[moderation] [serial?] KCSAN: data-race in n_tty_poll / n_tty_set_termios (4)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: f23aa4c0761a Merge tag 'hid-for-linus-2024090201' of git:/..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=15c02307980000
kernel config: https://syzkaller.appspot.com/x/.config?x=95098faba89c70c9
dashboard link: https://syzkaller.appspot.com/bug?extid=98be2f82e2f7d41e765d
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/2c64b6482fc7/disk-f23aa4c0.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/acacebac526d/vmlinux-f23aa4c0.xz
kernel image: https://storage.googleapis.com/syzbot-assets/512566ea4d6d/bzImage-f23aa4c0.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+98be2f...@syzkaller.appspotmail.com

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

write to 0xffffc9000e235010 of 8 bytes by task 5528 on cpu 0:
n_tty_set_termios+0x188/0x850 drivers/tty/n_tty.c:1812
tty_set_termios+0x849/0x8b0 drivers/tty/tty_ioctl.c:352
set_termios+0x497/0x4e0 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:2521
tty_ioctl+0x87a/0xbe0 drivers/tty/tty_io.c:2812
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:907 [inline]
__se_sys_ioctl+0xcd/0x140 fs/ioctl.c:893
__x64_sys_ioctl+0x43/0x50 fs/ioctl.c:893
x64_sys_call+0x15cc/0x2d60 arch/x86/include/generated/asm/syscalls_64.h:17
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffffc9000e235010 of 8 bytes by task 5529 on cpu 1:
input_available_p drivers/tty/n_tty.c:1940 [inline]
n_tty_poll+0x2d2/0x490 drivers/tty/n_tty.c:2468
tty_poll+0x78/0xf0 drivers/tty/tty_io.c:2208
vfs_poll include/linux/poll.h:84 [inline]
io_poll_check_events io_uring/poll.c:304 [inline]
io_poll_task_func+0x146/0x8a0 io_uring/poll.c:358
io_handle_tw_list+0xe3/0x200 io_uring/io_uring.c:1060
tctx_task_work_run+0x6c/0x1b0 io_uring/io_uring.c:1132
tctx_task_work+0x40/0x80 io_uring/io_uring.c:1150
task_work_run+0x13a/0x1a0 kernel/task_work.c:228
get_signal+0xee9/0x1070 kernel/signal.c:2690
arch_do_signal_or_restart+0x95/0x4b0 arch/x86/kernel/signal.c:337
exit_to_user_mode_loop kernel/entry/common.c:111 [inline]
exit_to_user_mode_prepare include/linux/entry-common.h:328 [inline]
__syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
syscall_exit_to_user_mode+0x59/0x130 kernel/entry/common.c:218
do_syscall_64+0xd6/0x1c0 arch/x86/entry/common.c:89
entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x0000000000000000 -> 0x0000000000000fff

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 5529 Comm: syz.3.400 Not tainted 6.12.0-rc1-syzkaller-00042-gf23aa4c0761a #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
==================================================================


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[syzbot]

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