[moderation] [serial?] KCSAN: data-race in n_tty_check_unthrottle / n_tty_receive_buf_common (10)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 0bbac3facb5d Linux 6.9-rc4
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=13be4367180000
kernel config: https://syzkaller.appspot.com/x/.config?x=eaea34ec4c9b6fb6
dashboard link: https://syzkaller.appspot.com/bug?extid=6241e42afd7f404fd187
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/5e85356d4cd6/disk-0bbac3fa.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/9bc6a51e45e8/vmlinux-0bbac3fa.xz
kernel image: https://storage.googleapis.com/syzbot-assets/7a1ec327fc6a/bzImage-0bbac3fa.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+6241e4...@syzkaller.appspotmail.com

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

write to 0xffff8881160d25dc of 4 bytes by task 26211 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+0xf0b/0x11d0 drivers/tty/n_tty.c:2302
iterate_tty_read drivers/tty/tty_io.c:862 [inline]
tty_read+0x15b/0x480 drivers/tty/tty_io.c:937
call_read_iter include/linux/fs.h:2104 [inline]
new_sync_read fs/read_write.c:395 [inline]
vfs_read+0x5bc/0x6b0 fs/read_write.c:476
ksys_read+0xeb/0x1b0 fs/read_write.c:619
__do_sys_read fs/read_write.c:629 [inline]
__se_sys_read fs/read_write.c:627 [inline]
__x64_sys_read+0x42/0x50 fs/read_write.c:627
x64_sys_call+0x27ad/0x2d30 arch/x86/include/generated/asm/syscalls_64.h:1
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+0x77/0x7f

write to 0xffff8881160d25dc of 4 bytes by task 26214 on cpu 1:
n_tty_receive_buf_common+0xae5/0xbd0
n_tty_receive_buf+0x30/0x40 drivers/tty/n_tty.c:1769
tiocsti+0x166/0x1d0 drivers/tty/tty_io.c:2299
tty_ioctl+0x415/0xbe0 drivers/tty/tty_io.c:2717
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:904 [inline]
__se_sys_ioctl+0xd3/0x150 fs/ioctl.c:890
__x64_sys_ioctl+0x43/0x50 fs/ioctl.c:890
x64_sys_call+0x155d/0x2d30 arch/x86/include/generated/asm/syscalls_64.h:17
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+0x77/0x7f

value changed: 0x00000001 -> 0x00000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 26214 Comm: syz-executor.3 Not tainted 6.9.0-rc4-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
==================================================================


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