==================================================================
BUG: KCSAN: data-race in bq_flush_to_queue / cpu_map_kthread_run

write to 0xffff88811ce9c400 of 8 bytes by task 3733 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 0xffff88811ce9c400 of 8 bytes by task 3732 on cpu 1:
 __ptr_ring_produce include/linux/ptr_ring.h:106 [inline]
 bq_flush_to_queue+0x124/0x350 kernel/bpf/cpumap.c:730
 __cpu_map_flush+0x38/0x80 kernel/bpf/cpumap.c:808
 xdp_do_flush+0xf9/0x160 net/core/filter.c:4348
 xdp_test_run_batch net/bpf/test_run.c:348 [inline]
 bpf_test_run_xdp_live+0xd67/0x11d0 net/bpf/test_run.c:379
 bpf_prog_test_run_xdp+0x525/0x970 net/bpf/test_run.c:1388
 bpf_prog_test_run+0x22a/0x390 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+0xd8/0x2a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0xffff88811cc33070 -> 0x0000000000000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 3732 Comm: syz.2.94 Not tainted syzkaller #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
==================================================================