\u003eregs[regno], \u0026callee-\u003eregs[regno],\n11077:\t\t\t\t\t\t BPF_DIAG_MOD_WRITE);\n11078:\t\t\t\tcaller-\u003eregs[regno] = callee-\u003eregs[regno];\n11079:\t\t\t\tbpf_diag_mod_end(env);\n11080:\t\t\t}\n11081:\t\t}\n11082:\t\terr = destroy_dynptrs_on_func_exit(env, callee);\n11083:\t\tif (err)\n11084:\t\t\treturn err;\n11085:\t\n11086:\t\t/ for callbacks like bpf_loop or bpf_for_each_map_elem go back to callsite,\n11087:\t\t * there function call logic would reschedule callback visit. If iteration\n11088:\t\t * converges is_state_visited() would prune that visit eventually.\n11089:\t\t /\n11090:\t\tin_callback_fn = callee-\u003ein_callback_fn;\n11091:\t\tif (in_callback_fn)\n11092:\t\t\tinsn_idx = callee-\u003ecallsite;\n11093:\t\telse\n11094:\t\t\tinsn_idx = callee-\u003ecallsite + 1;\n11095:\t\n11096:\t\tif (env-\u003elog.level \u0026 BPF_LOG_LEVEL) {\n11097:\t\t\tverbose(env, \"returning from callee:\\n\");\n11098:\t\t\tprint_verifier_state(env, state, callee-\u003eframeno, true);\n11099:\t\t\tverbose(env, \"to caller at %d:\\n\", insn_idx);\n11100:\t\t\tprint_verifier_state(env, state, caller-\u003eframeno, true);\n11101:\t\t}\n11102:\t\taccount_processed_insns(env, callee, caller);\n11103:\t\t/* clear everything in the callee. In case of exceptional exits using\n11104:\t\t * bpf_throw, this will be done by copy_verifier_state for extra frames. */\n" }
31/3	2026/09/18 20:58	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 10768 output: 31 thoughts: 1209 Thoughts: Analyzing Dynptr Stack Cleanup for BPF Subprograms Okay, let's break down this BPF patch and its implications. My primary concern here is understanding the dynamic pointer (`dynptr`) lifecycle within BPF subprograms, especially regarding stack management and potential memory safety issues. The core problem seems to be the behavior of `dynptr`s when a subprogram exits and how slices derived from those `dynptr`s are handled. Specifically, I'm focusing on scenarios where a subprogram creates a `dynptr` on its stack, uses it to obtain a slice, returns that slice, and then the stack frame is cleaned up. The crucial question is: does the slice become invalid, and if so, how is that enforced? The test case `invalid_dynptr_returned_slice` is illuminating here. It demonstrates the issue of returning a slice pointing to memory managed by a now-invalidated `dynptr`. Before this patch, it seems like the slice wouldn't be invalidated, leading to possible use-after-free or reference leak issues. The patch's key function, `destroy_dynptrs_on_func_exit`, is what I need to understand. This is verifier internal bookkeeping. It iterates over the callee's stack, looking for `STACK_DYNPTR` entries, and then calls `destroy_if_dynptr_stack_slot`. The `destroy_if_dynptr_stack_slot` function is where the magic happens: it checks if the `dynptr` is referenced and, if so, invalidates it and any derived slices by calling `release_reference`. It's a critical mechanism to ensure that slices aren't left dangling after the `dynptr` is destroyed. If the `dynptr` had a reference, the verifier will return an error as well. Now, for a sanitizer perspective, I have to consider: what bugs are we fixing, and what might we introduce? 1. Verifier-side analysis: This patch operates within the verifier, so it should not introduce user-space issues. The verifier checks at BPF program load (bpf syscall), and `destroy_dynptrs_on_func_exit` deals with internal bookkeeping for the `bpf_func_state`. Critically, no kernel structures are exposed to user space (except verifier log strings), there are no allocations, and there isn't uninitialized memory read/copied. This reduces KMSAN risks significantly. The `destroy_dynptrs_on_func_exit` function iterates over the `callee->allocated_stack / BPF_REG_SIZE`, so I want to make sure the stack allocation and indexing is well-defined. 2. Runtime implications: Fixing this bug prevents a BPF program from accessing freed memory, or causing a reference leak. If the bug were present, a BPF program could retrieve a stack `dynptr` slice in a subprogram, then access that slice after the `dynptr` was destroyed. This leads to use-after-free, particularly KASAN issues with ringbuf or skb memory. 3. KMSAN risks: Let's walk through the KMSAN criteria carefully. This patch doesn't: * Send kernel structures to user space. * Introduce conditional logic dependent on uninitialized variables. * Allocate complex data structures with uninitialized fields. * Modify bounds checks in a way that risks reading uninitialized memory. Because of this careful review of the code, this patch does not introduce KMSAN-specific risks. The stack structures are fully initialized before use. The patch primarily addresses use-after-free (KASAN), and reference leak bugs, which are not KMSAN problems.
32/3	2026/09/18 20:58	tool	grepper	0m Args: { "Expression": "allocated_stack", "PathPrefix": "kernel/bpf/verifier.c" } Results: { "Output": "kernel/bpf/verifier.c=588=static bool is_spi_bounds_valid(struct bpf_func_state state, int spi, int nr_slots)\nkernel/bpf/verifier.c-589-{\nkernel/bpf/verifier.c:590: int allocated_slots = state-\u003eallocated_stack / BPF_REG_SIZE;\nkernel/bpf/verifier.c-591-\nkernel/bpf/verifier.c-592- / We need to check that slots between [spi - nr_slots + 1, spi] are\nkernel/bpf/verifier.c:593:\t* within [0, allocated_stack).\nkernel/bpf/verifier.c-594-\t\n--\nkernel/bpf/verifier.c=847=static int destroy_dynptrs_on_func_exit(struct bpf_verifier_env env,\n--\nkernel/bpf/verifier.c-851-\nkernel/bpf/verifier.c:852:\tfor (i = 0; i \u003c callee-\u003eallocated_stack / BPF_REG_SIZE; i++) {\nkernel/bpf/verifier.c-853-\t\tstruct bpf_stack_state slot = \u0026callee-\u003estack[i];\n--\nkernel/bpf/verifier.c=1427=static int copy_stack_state(struct bpf_func_state dst, const struct bpf_func_state src)\nkernel/bpf/verifier.c-1428-{\nkernel/bpf/verifier.c:1429:\tsize_t n = src-\u003eallocated_stack / BPF_REG_SIZE;\nkernel/bpf/verifier.c-1430-\n--\nkernel/bpf/verifier.c-1435-\nkernel/bpf/verifier.c:1436:\tdst-\u003eallocated_stack = src-\u003eallocated_stack;\nkernel/bpf/verifier.c-1437-\n--\nkernel/bpf/verifier.c=1452=static int resize_reference_state(struct bpf_verifier_state state, size_t n)\n--\nkernel/bpf/verifier.c-1462-\nkernel/bpf/verifier.c:1463:/* Possibly update state-\u003eallocated_stack to be at least size bytes. Also\nkernel/bpf/verifier.c-1464- * possibly update the function's high-water mark in its bpf_subprog_info.\n--\nkernel/bpf/verifier.c=1466=static int grow_stack_state(struct bpf_verifier_env env, struct bpf_func_state state, int size)\nkernel/bpf/verifier.c-1467-{\nkernel/bpf/verifier.c:1468:\tsize_t old_n = state-\u003eallocated_stack / BPF_REG_SIZE, n;\nkernel/bpf/verifier.c-1469-\n--\nkernel/bpf/verifier.c-1480-\nkernel/bpf/verifier.c:1481:\tstate-\u003eallocated_stack = size;\nkernel/bpf/verifier.c-1482-\n--\nkernel/bpf/verifier.c=6266=static int check_ptr_to_map_access(struct bpf_verifier_env env,\n--\nkernel/bpf/verifier.c-6334- The minimum valid offset is -MAX_BPF_STACK for writes, and\nkernel/bpf/verifier.c:6335: * -state-\u003eallocated_stack for reads.\nkernel/bpf/verifier.c-6336- /\nkernel/bpf/verifier.c=6337=static int check_stack_slot_within_bounds(struct bpf_verifier_env env,\n--\nkernel/bpf/verifier.c-6346-\telse\nkernel/bpf/verifier.c:6347:\t\tmin_valid_off = -state-\u003eallocated_stack;\nkernel/bpf/verifier.c-6348-\n--\nkernel/bpf/verifier.c=7001=static int check_stack_range_initialized(\n--\nkernel/bpf/verifier.c-7070-\t\tspi = slot / BPF_REG_SIZE;\nkernel/bpf/verifier.c:7071:\t\tif (state-\u003eallocated_stack \u003c= slot) {\nkernel/bpf/verifier.c:7072:\t\t\tverbose(env, \"allocated_stack too small\\n\");\nkernel/bpf/verifier.c-7073-\t\t\treturn -EFAULT;\n--\nkernel/bpf/verifier.c=8012=static int widen_imprecise_scalars(struct bpf_verifier_env env,\n--\nkernel/bpf/verifier.c-8027-\nkernel/bpf/verifier.c:8028:\t\tnum_slots = min(fold-\u003eallocated_stack / BPF_REG_SIZE,\nkernel/bpf/verifier.c:8029:\t\t\t\tfcur-\u003eallocated_stack / BPF_REG_SIZE);\nkernel/bpf/verifier.c-8030-\t\tfor (i = 0; i \u003c num_slots; i++) {\n--\nkernel/bpf/verifier.c=17189=static void collect_linked_regs(struct bpf_verifier_env env,\n--\nkernel/bpf/verifier.c-17209-\t\t}\nkernel/bpf/verifier.c:17210:\t\tfor (j = 0; j \u003c func-\u003eallocated_stack / BPF_REG_SIZE; j++) {\nkernel/bpf/verifier.c-17211-\t\t\tif (!bpf_is_spilled_reg(\u0026func-\u003estack[j]))\n" }
33/3	2026/09/18 20:58	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 14233 output: 241 thoughts: 850 Thoughts: KMSAN Assessment: No Need for Dedicated Fuzzing Okay, let's break this down. My analysis focuses on whether this patch necessitates a KMSAN (Kernel Memory Sanitizer) fuzzing session. The code, specifically `grow_stack_state` and `destroy_dynptrs_on_func_exit`, deals with stack allocation and deallocation within BPF subprograms, particularly concerning "dynptrs" and their slices. The core of the patch is about ensuring these dynptrs and their associated memory are properly cleaned up upon subprogram exit. This prevents dangling pointers and potential memory safety issues, namely use-after-free or out-of-bounds access. I see that `grow_stack_state` is careful to reallocate and zero the stack, and that `callee->stack[i]` is fully initialized. The `destroy_dynptrs_on_func_exit` function iterates through allocated stack slots, and destroys dynamic pointers. There's no introduction of uninitialized memory here – local variables are initialized before use, and there's no data being leaked to userspace. The critical point is that the memory safety concerns this patch addresses—use-after-free, memory corruption, and reference leaks from dangling pointers—are already detectable by KASAN (Kernel Address Sanitizer), refcount, and leak detectors. KMSAN, on the other hand, detects reads of uninitialized memory and leaks of uninitialized kernel memory to userspace. Since this patch doesn't introduce uninitialized memory or expose a means of leaking it, KMSAN isn't the right tool for the job. The patch's goal is to improve the BPF verifier's tracking of dynptrs to prevent misuse of dynamically allocated memory. It strengthens the existing verifier and adds safety against the memory issues cited above. A failure to clean up memory correctly would lead to memory errors detected by existing mechanisms, not uninitialized memory issues that only KMSAN would find. This patch doesn't create uninitialized memory hazards. Therefore, applying the rule set within the patch, my determination is that `NeedsKMSAN = false`. KASAN, in conjunction with other standard bug detectors, is perfectly adequate for assessing the safety of this patch, and dedicated KMSAN fuzzing would be an unnecessary expenditure of resources.
34/3	2026/09/18 20:59	tool	set-results	0m Args: { "KMSANReasoning": "The patch modifies the BPF verifier (kernel/bpf/verifier.c) to tear down local dynptrs and invalidate derived slices when returning from a BPF subprogram (prepare_func_exit). It also adds a check ensuring that departing stack frames cannot drop the last dynptr referencing a resource.\n\nFrom a memory safety perspective:\n1. The bug being addressed relates to stale slices and reference tracking across stack frames, which at runtime in BPF programs could lead to use-after-free or dangling pointer dereferences. These memory corruption bugs are caught by standard KASAN, not KMSAN.\n2. The patch touches only static verifier verification state logic and selftests. No kernel-to-userspace copies (info-leaks), uninitialized stack/heap allocations, or branches on uninitialized memory are introduced or exposed. All variables in the new verifier functions are fully initialized.\n\nTherefore, this change does not introduce or expose uninitialized memory risks, and a dedicated KMSAN fuzzing session is not warranted.", "NeedsKMSAN": false } Results: { "KMSANReasoning": "The patch modifies the BPF verifier (kernel/bpf/verifier.c) to tear down local dynptrs and invalidate derived slices when returning from a BPF subprogram (prepare_func_exit). It also adds a check ensuring that departing stack frames cannot drop the last dynptr referencing a resource.\n\nFrom a memory safety perspective:\n1. The bug being addressed relates to stale slices and reference tracking across stack frames, which at runtime in BPF programs could lead to use-after-free or dangling pointer dereferences. These memory corruption bugs are caught by standard KASAN, not KMSAN.\n2. The patch touches only static verifier verification state logic and selftests. No kernel-to-userspace copies (info-leaks), uninitialized stack/heap allocations, or branches on uninitialized memory are introduced or exposed. All variables in the new verifier functions are fully initialized.\n\nTherefore, this change does not introduce or expose uninitialized memory risks, and a dedicated KMSAN fuzzing session is not warranted.", "NeedsKMSAN": false }

LLM Calls Summary:
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Tool Calls Summary:
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