[moderation] [serial?] KCSAN: data-race in n_tty_poll / pty_unix98_ioctl (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: e2291551827f Merge tag 'probes-fixes-v6.16-rc6' of git://g..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=174b1382580000
kernel config: https://syzkaller.appspot.com/x/.config?x=c8b73fe883c5b6ae
dashboard link: https://syzkaller.appspot.com/bug?extid=7c357b50876920ae945d
compiler: Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7
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/9d179aad9ded/disk-e2291551.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/8aeb42e84f31/vmlinux-e2291551.xz
kernel image: https://storage.googleapis.com/syzbot-assets/d70acc96e443/bzImage-e2291551.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+7c357b...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in n_tty_poll / pty_unix98_ioctl

write to 0xffff8881049509d5 of 1 bytes by task 6881 on cpu 1:
pty_set_pktmode drivers/tty/pty.c:-1 [inline]
pty_unix98_ioctl+0x2c0/0x2e0 drivers/tty/pty.c:651
tty_ioctl+0x7db/0xb80 drivers/tty/tty_io.c:2792
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:907 [inline]
__se_sys_ioctl+0xcb/0x140 fs/ioctl.c:893
__x64_sys_ioctl+0x43/0x50 fs/ioctl.c:893
x64_sys_call+0x19a8/0x2fb0 arch/x86/include/generated/asm/syscalls_64.h:17
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xd2/0x200 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff8881049509d5 of 1 bytes by task 6877 on cpu 0:
n_tty_poll+0x31f/0x450 drivers/tty/n_tty.c:2459
tty_poll+0x76/0xf0 drivers/tty/tty_io.c:2199
vfs_poll include/linux/poll.h:82 [inline]
__io_arm_poll_handler+0x1eb/0xb70 io_uring/poll.c:583
io_arm_poll_handler+0x427/0x590 io_uring/poll.c:708
io_queue_async+0x60/0x3a0 io_uring/io_uring.c:1949
io_queue_sqe io_uring/io_uring.c:1975 [inline]
io_submit_sqe io_uring/io_uring.c:2224 [inline]
io_submit_sqes+0xa25/0xfd0 io_uring/io_uring.c:2337
__do_sys_io_uring_enter io_uring/io_uring.c:3404 [inline]
__se_sys_io_uring_enter+0x1c1/0x1b70 io_uring/io_uring.c:3338
__x64_sys_io_uring_enter+0x78/0x90 io_uring/io_uring.c:3338
x64_sys_call+0x28c8/0x2fb0 arch/x86/include/generated/asm/syscalls_64.h:427
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xd2/0x200 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00 -> 0x01

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 6877 Comm: syz.2.1396 Not tainted 6.16.0-rc6-syzkaller-00037-ge2291551827f #0 PREEMPT(voluntary)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
==================================================================


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[syzbot]

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