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

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 86c4d58a99ab Merge tag 'for-linus-iommufd' of git://git.ke..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1228c407e80000
kernel config: https://syzkaller.appspot.com/x/.config?x=fba13658254d98c5
dashboard link: https://syzkaller.appspot.com/bug?extid=69b06d495ab3fa1db867
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/ea096ab752ff/disk-86c4d58a.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/1627df201d3b/vmlinux-86c4d58a.xz
kernel image: https://storage.googleapis.com/syzbot-assets/70af53538f2a/bzImage-86c4d58a.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+69b06d...@syzkaller.appspotmail.com

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

read-write to 0xffff88818e5d1da8 of 4 bytes by task 6669 on cpu 0:
tty_reopen+0x10c/0x1b0 drivers/tty/tty_io.c:1371
tty_open_by_driver drivers/tty/tty_io.c:2082 [inline]
tty_open+0x8f4/0xb00 drivers/tty/tty_io.c:2135
chrdev_open+0x322/0x390 fs/char_dev.c:414
do_dentry_open+0x635/0xbd0 fs/open.c:953
vfs_open+0x4a/0x50 fs/open.c:1087
do_open fs/namei.c:3641 [inline]
path_openat+0x1819/0x1d30 fs/namei.c:3798
do_filp_open+0xf6/0x200 fs/namei.c:3825
do_sys_openat2+0xab/0x110 fs/open.c:1404
do_sys_open fs/open.c:1419 [inline]
__do_sys_openat fs/open.c:1435 [inline]
__se_sys_openat fs/open.c:1430 [inline]
__x64_sys_openat+0xf3/0x120 fs/open.c:1430
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0x59/0x120 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x63/0x6b

read to 0xffff88818e5d1da8 of 4 bytes by task 6663 on cpu 1:
n_tty_write+0x321/0xb60 drivers/tty/n_tty.c:2373
iterate_tty_write drivers/tty/tty_io.c:1021 [inline]
file_tty_write+0x382/0x680 drivers/tty/tty_io.c:1096
tty_write+0x28/0x30 drivers/tty/tty_io.c:1117
call_write_iter include/linux/fs.h:2085 [inline]
new_sync_write fs/read_write.c:497 [inline]
vfs_write+0x48a/0x790 fs/read_write.c:590
ksys_write+0xeb/0x1a0 fs/read_write.c:643
__do_sys_write fs/read_write.c:655 [inline]
__se_sys_write fs/read_write.c:652 [inline]
__x64_sys_write+0x42/0x50 fs/read_write.c:652
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0x59/0x120 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x63/0x6b

value changed: 0x00000001 -> 0x00000002

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 6663 Comm: syz-executor.2 Not tainted 6.7.0-syzkaller-11889-g86c4d58a99ab #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/17/2023
==================================================================


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