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BUG: KCSAN: data-race in __bpf_get_stackid / bcmp

write to 0xffff8881198e9f78 of 104 bytes by task 21074 on cpu 1:
 __bpf_get_stackid+0x761/0x800 kernel/bpf/stackmap.c:288
 ____bpf_get_stackid kernel/bpf/stackmap.c:324 [inline]
 bpf_get_stackid+0xee/0x120 kernel/bpf/stackmap.c:300
 ____bpf_get_stackid_raw_tp kernel/trace/bpf_trace.c:1810 [inline]
 bpf_get_stackid_raw_tp+0xf6/0x120 kernel/trace/bpf_trace.c:1799
 bpf_prog_e6fc920cfeff8120+0x2a/0x32
 bpf_dispatcher_nop_func include/linux/bpf.h:1332 [inline]
 __bpf_prog_run include/linux/filter.h:718 [inline]
 bpf_prog_run include/linux/filter.h:725 [inline]
 __bpf_trace_run kernel/trace/bpf_trace.c:2257 [inline]
 bpf_trace_run2+0x107/0x1c0 kernel/trace/bpf_trace.c:2298
 __traceiter_kfree+0x2e/0x50 include/trace/events/kmem.h:94
 __do_trace_kfree include/trace/events/kmem.h:94 [inline]
 trace_kfree include/trace/events/kmem.h:94 [inline]
 kfree+0x27b/0x320 mm/slub.c:4866
 check_cfg+0xe7f/0x1110 kernel/bpf/verifier.c:17915
 bpf_check+0x1333/0xd9e0 kernel/bpf/verifier.c:24683
 bpf_prog_load+0xedd/0x1070 kernel/bpf/syscall.c:2979
 __sys_bpf+0x462/0x7b0 kernel/bpf/syscall.c:6029
 __do_sys_bpf kernel/bpf/syscall.c:6139 [inline]
 __se_sys_bpf kernel/bpf/syscall.c:6137 [inline]
 __x64_sys_bpf+0x41/0x50 kernel/bpf/syscall.c:6137
 x64_sys_call+0x2aea/0x2ff0 arch/x86/include/generated/asm/syscalls_64.h:322
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd2/0x200 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff8881198e9fa8 of 8 bytes by task 21037 on cpu 0:
 memcmp lib/string.c:683 [inline]
 bcmp+0x23/0x90 lib/string.c:715
 memcmp include/linux/fortify-string.h:727 [inline]
 __bpf_get_stackid+0x371/0x800 kernel/bpf/stackmap.c:279
 ____bpf_get_stackid kernel/bpf/stackmap.c:324 [inline]
 bpf_get_stackid+0xee/0x120 kernel/bpf/stackmap.c:300
 ____bpf_get_stackid_raw_tp kernel/trace/bpf_trace.c:1810 [inline]
 bpf_get_stackid_raw_tp+0xf6/0x120 kernel/trace/bpf_trace.c:1799
 bpf_prog_e6fc920cfeff8120+0x2a/0x32
 bpf_dispatcher_nop_func include/linux/bpf.h:1332 [inline]
 __bpf_prog_run include/linux/filter.h:718 [inline]
 bpf_prog_run include/linux/filter.h:725 [inline]
 __bpf_trace_run kernel/trace/bpf_trace.c:2257 [inline]
 bpf_trace_run2+0x107/0x1c0 kernel/trace/bpf_trace.c:2298
 __traceiter_kfree+0x2e/0x50 include/trace/events/kmem.h:94
 __do_trace_kfree include/trace/events/kmem.h:94 [inline]
 trace_kfree include/trace/events/kmem.h:94 [inline]
 kfree+0x27b/0x320 mm/slub.c:4866
 audit_log_d_path+0xf4/0x150 kernel/audit.c:2160
 audit_log_d_path_exe+0x42/0x70 kernel/audit.c:2219
 audit_log_task+0x1e9/0x250 kernel/auditsc.c:2957
 audit_seccomp+0x61/0x100 kernel/auditsc.c:3004
 seccomp_log kernel/seccomp.c:1033 [inline]
 __seccomp_filter+0x69d/0x10d0 kernel/seccomp.c:1328
 __secure_computing+0x82/0x150 kernel/seccomp.c:1388
 syscall_trace_enter+0xcf/0x1e0 kernel/entry/syscall-common.c:44
 syscall_enter_from_user_mode_work include/linux/entry-common.h:95 [inline]
 syscall_enter_from_user_mode include/linux/entry-common.h:125 [inline]
 do_syscall_64+0xac/0x200 arch/x86/entry/syscall_64.c:90
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0xffffffff815623d2 -> 0xffffffff81639663

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 21037 Comm: syz.4.6104 Tainted: G        W           syzkaller #0 PREEMPT(voluntary) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
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