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

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 3f82f1c3a036 Merge tag 'x86-urgent-2023-12-23' of git://gi..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=10307ba5e80000
kernel config: https://syzkaller.appspot.com/x/.config?x=989a728d0f884055
dashboard link: https://syzkaller.appspot.com/bug?extid=5afd85ad30347ff96848
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/3eb84945c63c/disk-3f82f1c3.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/5753c8502e10/vmlinux-3f82f1c3.xz
kernel image: https://storage.googleapis.com/syzbot-assets/7d8e1a249332/bzImage-3f82f1c3.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+5afd85...@syzkaller.appspotmail.com

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

write to 0xffff888135fd7922 of 1 bytes by task 8201 on cpu 1:
unset_locked_termios drivers/tty/tty_ioctl.c:220 [inline]
tty_set_termios+0x4c8/0x8a0 drivers/tty/tty_ioctl.c:340
set_termios+0x47e/0x4c0 drivers/tty/tty_ioctl.c:516
tty_mode_ioctl+0x3e1/0x590
ppp_asynctty_ioctl+0x21d/0x2e0 drivers/net/ppp/ppp_async.c:323
tty_ioctl+0x875/0xbc0 drivers/tty/tty_io.c:2789
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+0x44/0x110 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x63/0x6b

read to 0xffff888135fd7922 of 1 bytes by task 21326 on cpu 0:
ppp_async_input drivers/net/ppp/ppp_async.c:903 [inline]
ppp_asynctty_receive+0x872/0x1040 drivers/net/ppp/ppp_async.c:341
tty_ldisc_receive_buf+0xcc/0xe0 drivers/tty/tty_buffer.c:390
tty_port_default_receive_buf+0x59/0x90 drivers/tty/tty_port.c:37
receive_buf drivers/tty/tty_buffer.c:444 [inline]
flush_to_ldisc+0x1ca/0x400 drivers/tty/tty_buffer.c:494
process_one_work kernel/workqueue.c:2627 [inline]
process_scheduled_works+0x5b8/0xa30 kernel/workqueue.c:2700
worker_thread+0x525/0x730 kernel/workqueue.c:2781
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: 0x13 -> 0x51

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 21326 Comm: kworker/u4:0 Not tainted 6.7.0-rc6-syzkaller-00303-g3f82f1c3a036 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/17/2023
Workqueue: events_unbound flush_to_ldisc
==================================================================


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[syzbot]

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