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BUG: KCSAN: data-race in __bpf_get_stackid / bcmp

write to 0xffff88810a110440 of 96 bytes by task 3396 on cpu 1:
 __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:1376 [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
 __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:6863
 vfree+0x28d/0x3a0 mm/vmalloc.c:3471
 __bpf_prog_free+0x86/0xa0 kernel/bpf/core.c:294
 bpf_prog_unlock_free include/linux/filter.h:1129 [inline]
 bpf_jit_free+0x273/0x2f0 arch/x86/net/bpf_jit_comp.c:3954
 bpf_prog_free_deferred+0x41d/0x470 kernel/bpf/core.c:2919
 process_one_work kernel/workqueue.c:3257 [inline]
 process_scheduled_works+0x4ce/0x9d0 kernel/workqueue.c:3340
 worker_thread+0x582/0x770 kernel/workqueue.c:3421
 kthread+0x489/0x510 kernel/kthread.c:463
 ret_from_fork+0x149/0x290 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246

read to 0xffff88810a110480 of 8 bytes by task 7748 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+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:1376 [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
 __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:6863
 __sock_kfree_s net/core/sock.c:2917 [inline]
 sock_kfree_s+0x28/0x50 net/core/sock.c:2923
 ____sys_sendmsg+0x404/0x4a0 net/socket.c:2606
 __sys_sendmsg_sock+0x28/0x40 net/socket.c:2658
 io_sendmsg+0x163/0x490 io_uring/net.c:562
 __io_issue_sqe+0xfe/0x2e0 io_uring/io_uring.c:1792
 io_issue_sqe+0x56/0xa80 io_uring/io_uring.c:1815
 io_queue_sqe io_uring/io_uring.c:2042 [inline]
 io_submit_sqe io_uring/io_uring.c:2320 [inline]
 io_submit_sqes+0x78b/0x11b0 io_uring/io_uring.c:2434
 __do_sys_io_uring_enter io_uring/io_uring.c:3280 [inline]
 __se_sys_io_uring_enter+0x1bd/0x1a30 io_uring/io_uring.c:3219
 __x64_sys_io_uring_enter+0x78/0x90 io_uring/io_uring.c:3219
 x64_sys_call+0x27e4/0x3000 arch/x86/include/generated/asm/syscalls_64.h:427
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd8/0x2c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0xffffffff81e86256 -> 0xffffffff813d63f2

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 7748 Comm: syz.3.1223 Tainted: G        W           syzkaller #0 PREEMPT(voluntary) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
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