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BUG: KCSAN: data-race in bq_flush_to_queue / cpu_map_kthread_run

write to 0xffff88810429b108 of 8 bytes by task 22368 on cpu 0:
 __ptr_ring_zero_tail include/linux/ptr_ring.h:259 [inline]
 __ptr_ring_discard_one include/linux/ptr_ring.h:291 [inline]
 __ptr_ring_consume include/linux/ptr_ring.h:311 [inline]
 __ptr_ring_consume_batched include/linux/ptr_ring.h:323 [inline]
 cpu_map_kthread_run+0x529/0x1560 kernel/bpf/cpumap.c:332
 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 0xffff88810429b108 of 8 bytes by task 22367 on cpu 1:
 __ptr_ring_produce include/linux/ptr_ring.h:106 [inline]
 bq_flush_to_queue+0x124/0x350 kernel/bpf/cpumap.c:730
 bq_enqueue kernel/bpf/cpumap.c:754 [inline]
 cpu_map_enqueue+0x1a6/0x1c0 kernel/bpf/cpumap.c:780
 __xdp_do_redirect_frame net/core/filter.c:4472 [inline]
 xdp_do_redirect_frame+0x27c/0x560 net/core/filter.c:4523
 xdp_test_run_batch net/bpf/test_run.c:330 [inline]
 bpf_test_run_xdp_live+0x98c/0x11d0 net/bpf/test_run.c:379
 bpf_prog_test_run_xdp+0x525/0x970 net/bpf/test_run.c:1388
 bpf_prog_test_run+0x204/0x340 kernel/bpf/syscall.c:4703
 __sys_bpf+0x4c0/0x7c0 kernel/bpf/syscall.c:6182
 __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+0xca/0x2b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0xffff8881843f8070 -> 0x0000000000000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 22367 Comm: syz.6.7655 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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