[moderation] [serial?] KCSAN: data-race in n_tty_receive_char / n_tty_write (8)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 6efbea77b390 Merge tag 'arm64-fixes' of git://git.kernel.o..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=10c0c240580000
kernel config: https://syzkaller.appspot.com/x/.config?x=fd83253b74c9c570
dashboard link: https://syzkaller.appspot.com/bug?extid=42a0b6a4eb0bccdfaf51
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/7ca5e21d3173/disk-6efbea77.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/93e50178b43f/vmlinux-6efbea77.xz
kernel image: https://storage.googleapis.com/syzbot-assets/583dce1edf07/bzImage-6efbea77.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+42a0b6...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in n_tty_receive_char / n_tty_write

write to 0xffffc9001a983028 of 8 bytes by task 1272 on cpu 1:
commit_echoes drivers/tty/n_tty.c:758 [inline]
n_tty_receive_char+0x4c4/0x680 drivers/tty/n_tty.c:1437
n_tty_receive_buf_standard+0x4bd/0x2e30 drivers/tty/n_tty.c:1606
__receive_buf drivers/tty/n_tty.c:1640 [inline]
n_tty_receive_buf_common+0x83a/0xbe0 drivers/tty/n_tty.c:1739
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

read to 0xffffc9001a983028 of 8 bytes by task 14554 on cpu 0:
process_echoes drivers/tty/n_tty.c:784 [inline]
n_tty_write+0x15c/0xb80 drivers/tty/n_tty.c:2375
iterate_tty_write drivers/tty/tty_io.c:1015 [inline]
file_tty_write+0x37a/0x680 drivers/tty/tty_io.c:1090
tty_write+0x28/0x30 drivers/tty/tty_io.c:1111
new_sync_write fs/read_write.c:590 [inline]
vfs_write+0x76a/0x910 fs/read_write.c:683
ksys_write+0xeb/0x1b0 fs/read_write.c:736
__do_sys_write fs/read_write.c:748 [inline]
__se_sys_write fs/read_write.c:745 [inline]
__x64_sys_write+0x42/0x50 fs/read_write.c:745
x64_sys_call+0x27dd/0x2d60 arch/x86/include/generated/asm/syscalls_64.h:2
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: 0x0000000000000007 -> 0x0000000000000008

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 14554 Comm: syz.0.2495 Not tainted 6.12.0-rc3-syzkaller-00183-g6efbea77b390 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
==================================================================


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[syzbot]

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