syzbot


KCSAN: data-race in n_tty_lookahead_flow_ctrl / tty_set_termios (5)

Status: moderation: reported on 2026/02/01 03:27
Subsystems: serial
[Documentation on labels]
Reported-by: syzbot+0479f67e520e4910d370@syzkaller.appspotmail.com
First crash: 40d, last: 1d10h
✨ AI Jobs (2)
ID Workflow Result Correct Bug Created Started Finished Revision Error
263d9c0a-7e70-40bf-ba40-a027aabd9159 repro KCSAN: data-race in n_tty_lookahead_flow_ctrl / tty_set_termios (5) 2026/03/06 10:15 2026/03/06 10:15 2026/03/06 10:17 31e9c887f7dc24e04b3ca70d0d54fc34141844b0
9e1237a4-4420-4cd8-a11c-61dcfb9f8241 assessment-kcsan Benign: ✅  Confident: ✅  KCSAN: data-race in n_tty_lookahead_flow_ctrl / tty_set_termios (5) 2026/02/01 03:26 2026/02/01 03:26 2026/02/01 03:52 63a5f77ffe6c631f8781efb082e741722cdf8c6a+
Similar bugs (4)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KCSAN: data-race in n_tty_lookahead_flow_ctrl / tty_set_termios (4) serial 6 1 708d 708d 0/29 auto-obsoleted due to no activity on 2024/05/09 07:47
upstream KCSAN: data-race in n_tty_lookahead_flow_ctrl / tty_set_termios (3) serial 6 1 781d 781d 0/29 auto-obsoleted due to no activity on 2024/02/26 02:18
upstream KCSAN: data-race in n_tty_lookahead_flow_ctrl / tty_set_termios (2) serial 6 1 957d 957d 0/29 auto-obsoleted due to no activity on 2023/09/02 17:23
upstream KCSAN: data-race in n_tty_lookahead_flow_ctrl / tty_set_termios serial 6 52 1140d 1310d 0/29 auto-obsoleted due to no activity on 2023/04/08 10:34

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

write to 0xffff88812ff44d08 of 44 bytes by task 17407 on cpu 0:
 tty_set_termios+0xc0/0x910 drivers/tty/tty_ioctl.c:335
 set_termios+0x4a7/0x4f0 drivers/tty/tty_ioctl.c:512
 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+0x101/0x230 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/0x370 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88812ff44d21 of 1 bytes by task 30 on cpu 1:
 n_tty_is_char_flow_ctrl drivers/tty/n_tty.c:1196 [inline]
 n_tty_receive_char_flow_ctrl drivers/tty/n_tty.c:1217 [inline]
 n_tty_lookahead_flow_ctrl+0x126/0x300 drivers/tty/n_tty.c:1492
 tty_port_default_lookahead_buf+0x91/0xc0 drivers/tty/tty_port.c:59
 lookahead_bufs drivers/tty/tty_buffer.c:428 [inline]
 flush_to_ldisc+0x288/0x340 drivers/tty/tty_buffer.c:498
 process_one_work kernel/workqueue.c:3275 [inline]
 process_scheduled_works+0x4de/0x9e0 kernel/workqueue.c:3358
 worker_thread+0x581/0x770 kernel/workqueue.c:3439
 kthread+0x22a/0x280 kernel/kthread.c:436
 ret_from_fork+0x150/0x360 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

value changed: 0x11 -> 0x77

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 30 Comm: kworker/u8:1 Tainted: G        W           syzkaller #0 PREEMPT(full) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
Workqueue: events_unbound flush_to_ldisc
==================================================================

Crashes (33):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/03/12 00:53 upstream b29fb8829bff 2d88ab01 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in n_tty_lookahead_flow_ctrl / tty_set_termios
2026/03/11 13:40 upstream b4f0dd314b39 86914af9 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in n_tty_lookahead_flow_ctrl / tty_set_termios
2026/03/10 10:44 upstream 1f318b96cc84 6972f302 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in n_tty_lookahead_flow_ctrl / tty_set_termios
2026/03/07 22:42 upstream 4ae12d8bd9a8 5cb44a80 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in n_tty_lookahead_flow_ctrl / tty_set_termios
2026/03/07 08:05 upstream 651690480a96 5cb44a80 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in n_tty_lookahead_flow_ctrl / tty_set_termios
2026/03/06 06:26 upstream 5ee8dbf54602 31e9c887 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in n_tty_lookahead_flow_ctrl / tty_set_termios
2026/03/04 07:59 upstream 0031c06807cf 4180d919 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in n_tty_lookahead_flow_ctrl / tty_set_termios
2026/03/02 05:46 upstream 39c633261414 43249bac .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in n_tty_lookahead_flow_ctrl / tty_set_termios
2026/03/01 13:51 upstream eb71ab2bf722 43249bac .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in n_tty_lookahead_flow_ctrl / tty_set_termios
2026/02/28 22:53 upstream 2f9339c052bd 43249bac .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in n_tty_lookahead_flow_ctrl / tty_set_termios
2026/02/28 02:47 upstream a75cb869a8cc 2cf092b8 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in n_tty_lookahead_flow_ctrl / tty_set_termios
2026/02/26 21:14 upstream f4d0ec0aa20d ffa54287 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in n_tty_lookahead_flow_ctrl / tty_set_termios
2026/02/25 11:09 upstream 7dff99b35460 94a9671e .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in n_tty_lookahead_flow_ctrl / tty_set_termios
2026/02/25 01:43 upstream 7dff99b35460 787dfb7c .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in n_tty_lookahead_flow_ctrl / tty_set_termios
2026/02/24 20:34 upstream 7dff99b35460 96b1aa46 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in n_tty_lookahead_flow_ctrl / tty_set_termios
2026/02/23 18:56 upstream 6de23f81a5e0 6beca497 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in n_tty_lookahead_flow_ctrl / tty_set_termios
2026/02/23 18:55 upstream 6de23f81a5e0 6beca497 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in n_tty_lookahead_flow_ctrl / tty_set_termios
2026/02/19 03:29 upstream 23b0f90ba871 77d4d919 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in n_tty_lookahead_flow_ctrl / tty_set_termios
2026/02/17 12:20 upstream 970296997869 e439b951 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in n_tty_lookahead_flow_ctrl / tty_set_termios
2026/02/15 21:35 upstream ca4ee40bf13d 1e62d198 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in n_tty_lookahead_flow_ctrl / tty_set_termios
2026/02/15 02:38 upstream 3e48a11675c5 1e62d198 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in n_tty_lookahead_flow_ctrl / tty_set_termios
2026/02/14 05:10 upstream cee73b1e840c 1e62d198 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in n_tty_lookahead_flow_ctrl / tty_set_termios
2026/02/12 19:01 upstream 37a93dd5c49b 504cb1bf .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in n_tty_lookahead_flow_ctrl / tty_set_termios
2026/02/11 09:34 upstream dc855b77719f 441e25b7 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in n_tty_lookahead_flow_ctrl / tty_set_termios
2026/02/10 09:40 upstream 8a5203c630c6 4ab09a02 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in n_tty_lookahead_flow_ctrl / tty_set_termios
2026/02/09 21:35 upstream 05f7e89ab973 df949cd9 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in n_tty_lookahead_flow_ctrl / tty_set_termios
2026/02/09 01:21 upstream e98f34af6116 4c131dc4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in n_tty_lookahead_flow_ctrl / tty_set_termios
2026/02/08 12:31 upstream e7aa57247700 4c131dc4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in n_tty_lookahead_flow_ctrl / tty_set_termios
2026/02/07 18:55 upstream 2687c848e578 4c131dc4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in n_tty_lookahead_flow_ctrl / tty_set_termios
2026/02/07 16:46 upstream 2687c848e578 f20fc9f9 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in n_tty_lookahead_flow_ctrl / tty_set_termios
2026/02/06 01:27 upstream 8fdb05de0e2d f03c4191 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in n_tty_lookahead_flow_ctrl / tty_set_termios
2026/02/01 22:22 upstream 9f2693489ef8 6b8752f2 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in n_tty_lookahead_flow_ctrl / tty_set_termios
2026/02/01 03:26 upstream ad9a728a3388 6b8752f2 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in n_tty_lookahead_flow_ctrl / tty_set_termios
* Struck through repros no longer work on HEAD.