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SubjectKCSAN: data-race in poll_schedule_timeout.constprop.0 / pollwake (3)
From
Hello,

syzbot found the following crash on:

HEAD commit: 245a4300 Merge branch 'rcu/kcsan' into tip/locking/kcsan
git tree: https://github.com/google/ktsan.git kcsan
console output: https://syzkaller.appspot.com/x/log.txt?x=11beba8ee00000
kernel config: https://syzkaller.appspot.com/x/.config?x=a38292766f8efdaa
dashboard link: https://syzkaller.appspot.com/bug?extid=9b3fb64bcc8c1d807595
compiler: gcc (GCC) 9.0.0 20181231 (experimental)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+9b3fb64bcc8c1d807595@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in poll_schedule_timeout.constprop.0 / pollwake

write to 0xffffc90001043c30 of 4 bytes by task 17695 on cpu 0:
__pollwake fs/select.c:197 [inline]
pollwake+0xe3/0x140 fs/select.c:217
__wake_up_common+0x7b/0x180 kernel/sched/wait.c:93
__wake_up_common_lock+0x77/0xb0 kernel/sched/wait.c:123
__wake_up+0xe/0x10 kernel/sched/wait.c:142
signalfd_notify include/linux/signalfd.h:22 [inline]
signalfd_notify include/linux/signalfd.h:19 [inline]
__send_signal+0x70e/0x870 kernel/signal.c:1158
send_signal+0x224/0x2b0 kernel/signal.c:1236
__group_send_sig_info kernel/signal.c:1275 [inline]
do_notify_parent+0x55b/0x5e0 kernel/signal.c:1992
exit_notify kernel/exit.c:670 [inline]
do_exit+0x16ef/0x18c0 kernel/exit.c:818
do_group_exit+0xb4/0x1c0 kernel/exit.c:895
__do_sys_exit_group kernel/exit.c:906 [inline]
__se_sys_exit_group kernel/exit.c:904 [inline]
__x64_sys_exit_group+0x2e/0x30 kernel/exit.c:904
do_syscall_64+0xcc/0x3a0 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffffc90001043c30 of 4 bytes by task 15995 on cpu 1:
poll_schedule_timeout.constprop.0+0x50/0xc0 fs/select.c:242
do_poll fs/select.c:951 [inline]
do_sys_poll+0x66d/0x990 fs/select.c:1001
__do_sys_poll fs/select.c:1059 [inline]
__se_sys_poll fs/select.c:1047 [inline]
__x64_sys_poll+0x10f/0x250 fs/select.c:1047
do_syscall_64+0xcc/0x3a0 arch/x86/entry/common.c:294
entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 15995 Comm: udevd Not tainted 5.5.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
==================================================================


---
This bug is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzkaller@googlegroups.com.

syzbot will keep track of this bug report. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

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