[moderation] [serial?] KCSAN: data-race in n_tty_poll / tty_set_termios (9)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 183601b78a9b Merge tag 'perf-urgent-2025-03-22' of git://g..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1013be98580000
kernel config: https://syzkaller.appspot.com/x/.config?x=f33d372c4021745
dashboard link: https://syzkaller.appspot.com/bug?extid=4771cf9a20cb6de82abc
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/6d2392821840/disk-183601b7.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/1b1da65c67ea/vmlinux-183601b7.xz
kernel image: https://storage.googleapis.com/syzbot-assets/8907683660b6/bzImage-183601b7.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+4771cf...@syzkaller.appspotmail.com

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

read-write to 0xffff8881186f4d14 of 4 bytes by task 3772 on cpu 1:
unset_locked_termios drivers/tty/tty_ioctl.c:217 [inline]
tty_set_termios+0x1a2/0x8b0 drivers/tty/tty_ioctl.c:340
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:2811
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:906 [inline]
__se_sys_ioctl+0xc9/0x140 fs/ioctl.c:892
__x64_sys_ioctl+0x43/0x50 fs/ioctl.c:892
x64_sys_call+0x1690/0x2dc0 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 0xffff8881186f4d14 of 4 bytes by task 3767 on cpu 0:
input_available_p drivers/tty/n_tty.c:1939 [inline]
n_tty_poll+0x2b9/0x4b0 drivers/tty/n_tty.c:2468
tty_poll+0x78/0xf0 drivers/tty/tty_io.c:2208
vfs_poll include/linux/poll.h:82 [inline]
__io_arm_poll_handler+0x1e5/0xd50 io_uring/poll.c:582
io_poll_add+0x6b/0xf0 io_uring/poll.c:892
io_issue_sqe+0x15f/0xb70 io_uring/io_uring.c:1737
io_queue_sqe io_uring/io_uring.c:1947 [inline]
io_submit_sqe io_uring/io_uring.c:2204 [inline]
io_submit_sqes+0x680/0x1070 io_uring/io_uring.c:2321
__do_sys_io_uring_enter io_uring/io_uring.c:3372 [inline]
__se_sys_io_uring_enter+0x1c0/0x1b00 io_uring/io_uring.c:3307
__x64_sys_io_uring_enter+0x78/0x90 io_uring/io_uring.c:3307
x64_sys_call+0xb5e/0x2dc0 arch/x86/include/generated/asm/syscalls_64.h:427
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

value changed: 0x00008a3b -> 0x00000fff

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 3767 Comm: syz.4.9761 Not tainted 6.14.0-rc7-syzkaller-00202-g183601b78a9b #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
==================================================================


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[syzbot]

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