[moderation] [serial?] KCSAN: data-race in n_tty_check_unthrottle / n_tty_receive_buf_common (12)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: a0e3919a2df2 Merge tag 'usb-6.13-rc3' of git://git.kernel...
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=11aac344580000
kernel config: https://syzkaller.appspot.com/x/.config?x=1fe4854f351e948c
dashboard link: https://syzkaller.appspot.com/bug?extid=c1d36663f7387c500e7f
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/e51dc3ecb78f/disk-a0e3919a.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/1f38219aa6e9/vmlinux-a0e3919a.xz
kernel image: https://storage.googleapis.com/syzbot-assets/fc33b8e12125/bzImage-a0e3919a.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+c1d366...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in n_tty_check_unthrottle / n_tty_receive_buf_common

write to 0xffff888117e3f1dc of 4 bytes by task 4699 on cpu 0:
tty_set_flow_change drivers/tty/tty.h:59 [inline]
n_tty_check_unthrottle+0xd7/0x1c0 drivers/tty/n_tty.c:280
n_tty_read+0xf05/0x11c0 drivers/tty/n_tty.c:2312
iterate_tty_read drivers/tty/tty_io.c:856 [inline]
tty_read+0x155/0x460 drivers/tty/tty_io.c:931
do_iter_readv_writev+0x394/0x450
vfs_readv+0x1df/0x660 fs/read_write.c:1011
do_readv+0xf4/0x220 fs/read_write.c:1073
__do_sys_readv fs/read_write.c:1158 [inline]
__se_sys_readv fs/read_write.c:1155 [inline]
__x64_sys_readv+0x45/0x50 fs/read_write.c:1155
x64_sys_call+0x2c34/0x2dc0 arch/x86/include/generated/asm/syscalls_64.h:20
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

write to 0xffff888117e3f1dc of 4 bytes by task 1955 on cpu 1:
n_tty_receive_buf_common+0xafa/0xbe0
n_tty_receive_buf2+0x33/0x40 drivers/tty/n_tty.c:1785
tty_ldisc_receive_buf+0x63/0x100 drivers/tty/tty_buffer.c:387
tty_port_default_receive_buf+0x59/0x90 drivers/tty/tty_port.c:37
receive_buf drivers/tty/tty_buffer.c:445 [inline]
flush_to_ldisc+0x1ce/0x410 drivers/tty/tty_buffer.c:495
process_one_work kernel/workqueue.c:3229 [inline]
process_scheduled_works+0x483/0x9a0 kernel/workqueue.c:3310
worker_thread+0x51d/0x6f0 kernel/workqueue.c:3391
kthread+0x1d1/0x210 kernel/kthread.c:389
ret_from_fork+0x4b/0x60 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

value changed: 0x00000001 -> 0x00000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 1955 Comm: kworker/u8:7 Not tainted 6.13.0-rc2-syzkaller-00333-ga0e3919a2df2 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
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.