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KCSAN: data-race in __stop_tty / pty_write (16)

Status: moderation: reported on 2025/12/27 04:05
Subsystems: serial
[Documentation on labels]
Reported-by: syzbot+9c3ef9da49a12d7bbc27@syzkaller.appspotmail.com
First crash: 75d, last: 38d
▶ ▼ ✨ AI Jobs (2)
ID Workflow Result Correct Bug Created Started Finished Revision Error
e8a9d68b-3db4-4e66-a3df-1abbef210f10 repro 💥 KCSAN: data-race in __stop_tty / pty_write (16) 2026/03/09 22:34 2026/03/09 22:34 2026/03/09 22:57 6972f30219093b03bcc1a54487e12a7097245c01 Error 504, Message: Deadline expired before operation could complete., Status: DEADLINE_EXCEEDED, Details: [map[@type:type.googleapis.com/google.rpc.DebugInfo detail:[ORIGINAL ERROR] generic::deadline_exceeded: [original: beyond::dependency::DEADLINE_EXCEEDED] while running coroutine; Failed while fetching a stream from leaf at '<bns:/bns/mh/borg/mh/bns/uniserve-model-server-common-prod-jobs/uniserve.prod-common-mh.prod-common-global.ghostlite_pod-16x16.d25843e7-34fd-4991-a772-fc875026757d/128>'; Failed to close the streaming context; status = DEADLINE_EXCEEDED: while running coroutine; Failed while fetching a stream from leaf at '<bns:/bns/mh/borg/mh/bns/uniserve-model-server-common-prod-jobs/uniserve.prod-common-mh.prod-common-global.ghostlite_pod-16x16.d25843e7-34fd-4991-a772-fc875026757d/128>' [type.googleapis.com/stairways.orch.ErrorLoc='learning/serving/servables/wiz/orch_wiz_servable.cc:1077'] === Source Location Trace: === net/rpc/common/stream/stream-context.cc:1470 learning/brain/research/stairways/orchestrator/root/remote_chain.cc:150 learning/serving/servables/wiz/orch_wiz_servable.cc:1085 ; Failed to run inference for model: go/debugstr name: "prod-common-global__/aistudio/gemini-v4p1m-rev24-snowball-lc__main__/aistudio/gemini-v4p1m-rev24-snowball-lc__2026022700__prefill__variant__c3238ed4-cb0b-41c1-a7f5-a73f3b419975" version { value: 1 } signature_name: "serving_default" ; [model=/aistudio/gemini-v4p1m-rev24-snowball-lc,target=PredictionService]; for endpoint: [google.rpc.error_details_ext] { message: "Deadline expired before operation could complete." details { type_url: "type.googleapis.com/language_labs.genai.debug.GeminiApiDebugInfo" value: "\222\001\375\t\n\335\twhile running coroutine; Failed while fetching a stream from leaf at \'<bns:/bns/mh/borg/mh/bns/uniserve-model-server-common-prod-jobs/uniserve.prod-common-mh.prod-common-global.ghostlite_pod-16x16.d25843e7-34fd-4991-a772-fc875026757d/128>\'; Failed to close the streaming context; status = DEADLINE_EXCEEDED: while running coroutine; Failed while fetching a stream from leaf at \'<bns:/bns/mh/borg/mh/bns/uniserve-model-server-common-prod-jobs/uniserve.prod-common-mh.prod-common-global.ghostlite_pod-16x16.d25843e7-34fd-4991-a772-fc875026757d/128>\' [type.googleapis.com/stairways.orch.ErrorLoc=\'learning/serving/servables/wiz/orch_wiz_servable.cc:1077\']\n=== Source Location Trace: ===\nnet/rpc/common/stream/stream-context.cc:1470\nlearning/brain/research/stairways/orchestrator/root/remote_chain.cc:150\nlearning/serving/servables/wiz/orch_wiz_servable.cc:1085\n; Failed to run inference for model: go/debugstr \nname: \"prod-common-global__/aistudio/gemini-v4p1m-rev24-snowball-lc__main__/aistudio/gemini-v4p1m-rev24-snowball-lc__2026022700__prefill__variant__c3238ed4-cb0b-41c1-a7f5-a73f3b419975\"\nversion {\n value: 1\n}\nsignature_name: \"serving_default\"\n; [model=/aistudio/gemini-v4p1m-rev24-snowball-lc,target=PredictionService]; for endpoint: \022\033net/rpc/rpc-status.cc:562:0" } } 525002922 { 3 { 1: "/aistudio/gemini-v4p1m-rev24-snowball-lc" } 6 { 5 { 1 { 1: "/aistudio/gemini-v4p1m-rev24-snowball-lc" 3: "serving_default" } 2: 1048576 3: 1 } 6 { 2: 1 3: 0 4: "Non-retryable error: while running coroutine; Failed while fetching a stream from leaf at \'<bns:/bns/mh/borg/mh/bns/uniserve-model-server-common-prod-jobs/uniserve.prod-common-mh.prod-common-global.ghostlite_pod-16x16.d25843e7-34fd-4991-a772-fc875026757d/128>\'; Failed to close the streaming context; status = DEADLINE_EXCEEDED: while running coroutine; Failed while fetching a stream from leaf at \'<bns:/bns/mh/borg/mh/bns/uniserve-model-server-common-prod-jobs/uniserve.prod-common-mh.prod-common-global.ghostlite_pod-16x16.d25843e7-34fd-4991-a772-fc875026757d/128>\' [type.googleapis.com/stairways.orch.ErrorLoc=\'learning/serving/servables/wiz/orch_wiz_servable.cc:1077\']\n=== Source Location Trace: ===\nnet/rpc/common/stream/stream-context.cc:1470\nlearning/brain/research/stairways/orchestrator/root/remote_chain.cc:150\nlearning/serving/servables/wiz/orch_wiz_servable.cc:1085\n
4f8bda19-d56a-49f6-879d-185e0fb1c438 assessment-kcsan Benign: ✅  ❓ KCSAN: data-race in __stop_tty / pty_write (16) 2026/01/10 08:14 2026/01/10 08:14 2026/01/10 08:38 7519916073b761ced56a7b15fdeeb4674e8dc125
▶ ▼ Similar bugs (15)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KCSAN: data-race in __stop_tty / pty_write serial 6 1 1701d 1701d 0/29 auto-closed as invalid on 2021/08/19 13:20
upstream KCSAN: data-race in __stop_tty / pty_write (6) serial 6 1 1394d 1394d 0/29 auto-closed as invalid on 2022/06/22 11:40
upstream KCSAN: data-race in __stop_tty / pty_write (8) serial 6 4 1054d 1070d 0/29 auto-obsoleted due to no activity on 2023/05/28 07:29
upstream KCSAN: data-race in __stop_tty / pty_write (9) serial 6 3 964d 994d 0/29 auto-obsoleted due to no activity on 2023/08/26 21:27
upstream KCSAN: data-race in __stop_tty / pty_write (2) serial 6 1 1619d 1619d 0/29 auto-closed as invalid on 2021/11/09 20:04
upstream KCSAN: data-race in __stop_tty / pty_write (4) serial 6 1 1491d 1491d 0/29 auto-closed as invalid on 2022/03/17 12:14
upstream KCSAN: data-race in __stop_tty / pty_write (3) serial 6 1 1578d 1578d 0/29 auto-closed as invalid on 2021/12/20 07:00
upstream KCSAN: data-race in __stop_tty / pty_write (13) serial 6 19 544d 722d 0/29 auto-obsoleted due to no activity on 2024/10/19 22:07
upstream KCSAN: data-race in __stop_tty / pty_write (5) serial 6 1 1447d 1447d 0/29 auto-closed as invalid on 2022/04/30 10:57
upstream KCSAN: data-race in __stop_tty / pty_write (10) serial 6 1 915d 915d 0/29 auto-obsoleted due to no activity on 2023/10/14 11:29
upstream KCSAN: data-race in __stop_tty / pty_write (11) serial 6 3 872d 874d 0/29 auto-obsoleted due to no activity on 2023/11/26 18:07
upstream KCSAN: data-race in __stop_tty / pty_write (14) serial 6 1 505d 505d 0/29 auto-obsoleted due to no activity on 2024/12/18 17:29
upstream KCSAN: data-race in __stop_tty / pty_write (12) serial 6 7 759d 820d 0/29 auto-obsoleted due to no activity on 2024/03/18 19:09
upstream KCSAN: data-race in __stop_tty / pty_write (7) serial 6 1 1253d 1253d 0/29 auto-obsoleted due to no activity on 2022/11/10 14:49
upstream KCSAN: data-race in __stop_tty / pty_write (15) serial 6 12 213d 446d 0/29 auto-obsoleted due to no activity on 2025/10/05 23:38

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

write to 0xffff888112056dbc of 1 bytes by task 6116 on cpu 1:
 __stop_tty+0x36/0x90 drivers/tty/tty_io.c:744
 n_tty_ioctl_helper+0x2d1/0x370 drivers/tty/tty_ioctl.c:951
 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+0x14b0/0x3000 arch/x86/include/generated/asm/syscalls_64.h:17
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xc0/0x2a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff888112056dbc of 1 bytes by task 2044 on cpu 0:
 pty_write+0x24/0x90 drivers/tty/pty.c:113
 tty_put_char+0x8f/0xc0 drivers/tty/tty_io.c:3154
 n_tty_process_echo_ops drivers/tty/n_tty.c:643 [inline]
 __process_echoes+0x2f9/0x6b0 drivers/tty/n_tty.c:689
 flush_echoes drivers/tty/n_tty.c:785 [inline]
 __receive_buf drivers/tty/n_tty.c:1618 [inline]
 n_tty_receive_buf_common+0x918/0xc10 drivers/tty/n_tty.c:1715
 n_tty_receive_buf2+0x33/0x40 drivers/tty/n_tty.c:1759
 tty_ldisc_receive_buf+0x66/0xf0 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:3257 [inline]
 process_scheduled_works+0x4cd/0x9d0 kernel/workqueue.c:3340
 worker_thread+0x6bc/0x8b0 kernel/workqueue.c:3421
 kthread+0x488/0x510 kernel/kthread.c:463
 ret_from_fork+0x148/0x280 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246

value changed: 0x00 -> 0x01

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 2044 Comm: kworker/u8:6 Not tainted syzkaller #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Workqueue: events_unbound flush_to_ldisc
==================================================================

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/02/02 01:57 upstream 9f2693489ef8 6b8752f2 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __stop_tty / pty_write
2025/12/27 04:04 upstream 3f0e9c8cefa9 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __stop_tty / pty_write
* Struck through repros no longer work on HEAD.