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BUG: KCSAN: data-race in __bpf_get_stackid / bcmp

write to 0xffff8881713e2190 of 96 bytes by task 26510 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+0xe9/0x120 kernel/bpf/stackmap.c:300
 ____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:1350 [inline]
 __bpf_prog_run include/linux/filter.h:721 [inline]
 bpf_prog_run include/linux/filter.h:728 [inline]
 __bpf_trace_run kernel/trace/bpf_trace.c:2075 [inline]
 bpf_trace_run2+0x107/0x1c0 kernel/trace/bpf_trace.c:2116
 __do_trace_kfree include/trace/events/kmem.h:97 [inline]
 trace_kfree include/trace/events/kmem.h:97 [inline]
 kfree+0x351/0x400 mm/slub.c:6813
 security_inode_init_security+0x2da/0x330 security/security.c:1895
 shmem_symlink+0xc9/0x3d0 mm/shmem.c:4099
 vfs_symlink+0xd4/0x1e0 fs/namei.c:4817
 do_symlinkat+0xc7/0x3c0 fs/namei.c:4843
 __do_sys_symlinkat fs/namei.c:4859 [inline]
 __se_sys_symlinkat fs/namei.c:4856 [inline]
 __x64_sys_symlinkat+0x5a/0x70 fs/namei.c:4856
 x64_sys_call+0x2941/0x3000 arch/x86/include/generated/asm/syscalls_64.h:267
 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 0xffff8881713e21b0 of 8 bytes by task 26498 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+0xe9/0x120 kernel/bpf/stackmap.c:300
 ____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:1350 [inline]
 __bpf_prog_run include/linux/filter.h:721 [inline]
 bpf_prog_run include/linux/filter.h:728 [inline]
 __bpf_trace_run kernel/trace/bpf_trace.c:2075 [inline]
 bpf_trace_run2+0x107/0x1c0 kernel/trace/bpf_trace.c:2116
 __do_trace_kfree include/trace/events/kmem.h:97 [inline]
 trace_kfree include/trace/events/kmem.h:97 [inline]
 kfree+0x351/0x400 mm/slub.c:6813
 ___sys_recvmsg+0x135/0x370 net/socket.c:2893
 do_recvmmsg+0x1ef/0x540 net/socket.c:2987
 __sys_recvmmsg net/socket.c:3061 [inline]
 __do_sys_recvmmsg net/socket.c:3084 [inline]
 __se_sys_recvmmsg net/socket.c:3077 [inline]
 __x64_sys_recvmmsg+0xe5/0x170 net/socket.c:3077
 x64_sys_call+0x27aa/0x3000 arch/x86/include/generated/asm/syscalls_64.h:300
 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

value changed: 0xffffffff844e2005 -> 0xffffffff81d1edfa

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 26498 Comm: syz.7.18178 Tainted: G        W           syzkaller #0 PREEMPT(voluntary) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
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