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BUG: KCSAN: data-race in p9_conn_cancel / p9_write_work

write to 0xffff8881443bd828 of 4 bytes by task 19633 on cpu 0:
 p9_conn_cancel+0x89/0x400 net/9p/trans_fd.c:199
 p9_poll_mux net/9p/trans_fd.c:631 [inline]
 p9_poll_workfn+0x133/0x420 net/9p/trans_fd.c:1177
 process_one_work kernel/workqueue.c:3231 [inline]
 process_scheduled_works+0x483/0x9a0 kernel/workqueue.c:3312
 worker_thread+0x526/0x730 kernel/workqueue.c:3393
 kthread+0x1d1/0x210 kernel/kthread.c:389
 ret_from_fork+0x4b/0x60 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

read to 0xffff8881443bd828 of 4 bytes by task 19705 on cpu 1:
 p9_write_work+0x26/0x750 net/9p/trans_fd.c:453
 process_one_work kernel/workqueue.c:3231 [inline]
 process_scheduled_works+0x483/0x9a0 kernel/workqueue.c:3312
 worker_thread+0x526/0x730 kernel/workqueue.c:3393
 kthread+0x1d1/0x210 kernel/kthread.c:389
 ret_from_fork+0x4b/0x60 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

value changed: 0x00000000 -> 0xffffff98

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 19705 Comm: kworker/1:18 Tainted: G        W          6.9.0-syzkaller-08284-gea5f6ad9ad96 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/02/2024
Workqueue: events p9_write_work
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