KCSAN: data-race in n_tty_write / tty_set_termios (15)

Status: moderation: reported on 2026/10/15 03:28
Subsystems: serial
Labels: race:benign
[Documentation on labels]
Reported-by: syzbot+5f0cc119dbc35181707a@syzkaller.appspotmail.com
First crash: 9h24m, last: 9h24m
▶ ▼ ✨ AI Jobs (1)
ID Workflow Result Correct Bug Created Started Finished Revision
04faaef5 assessment-kcsan Benign: ✅ ❓ KCSAN: data-race in n_tty_write / tty_set_termios (15) 2026/10/15 03:27 2026/10/15 03:28 2026/10/15 04:07 8fb0ae89
▶ ▼ Similar bugs (14)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KCSAN: data-race in n_tty_write / tty_set_termios (3) serial 6 1 2177d 2177d 0/29 auto-closed as invalid on 2020/12/02 18:50
upstream KCSAN: data-race in n_tty_write / tty_set_termios (10) serial 6 1 1274d 1274d 0/29 auto-obsoleted due to no activity on 2023/05/24 17:53
upstream KCSAN: data-race in n_tty_write / tty_set_termios (8) serial 6 9 1518d 1644d 0/29 auto-closed as invalid on 2022/09/22 18:33
upstream KCSAN: data-race in n_tty_write / tty_set_termios (4) serial 6 3 2086d 2136d 0/29 auto-closed as invalid on 2021/03/04 08:49
upstream KCSAN: data-race in n_tty_write / tty_set_termios (12) serial 6 34 509d 684d 0/29 auto-obsoleted due to no activity on 2025/07/18 20:44
upstream KCSAN: data-race in n_tty_write / tty_set_termios (13) serial 6 2 412d 448d 0/29 auto-obsoleted due to no activity on 2025/10/24 12:51
upstream KCSAN: data-race in n_tty_write / tty_set_termios (2) serial 6 1 2242d 2242d 0/29 auto-closed as invalid on 2020/09/29 07:57
upstream KCSAN: data-race in n_tty_write / tty_set_termios (6) serial 6 8 1804d 1923d 0/29 auto-closed as invalid on 2021/12/10 21:01
upstream KCSAN: data-race in n_tty_write / tty_set_termios (11) serial 6 3 843d 848d 0/29 auto-obsoleted due to no activity on 2024/07/29 01:08
upstream KCSAN: data-race in n_tty_write / tty_set_termios (14) serial 6 12 277d 350d 0/29 auto-obsoleted due to no activity on 2026/03/07 20:59
upstream KCSAN: data-race in n_tty_write / tty_set_termios (5) serial 6 2 1975d 1977d 0/29 auto-closed as invalid on 2021/06/22 15:42
upstream KCSAN: data-race in n_tty_write / tty_set_termios serial 6 1 2304d 2304d 0/29 auto-closed as invalid on 2020/07/29 04:13
upstream KCSAN: data-race in n_tty_write / tty_set_termios (7) serial 6 4 1686d 1724d 0/29 auto-closed as invalid on 2022/04/07 21:37
upstream KCSAN: data-race in n_tty_write / tty_set_termios (9) serial 6 7 1365d 1446d 0/29 auto-obsoleted due to no activity on 2023/02/26 21:46

Sample crash report:
==================================================================
BUG: KCSAN: data-race in n_tty_write / tty_set_termios

write to 0xffff88811aa110e0 of 44 bytes by task 15952 on cpu 0:
 tty_set_termios+0xc0/0x900 drivers/tty/tty_ioctl.c:335
 set_termios+0x373/0x4f0 drivers/tty/tty_ioctl.c:516
 tty_mode_ioctl+0x37f/0x5b0 drivers/tty/tty_ioctl.c:-1
 n_tty_ioctl_helper+0x87/0x370 drivers/tty/tty_ioctl.c:982
 n_tty_ioctl+0x101/0x200 drivers/tty/n_tty.c:2496
 tty_ioctl+0x83e/0xb80 drivers/tty/tty_io.c:2791
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:597 [inline]
 __se_sys_ioctl+0xce/0x140 fs/ioctl.c:583
 __x64_sys_ioctl+0x43/0x50 fs/ioctl.c:583
 x64_sys_call+0x239d/0x2550 arch/x86/include/generated/asm/syscalls_64.h:17
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x112/0x360 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88811aa110ec of 4 bytes by task 15957 on cpu 1:
 n_tty_write+0xc8/0xb00 drivers/tty/n_tty.c:2343
 iterate_tty_write drivers/tty/tty_io.c:1008 [inline]
 file_tty_write+0x392/0x6a0 drivers/tty/tty_io.c:1056
 tty_write+0x25/0x30 drivers/tty/tty_io.c:1077
 io_write+0x615/0xcf0 io_uring/rw.c:1178
 __io_issue_sqe+0xfd/0x2e0 io_uring/io_uring.c:1388
 io_issue_sqe+0x1e7/0xb80 io_uring/io_uring.c:1411
 io_queue_sqe io_uring/io_uring.c:1642 [inline]
 io_submit_sqe io_uring/io_uring.c:1927 [inline]
 io_submit_sqes+0x7e1/0x1180 io_uring/io_uring.c:2050
 __do_sys_io_uring_enter io_uring/io_uring.c:2640 [inline]
 __se_sys_io_uring_enter+0x25c/0xf90 io_uring/io_uring.c:2589
 __x64_sys_io_uring_enter+0x78/0x90 io_uring/io_uring.c:2589
 x64_sys_call+0x1780/0x2550 arch/x86/include/generated/asm/syscalls_64.h:427
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x112/0x360 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00008a3b -> 0x00000004

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 15957 Comm: syz.6.13406 Not tainted syzkaller #0 PREEMPT(lazy) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2026
==================================================================

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/10/15 03:27 upstream 0fcb05b72344 8fb0ae89 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in n_tty_write / tty_set_termios
* Struck through repros no longer work on HEAD.