[moderation] [serial?] KCSAN: data-race in ppp_asynctty_receive / tty_set_termios (7)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: e6f39a90de92 Merge tag 'efi-fixes-for-v6.8-1' of git://git..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1282bfa2180000
kernel config: https://syzkaller.appspot.com/x/.config?x=3cd0dc1b46a5bc5c
dashboard link: https://syzkaller.appspot.com/bug?extid=ef7ff586ea286b061516
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/b03303eeb2c2/disk-e6f39a90.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/72c5ffb55217/vmlinux-e6f39a90.xz
kernel image: https://storage.googleapis.com/syzbot-assets/281fcd2e60f4/bzImage-e6f39a90.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+ef7ff5...@syzkaller.appspotmail.com

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

write to 0xffff88813769c922 of 1 bytes by task 8402 on cpu 0:
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+0x391/0x5d0
ppp_asynctty_ioctl+0x21d/0x2e0 drivers/net/ppp/ppp_async.c:323
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 0xffff88813769c922 of 1 bytes by task 7685 on cpu 1:
ppp_async_input drivers/net/ppp/ppp_async.c:907 [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: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: 0x13 -> 0x19

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 7685 Comm: kworker/u4:26 Not tainted 6.8.0-rc3-syzkaller-00215-ge6f39a90de92 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/25/2024
Workqueue: events_unbound flush_to_ldisc
==================================================================


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