syzbot


KCSAN: data-race in __stop_tty / n_tty_receive_char (9)

Status: moderation: reported on 2025/06/23 22:28
Subsystems: serial
[Documentation on labels]
Reported-by: syzbot+f60b1045feb8aa408859@syzkaller.appspotmail.com
First crash: 52d, last: 4d12h
Similar bugs (8)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KCSAN: data-race in __stop_tty / n_tty_receive_char (7) serial 6 1 374d 374d 0/29 auto-obsoleted due to no activity on 2024/09/10 06:07
upstream KCSAN: data-race in __stop_tty / n_tty_receive_char (5) serial 6 4 700d 736d 0/29 auto-obsoleted due to no activity on 2023/10/20 07:37
upstream KCSAN: data-race in __stop_tty / n_tty_receive_char (6) serial 6 17 411d 568d 0/29 auto-obsoleted due to no activity on 2024/08/04 08:07
upstream KCSAN: data-race in __stop_tty / n_tty_receive_char (8) serial 6 7 132d 215d 0/29 auto-obsoleted due to no activity on 2025/05/31 03:59
upstream KCSAN: data-race in __stop_tty / n_tty_receive_char (4) serial 6 2 1044d 1049d 0/29 auto-obsoleted due to no activity on 2022/11/10 02:34
upstream KCSAN: data-race in __stop_tty / n_tty_receive_char (3) serial 6 1 1133d 1133d 0/29 auto-closed as invalid on 2022/08/13 02:09
upstream KCSAN: data-race in __stop_tty / n_tty_receive_char (2) serial 6 2 1223d 1231d 0/29 auto-closed as invalid on 2022/05/15 01:17
upstream KCSAN: data-race in __stop_tty / n_tty_receive_char serial 6 1 1417d 1417d 0/29 auto-closed as invalid on 2021/11/01 13:40

Sample crash report:
==================================================================
BUG: KCSAN: data-race in __stop_tty / n_tty_receive_char

write to 0xffff88810387c1bc of 1 bytes by task 6913 on cpu 1:
 __stop_tty+0x36/0x90 drivers/tty/tty_io.c:744
 n_tty_ioctl_helper+0x1e9/0x210 drivers/tty/tty_ioctl.c:951
 n_tty_ioctl+0x101/0x200 drivers/tty/n_tty.c:2509
 tty_ioctl+0x842/0xb80 drivers/tty/tty_io.c:2801
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:598 [inline]
 __se_sys_ioctl+0xcb/0x140 fs/ioctl.c:584
 __x64_sys_ioctl+0x43/0x50 fs/ioctl.c:584
 x64_sys_call+0x1816/0x2ff0 arch/x86/include/generated/asm/syscalls_64.h:17
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd2/0x200 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88810387c1bc of 1 bytes by task 278 on cpu 0:
 n_tty_receive_char+0x3d/0x6a0 drivers/tty/n_tty.c:1411
 n_tty_receive_buf_standard+0x473/0x2f10 drivers/tty/n_tty.c:1590
 __receive_buf drivers/tty/n_tty.c:1624 [inline]
 n_tty_receive_buf_common+0x805/0xbe0 drivers/tty/n_tty.c:1723
 n_tty_receive_buf2+0x33/0x40 drivers/tty/n_tty.c:1769
 tty_ldisc_receive_buf+0x63/0xf0 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+0x148/0x340 drivers/tty/tty_buffer.c:495
 process_one_work kernel/workqueue.c:3236 [inline]
 process_scheduled_works+0x4cb/0x9d0 kernel/workqueue.c:3319
 worker_thread+0x582/0x770 kernel/workqueue.c:3400
 kthread+0x489/0x510 kernel/kthread.c:463
 ret_from_fork+0xda/0x150 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

value changed: 0x00 -> 0x01

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 278 Comm: kworker/u8:5 Not tainted 6.17.0-rc1-syzkaller #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
Workqueue: events_unbound flush_to_ldisc
==================================================================

Crashes (3):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/08/10 23:36 upstream 8f5ae30d69d7 32a0e5ed .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __stop_tty / n_tty_receive_char
2025/07/29 01:32 upstream 038d61fd6422 6654ea9c .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __stop_tty / n_tty_receive_char
2025/06/23 22:27 upstream 86731a2a651e e2f27c35 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __stop_tty / n_tty_receive_char
* Struck through repros no longer work on HEAD.