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BUG: KCSAN: data-race in __bpf_get_stackid / bcmp

write to 0xffff8881204eae20 of 144 bytes by task 3312 on cpu 0:
 __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+0x104/0x1c0 kernel/trace/bpf_trace.c:2298
 __traceiter_kfree+0x2b/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:4881
 ref_tracker_free+0x28d/0x3e0 lib/ref_tracker.c:340
 __netns_tracker_free include/net/net_namespace.h:374 [inline]
 put_net_track include/net/net_namespace.h:389 [inline]
 __sk_destruct+0x2f1/0x4c0 net/core/sock.c:2368
 sk_destruct net/core/sock.c:2401 [inline]
 __sk_free+0x227/0x270 net/core/sock.c:2412
 sk_free+0x39/0x80 net/core/sock.c:2423
 sock_put include/net/sock.h:1962 [inline]
 tcp_close+0x8d/0xd0 net/ipv4/tcp.c:3278
 inet_release+0xcb/0xf0 net/ipv4/af_inet.c:435
 __sock_release net/socket.c:649 [inline]
 sock_close+0x6b/0x150 net/socket.c:1439
 __fput+0x298/0x650 fs/file_table.c:468
 fput_close_sync+0x6e/0x120 fs/file_table.c:573
 __do_sys_close fs/open.c:1587 [inline]
 __se_sys_close fs/open.c:1572 [inline]
 __x64_sys_close+0x56/0xf0 fs/open.c:1572
 x64_sys_call+0x2738/0x2ff0 arch/x86/include/generated/asm/syscalls_64.h:4
 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 0xffff8881204eae78 of 8 bytes by task 9301 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+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+0x104/0x1c0 kernel/trace/bpf_trace.c:2298
 __traceiter_kfree+0x2b/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:4881
 krealloc_noprof+0x136/0x2d0 mm/slub.c:-1
 copy_array+0x63/0xf0 kernel/bpf/verifier.c:1388
 copy_verifier_state+0x67/0x560 kernel/bpf/verifier.c:1738
 is_state_visited kernel/bpf/verifier.c:19630 [inline]
 do_check+0x2819/0x7a10 kernel/bpf/verifier.c:20030
 do_check_common+0xc3a/0x12a0 kernel/bpf/verifier.c:23264
 do_check_main kernel/bpf/verifier.c:23347 [inline]
 bpf_check+0x942b/0xd9e0 kernel/bpf/verifier.c:24707
 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

value changed: 0xffffffff81628b8d -> 0xffffffff844af09b

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 9301 Comm: syz.0.2562 Tainted: G        W           syzkaller #0 PREEMPT(voluntary) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
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