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BUG: KCSAN: data-race in p9_conn_cancel / p9_poll_workfn

write to 0xffff888164f81828 of 4 bytes by task 4264 on cpu 1:
 p9_conn_cancel+0x89/0x400 net/9p/trans_fd.c:199
 p9_write_work+0x3ac/0x750 net/9p/trans_fd.c:522
 process_one_work kernel/workqueue.c:3236 [inline]
 process_scheduled_works+0x483/0x9a0 kernel/workqueue.c:3317
 worker_thread+0x51d/0x6f0 kernel/workqueue.c:3398
 kthread+0x4ae/0x520 kernel/kthread.c:464
 ret_from_fork+0x4b/0x60 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

read to 0xffff888164f81828 of 4 bytes by task 9 on cpu 0:
 p9_poll_mux net/9p/trans_fd.c:625 [inline]
 p9_poll_workfn+0xc0/0x410 net/9p/trans_fd.c:1177
 process_one_work kernel/workqueue.c:3236 [inline]
 process_scheduled_works+0x483/0x9a0 kernel/workqueue.c:3317
 worker_thread+0x51d/0x6f0 kernel/workqueue.c:3398
 kthread+0x4ae/0x520 kernel/kthread.c:464
 ret_from_fork+0x4b/0x60 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

value changed: 0x00000000 -> 0xffffffe0

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 9 Comm: kworker/0:1 Not tainted 6.14.0-rc1-syzkaller-00081-gbb066fe812d6 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 12/27/2024
Workqueue: events p9_poll_workfn
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