[moderation] [serial?] KCSAN: data-race in n_tty_poll / tty_set_termios (6)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 5c24e4e9e708 Merge tag 'hid-for-linus-2024020101' of git:/..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=114478c0180000
kernel config: https://syzkaller.appspot.com/x/.config?x=4aab723d3dfffc44
dashboard link: https://syzkaller.appspot.com/bug?extid=3419ff8d88a24e6515cb
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
CC: [gre...@linuxfoundation.org jiri...@kernel.org linux-...@vger.kernel.org linux-...@vger.kernel.org]

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/939a791831ca/disk-5c24e4e9.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/0ffa996f3841/vmlinux-5c24e4e9.xz
kernel image: https://storage.googleapis.com/syzbot-assets/00a87458e25f/bzImage-5c24e4e9.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+3419ff...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in n_tty_poll / tty_set_termios

write to 0xffff888137e6a91e of 1 bytes by task 5945 on cpu 1:
unset_locked_termios drivers/tty/tty_ioctl.c:220 [inline]
tty_set_termios+0x3a4/0x8a0 drivers/tty/tty_ioctl.c:340
set_termios+0x47e/0x4c0 drivers/tty/tty_ioctl.c:516
tty_mode_ioctl+0x391/0x5d0
n_tty_ioctl_helper+0x8d/0x240 drivers/tty/tty_ioctl.c:986
n_tty_ioctl+0xfd/0x200 drivers/tty/n_tty.c:2511
tty_ioctl+0x875/0xbc0 drivers/tty/tty_io.c:2812
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:871 [inline]
__se_sys_ioctl+0xcf/0x140 fs/ioctl.c:857
__x64_sys_ioctl+0x43/0x50 fs/ioctl.c:857
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xcd/0x1d0 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x63/0x6b

read to 0xffff888137e6a91e of 1 bytes by task 9 on cpu 0:
input_available_p drivers/tty/n_tty.c:1927 [inline]
n_tty_poll+0x217/0x490 drivers/tty/n_tty.c:2458
tty_poll+0x7b/0xf0 drivers/tty/tty_io.c:2214
vfs_poll include/linux/poll.h:88 [inline]
p9_fd_poll net/9p/trans_fd.c:237 [inline]
p9_poll_mux net/9p/trans_fd.c:629 [inline]
p9_poll_workfn+0x1e9/0x410 net/9p/trans_fd.c:1178
process_one_work kernel/workqueue.c:2633 [inline]
process_scheduled_works+0x5b8/0xa40 kernel/workqueue.c:2706
worker_thread+0x525/0x730 kernel/workqueue.c:2787
kthread+0x1d7/0x210 kernel/kthread.c:388
ret_from_fork+0x48/0x60 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:242

value changed: 0x79 -> 0xf2

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 9 Comm: kworker/0:1 Not tainted 6.8.0-rc2-syzkaller-00084-g5c24e4e9e708 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/25/2024
Workqueue: events p9_poll_workfn
==================================================================


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.