KCSAN: data-race in n_tty_poll / tty_set_termios (10)

Status: auto-obsoleted due to no activity on 2026/06/18 06:12
Subsystems: serial
Labels: prio:low
[Documentation on labels]
Reported-by: syzbot+9e777dfa1bd5e087c7c8@syzkaller.appspotmail.com
First crash: 140d, last: 114d
▶ ▼ ✨ AI Jobs (2)
ID Workflow Result Correct Bug Created Started Finished Revision
937f32ba assessment-security DenialOfService: ❌ Exploitable: ❌ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ❌ RemoteTrigger: ❌ Unprivileged: ✅ UserNamespace: ✅ VMGuestTrigger: ❌ VMHostTrigger: ❌ ❓ KCSAN: data-race in n_tty_poll / tty_set_termios (10) 2026/05/23 22:11 2026/05/23 22:11 2026/05/23 22:51 c69befb3
61794981 assessment-kcsan Benign: ✅ Confident: ✅ ❓ KCSAN: data-race in n_tty_poll / tty_set_termios (10) 2026/03/28 10:00 2026/03/28 10:00 2026/03/28 10:25 356bdfc9
▶ ▼ Similar bugs (9)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KCSAN: data-race in n_tty_poll / tty_set_termios (4) serial 6 1 1678d 1678d 0/29 auto-closed as invalid on 2022/02/14 10:19
upstream KCSAN: data-race in n_tty_poll / tty_set_termios (6) serial 6 1 925d 925d 0/29 auto-obsoleted due to no activity on 2024/03/08 03:04
upstream KCSAN: data-race in n_tty_poll / tty_set_termios (8) serial 6 2 606d 614d 0/29 auto-obsoleted due to no activity on 2025/02/11 05:59
upstream KCSAN: data-race in n_tty_poll / tty_set_termios (2) serial 6 2 1869d 1903d 0/29 auto-closed as invalid on 2021/08/07 13:54
upstream KCSAN: data-race in n_tty_poll / tty_set_termios (7) serial 6 1 749d 749d 0/29 auto-obsoleted due to no activity on 2024/08/31 07:27
upstream KCSAN: data-race in n_tty_poll / tty_set_termios serial 6 1 1946d 1946d 0/29 auto-closed as invalid on 2021/05/22 11:20
upstream KCSAN: data-race in n_tty_poll / tty_set_termios (5) serial 6 1 1068d 1068d 0/29 auto-obsoleted due to no activity on 2023/10/17 08:33
upstream KCSAN: data-race in n_tty_poll / tty_set_termios (9) serial 6 7 437d 510d 0/29 auto-obsoleted due to no activity on 2025/07/30 04:01
upstream KCSAN: data-race in n_tty_poll / tty_set_termios (3) serial 6 1 1759d 1759d 0/29 auto-closed as invalid on 2021/11/25 02:42

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

write to 0xffff8881339794e0 of 44 bytes by task 14156 on cpu 0:
 tty_set_termios+0xc0/0x910 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+0x101/0x220 drivers/tty/n_tty.c:2496
 tty_ioctl+0x83e/0xb80 drivers/tty/tty_io.c:2801
 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+0x1563/0x3020 arch/x86/include/generated/asm/syscalls_64.h:17
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x12c/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff8881339794f6 of 1 bytes by task 14150 on cpu 1:
 input_available_p drivers/tty/n_tty.c:1910 [inline]
 n_tty_poll+0xba/0x450 drivers/tty/n_tty.c:2440
 tty_poll+0x79/0xf0 drivers/tty/tty_io.c:2199
 vfs_poll include/linux/poll.h:82 [inline]
 __io_arm_poll_handler+0x1ef/0xbf0 io_uring/poll.c:588
 io_arm_apoll+0x2eb/0x400 io_uring/poll.c:696
 io_arm_poll_handler+0x12f/0x160 io_uring/poll.c:725
 io_queue_async+0x25d/0x320 io_uring/io_uring.c:1617
 io_queue_sqe io_uring/io_uring.c:1643 [inline]
 io_submit_sqe io_uring/io_uring.c:1922 [inline]
 io_submit_sqes+0xb02/0x1170 io_uring/io_uring.c:2045
 __do_sys_io_uring_enter io_uring/io_uring.c:2634 [inline]
 __se_sys_io_uring_enter+0x255/0xfb0 io_uring/io_uring.c:2583
 __x64_sys_io_uring_enter+0x78/0x90 io_uring/io_uring.c:2583
 x64_sys_call+0x1e16/0x3020 arch/x86/include/generated/asm/syscalls_64.h:427
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x12c/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00 -> 0x24

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 14150 Comm: syz.9.3062 Tainted: G        W           syzkaller #0 PREEMPT(full) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026
==================================================================

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/04/23 06:11 upstream 2a4c0c11c019 b10da5ec .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in n_tty_poll / tty_set_termios
2026/03/28 10:00 upstream 7df48e363130 356bdfc9 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in n_tty_poll / tty_set_termios
* Struck through repros no longer work on HEAD.