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BUG: KCSAN: data-race in __bpf_get_stackid / bcmp

write to 0xffff88811b382190 of 96 bytes by task 3851 on cpu 0:
 __bpf_get_stackid+0x737/0x7d0 kernel/bpf/stackmap.c:311
 ____bpf_get_stackid kernel/bpf/stackmap.c:344 [inline]
 bpf_get_stackid+0xf3/0x130 kernel/bpf/stackmap.c:323
 ____bpf_get_stackid_raw_tp kernel/trace/bpf_trace.c:1628 [inline]
 bpf_get_stackid_raw_tp+0xf6/0x120 kernel/trace/bpf_trace.c:1617
 bpf_prog_53f0063d4d7f65ce+0x2a/0x32
 bpf_dispatcher_nop_func include/linux/bpf.h:1378 [inline]
 __bpf_prog_run include/linux/filter.h:723 [inline]
 bpf_prog_run include/linux/filter.h:730 [inline]
 __bpf_trace_run kernel/trace/bpf_trace.c:2075 [inline]
 bpf_trace_run2+0x107/0x1d0 kernel/trace/bpf_trace.c:2116
 __traceiter_kfree+0x2e/0x50 include/trace/events/kmem.h:97
 __do_trace_kfree include/trace/events/kmem.h:97 [inline]
 trace_kfree include/trace/events/kmem.h:97 [inline]
 kfree+0x353/0x3c0 mm/slub.c:6865
 vfree+0x28d/0x3a0 mm/vmalloc.c:3471
 bpf_check+0x9ceb/0xc860 kernel/bpf/verifier.c:25389
 bpf_prog_load+0xf6e/0x1140 kernel/bpf/syscall.c:3088
 __sys_bpf+0x469/0x7c0 kernel/bpf/syscall.c:6164
 __do_sys_bpf kernel/bpf/syscall.c:6274 [inline]
 __se_sys_bpf kernel/bpf/syscall.c:6272 [inline]
 __x64_sys_bpf+0x41/0x50 kernel/bpf/syscall.c:6272
 x64_sys_call+0x28e1/0x3000 arch/x86/include/generated/asm/syscalls_64.h:322
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xca/0x2b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88811b3821d0 of 8 bytes by task 3819 on cpu 1:
 memcmp lib/string.c:683 [inline]
 bcmp+0x23/0x90 lib/string.c:715
 memcmp include/linux/fortify-string.h:727 [inline]
 __bpf_get_stackid+0x382/0x7d0 kernel/bpf/stackmap.c:302
 ____bpf_get_stackid kernel/bpf/stackmap.c:344 [inline]
 bpf_get_stackid+0xf3/0x130 kernel/bpf/stackmap.c:323
 ____bpf_get_stackid_raw_tp kernel/trace/bpf_trace.c:1628 [inline]
 bpf_get_stackid_raw_tp+0xf6/0x120 kernel/trace/bpf_trace.c:1617
 bpf_prog_53f0063d4d7f65ce+0x2a/0x32
 bpf_dispatcher_nop_func include/linux/bpf.h:1378 [inline]
 __bpf_prog_run include/linux/filter.h:723 [inline]
 bpf_prog_run include/linux/filter.h:730 [inline]
 __bpf_trace_run kernel/trace/bpf_trace.c:2075 [inline]
 bpf_trace_run2+0x107/0x1d0 kernel/trace/bpf_trace.c:2116
 __traceiter_kfree+0x2e/0x50 include/trace/events/kmem.h:97
 __do_trace_kfree include/trace/events/kmem.h:97 [inline]
 trace_kfree include/trace/events/kmem.h:97 [inline]
 kfree+0x353/0x3c0 mm/slub.c:6865
 selinux_release_secctx+0x45/0x80 security/selinux/hooks.c:6849
 security_release_secctx+0x42/0x60 security/security.c:3890
 audit_log_subj_ctx+0xe1/0x3e0 kernel/audit.c:2301
 audit_log_task_context+0x48/0x70 kernel/audit.c:2344
 audit_log_task+0xf4/0x250 kernel/auditsc.c:2924
 audit_seccomp+0x61/0x100 kernel/auditsc.c:2974
 seccomp_log kernel/seccomp.c:1048 [inline]
 __seccomp_filter+0x843/0x1260 kernel/seccomp.c:1344
 __secure_computing+0x82/0x150 kernel/seccomp.c:1404
 syscall_trace_enter+0xcf/0x1e0 kernel/entry/syscall-common.c:44
 syscall_enter_from_user_mode_work include/linux/entry-common.h:78 [inline]
 syscall_enter_from_user_mode include/linux/entry-common.h:109 [inline]
 do_syscall_64+0xa4/0x2b0 arch/x86/entry/syscall_64.c:90
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0xffffffff81575954 -> 0xffffffff81626731

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 3819 Comm: syz.0.124 Not tainted syzkaller #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
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