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BUG: KCSAN: data-race in __bpf_get_stackid / bcmp

write to 0xffff88813deba190 of 104 bytes by task 3917 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:6858
 vfree+0x28d/0x3a0 mm/vmalloc.c:3471
 bpf_prog_calc_tag+0x1c2/0x1e0 kernel/bpf/core.c:331
 resolve_pseudo_ldimm64+0x45/0x740 kernel/bpf/verifier.c:21047
 bpf_check+0xf8c/0xc860 kernel/bpf/verifier.c:25217
 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+0xd8/0x2a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88813deba1c8 of 8 bytes by task 3866 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:6858
 create_io_worker+0x2d9/0x360 io_uring/io-wq.c:915
 io_wq_create_worker io_uring/io-wq.c:339 [inline]
 io_wq_enqueue+0x2c1/0x3a0 io_uring/io-wq.c:1038
 io_queue_iowq+0x208/0x2f0 io_uring/io_uring.c:491
 io_req_task_submit+0x69/0xa0 io_uring/io_uring.c:1432
 io_handle_tw_list+0x1f7/0x230 io_uring/io_uring.c:1121
 tctx_task_work_run+0x42/0x160 io_uring/io_uring.c:1181
 tctx_task_work+0x3f/0x80 io_uring/io_uring.c:1199
 task_work_run+0x131/0x1a0 kernel/task_work.c:233
 io_run_task_work+0x1e8/0x280 io_uring/io_uring.h:490
 io_cqring_wait io_uring/io_uring.c:2644 [inline]
 __do_sys_io_uring_enter io_uring/io_uring.c:3316 [inline]
 __se_sys_io_uring_enter+0xad3/0x1a30 io_uring/io_uring.c:3216
 __x64_sys_io_uring_enter+0x78/0x90 io_uring/io_uring.c:3216
 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+0xd8/0x2a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0xffffffff81e82fc7 -> 0xffffffff8162e73e

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 3866 Comm: syz.0.120 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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