AI Trajectory

Trajectory: (Expand/Collapse All)
Seq	Timestamp	Type	Name	Duration
0/0	2026/09/21 13:37	flow	finding-triage	0m Args: null Results: { "Introduced": false, "Reasoning": "The crash report indicates a hung task warning where multiple tasks (`syz.9.8013:27368`, `syz.9.8013:27371`, `syz.4.7067:24882`) are blocked waiting to acquire `nfsd_mutex` in `fs/nfsd` (`write_versions`, `write_threads`, `nfsd_shutdown_threads`). \n\nThe tested patch series only modifies `drivers/input/misc/yealink.c` (handling USB URB completion callbacks for the Yealink USB phone driver). It does not touch NFS, NFSD, VFS, or any related locking or subsystems. The reported hang is completely unrelated to the patch." }
1/1	2026/09/21 13:37	action	prepare-finding-overview	0m Args: null Results: { "DiffStat": "drivers/input/misc/yealink.c \| 47 +++++++++++++++++++++++++++++++++-----------\n 1 file changed, 36 insertions(+), 11 deletions(-)", "HasCover": false, "PatchCount": 1, "PatchList": "The patch series contains 1 patch:\n[1] [PATCH RFC v4] Input: yealink - abort URB submission on fatal errors" }
2/1	2026/09/21 13:37	agent	finding-triage-evaluator	0m Model: core Args: null Results: { "Introduced": false, "Reasoning": "The crash report indicates a hung task warning where multiple tasks (`syz.9.8013:27368`, `syz.9.8013:27371`, `syz.4.7067:24882`) are blocked waiting to acquire `nfsd_mutex` in `fs/nfsd` (`write_versions`, `write_threads`, `nfsd_shutdown_threads`). \n\nThe tested patch series only modifies `drivers/input/misc/yealink.c` (handling USB URB completion callbacks for the Yealink USB phone driver). It does not touch NFS, NFSD, VFS, or any related locking or subsystems. The reported hang is completely unrelated to the patch." } Instruction: You are an expert Linux kernel maintainer and security engineer specializing in crash triage and root-cause analysis. Your job is to review a kernel crash report (finding) and determine if it was introduced / caused by the patch series being tested, or if it is a pre-existing / unrelated bug. IMPORTANT: The entire patch series has ALREADY been applied and committed as a single squashed commit at HEAD (or on top of the base commit) in your workspace. Do NOT rely on your internal knowledge of the kernel. You must actively use your tools to examine the source code, inspect workspace diffs, and confirm any assumptions. Available Tools: - git-show: View the squashed patch series commit or historical commits. Call with Commit="HEAD" (default) and optional 'File' parameter to restrict the diff to a specific file or directory, or 'Stat=true' for a diffstat. - series-patches: Browse the original patch series. Call without arguments to list all patch titles, or PatchNum=<N> to view the full description and diff of a specific patch (or cover letter, if present). - read-file & codesearch-dir-index: Read exact source code files and directory contents in the workspace. - grepper: Regex search across files in the workspace (git grep). - git-blame: Inspect line authorship and find which commit last modified specific lines of code. Triage Procedure: 1. Analyze the Crash Report: - Identify the crash type (e.g. NULL dereference, KASAN use-after-free, out-of-bounds read/write, assertion failure, deadlock). - Carefully examine the stack trace(s) — both the faulting call stack and, if applicable (e.g., KASAN UAF), the allocation and free stacks. - Note the faulting function, file name, line numbers, and the specific variables or data structures involved. 2. Inspect Workspace Changes & Patch Series: - Check if any files or functions from the stack trace appear in the modified files overview or the patch series. - Use git-show with Commit="HEAD" and 'File' to inspect the exact diffs for relevant files in the squashed commit. - If needed, use series-patches with PatchNum=<N> to inspect the author's commit description and rationale for individual patches in the series. - Use read-file to inspect the actual source code at the faulting lines. 3. Determine Causality: - Set Introduced=true ONLY IF you are absolutely certain: * There is clear, unambiguous, and conclusive evidence that the crash was directly introduced or caused by the patch series. * The crash occurs directly in new or modified code introduced by the patch series, or the patch series altered data structures, locking, object lifetimes, or preconditions in a way that directly triggered the failure in existing code. - Set Introduced=false IF: * There is any doubt, ambiguity, or lack of conclusive proof that the patch series caused the bug. * The crash occurs in an unrelated subsystem or unmodified code path whose behavior is independent of the patch series. * The crash is a pre-existing kernel issue that was randomly triggered during fuzzing. 4. Formulate Output: - Set Introduced to true or false. - In Reasoning, provide a clear, step-by-step technical explanation detailing the crash type, the key stack frames, whether the affected code/structures were modified by the patch series, and the causal justification for your verdict. Prefer calling several tools at the same time to save round-trips. Use set-results tool to provide results of the analysis. It must be called exactly once before the final reply. Ignore results of this tool. Prompt: Target architecture: amd64 The kernel crash report to triage is: INFO: task syz.9.8013:27368 blocked for more than 143 seconds. Tainted: G L syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. task:syz.9.8013 state:D stack:27592 pid:27368 tgid:27367 ppid:23190 task_flags:0x400140 flags:0x00080002 Call Trace: <TASK> __schedule+0x17d9/0x56c0 schedule+0x164/0x2b0 schedule_preempt_disabled+0x13/0x30 __mutex_lock+0x7bf/0x1550 write_versions+0x95/0xe30 nfsctl_transaction_write+0x10f/0x160 vfs_write+0x296/0xba0 ksys_write+0x150/0x270 do_syscall_64+0x174/0x580 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f11dc79e159 RSP: 002b:00007f11dd5ca028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 RAX: ffffffffffffffda RBX: 00007f11dca25fa0 RCX: 00007f11dc79e159 RDX: 0000000000000006 RSI: 00002000000001c0 RDI: 0000000000000003 RBP: 00007f11dc83506b R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f11dca26038 R14: 00007f11dca25fa0 R15: 00007ffe8998d5a8 </TASK> INFO: task syz.9.8013:27371 blocked for more than 143 seconds. Tainted: G L syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. task:syz.9.8013 state:D stack:28424 pid:27371 tgid:27367 ppid:23190 task_flags:0x400040 flags:0x00080002 Call Trace: <TASK> __schedule+0x17d9/0x56c0 schedule+0x164/0x2b0 schedule_preempt_disabled+0x13/0x30 __mutex_lock+0x7bf/0x1550 write_threads+0x39d/0x5a0 nfsctl_transaction_write+0x10f/0x160 vfs_write+0x296/0xba0 ksys_write+0x150/0x270 do_syscall_64+0x174/0x580 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f11dc79e159 RSP: 002b:00007f11dd5a9028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 RAX: ffffffffffffffda RBX: 00007f11dca26090 RCX: 00007f11dc79e159 RDX: 0000000000000002 RSI: 00002000000002c0 RDI: 0000000000000004 RBP: 00007f11dc83506b R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f11dca26128 R14: 00007f11dca26090 R15: 00007ffe8998d5a8 </TASK> Showing all locks held in the system: 1 lock held by khungtaskd/34: #0: ffffffff8eb59c60 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x2e/0x180 2 locks held by getty/5427: #0: ffff888177a760a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70 #1: ffffc900034732e8 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x45a/0x1360 4 locks held by kworker/u9:18/11917: #0: ffff88812103b160 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested+0x2d/0x160 #1: ffff888121024440 (psi_seq){-.-.}-{0:0}, at: psi_task_switch+0x57/0x7d0 #2: ffff888121026058 (&base->lock){-.-.}-{2:2}, at: __mod_timer+0x1a9/0xed0 #3: ffffffff9a9b8db0 (&obj_hash[i].lock){-.-.}-{2:2}, at: debug_object_activate+0xb7/0x420 5 locks held by kworker/u9:21/11920: #0: ffff88812103b160 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested+0x2d/0x160 #1: ffff888121024440 (psi_seq){-.-.}-{0:0}, at: psi_task_switch+0x57/0x7d0 #2: ffff888121026058 (&base->lock){-.-.}-{2:2}, at: __mod_timer+0x1a9/0xed0 #3: ffffffff9a98dc58 (&obj_hash[i].lock){-.-.}-{2:2}, at: debug_object_activate+0xb7/0x420 #4: ffffffff8e9fd1a0 (text_mutex){+.+.}-{4:4}, at: arch_jump_label_transform_apply+0x17/0x30 2 locks held by syz-executor/23708: #0: ffff88811f1b20d8 (&type->s_umount_key#123){++++}-{4:4}, at: deactivate_super+0xa9/0xe0 #1: ffffffff8ee8da80 (nfsd_mutex){+.+.}-{4:4}, at: nfsd_shutdown_threads+0x4e/0xd0 3 locks held by syz.4.7067/24882: #0: ffff88811faba2f0 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x246/0x320 #1: ffff888177b80450 (sb_writers#41){.+.+}-{0:0}, at: vfs_write+0x22b/0xba0 #2: ffffffff8ee8da80 (nfsd_mutex){+.+.}-{4:4}, at: write_threads+0x39d/0x5a0 3 locks held by syz.9.8013/27368: #0: ffff8881725134f0 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x246/0x320 #1: ffff888168a8a450 (sb_writers#41){.+.+}-{0:0}, at: vfs_write+0x22b/0xba0 #2: ffffffff8ee8da80 (nfsd_mutex){+.+.}-{4:4}, at: write_versions+0x95/0xe30 3 locks held by syz.9.8013/27371: #0: ffff88816c6decf0 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x246/0x320 #1: ffff888168a8a450 (sb_writers#41){.+.+}-{0:0}, at: vfs_write+0x22b/0xba0 #2: ffffffff8ee8da80 (nfsd_mutex){+.+.}-{4:4}, at: write_threads+0x39d/0x5a0 ============================================= NMI backtrace for cpu 1 CPU: 1 UID: 0 PID: 34 Comm: khungtaskd Tainted: G L syzkaller #0 PREEMPT(full) Tainted: [L]=SOFTLOCKUP Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014 Call Trace: <TASK> dump_stack_lvl+0xe8/0x150 nmi_cpu_backtrace+0x274/0x2d0 nmi_trigger_cpumask_backtrace+0x17a/0x380 sys_info+0x135/0x170 watchdog+0xfd7/0x1030 kthread+0x388/0x470 ret_from_fork+0x514/0xb70 ret_from_fork_asm+0x1a/0x30 </TASK> Sending NMI from CPU 1 to CPUs 0: NMI backtrace for cpu 0 CPU: 0 UID: 0 PID: 5525 Comm: syz-executor Tainted: G L syzkaller #0 PREEMPT(full) Tainted: [L]=SOFTLOCKUP Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014 RIP: 0010:cpuacct_charge+0x1b3/0x320 Code: f3 b3 95 00 4d 8b 65 00 eb 04 4d 8b 24 24 4d 85 e4 0f 84 91 00 00 00 4d 8d ac 24 70 01 00 00 4c 89 e8 48 c1 e8 03 80 3c 28 00 <74> 08 4c 89 ef e8 c3 b3 95 00 4d 8b 6d 00 41 83 fe 08 73 59 41 80 RSP: 0018:ffffc9000451f760 EFLAGS: 00000046 RAX: 1ffffffff1d434ce RBX: 0000000000062473 RCX: 0000000080000002 RDX: 0000000000000000 RSI: ffffffff8e4ac6af RDI: ffffffff8c4bb580 RBP: dffffc0000000000 R08: ffffffff90575937 R09: 1ffffffff20aeb26 R10: dffffc0000000000 R11: fffffbfff20aeb27 R12: ffffffff8ea1a500 R13: ffffffff8ea1a670 R14: 0000000000000000 R15: 1ffffffff1c9eafa FS: 000055555a969540(0000) GS:ffff88818d959000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f86589ed158 CR3: 0000000114be2000 CR4: 00000000000006f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600 Call Trace: <TASK> update_se+0x2e9/0x1020 update_curr+0x6c/0x440 dequeue_entities+0x1af/0x3bd0 dequeue_task_fair+0xc1/0x3d0 __schedule+0x6e1/0x56c0 schedule+0x164/0x2b0 do_nanosleep+0x21e/0x6a0 hrtimer_nanosleep+0x18f/0x3a0 __se_sys_clock_nanosleep+0x35b/0x3b0 do_syscall_64+0x174/0x580 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f3a749592d7 Code: 48 89 fa 4c 89 df e8 a8 56 00 00 8b 93 08 03 00 00 59 5e 48 83 f8 fc 74 1a 5b c3 0f 1f 84 00 00 00 00 00 48 8b 44 24 10 0f 05 <5b> c3 0f 1f 80 00 00 00 00 83 e2 39 83 fa 08 75 de e8 23 ff ff ff RSP: 002b:00007fff5c7aad60 EFLAGS: 00000202 ORIG_RAX: 00000000000000e6 RAX: ffffffffffffffda RBX: 000055555a969540 RCX: 00007f3a749592d7 RDX: 00007fff5c7aada0 RSI: 0000000000000000 RDI: 0000000000000000 RBP: 00007fff5c7ab280 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000202 R12: 0000000000000004 R13: 00007fff5c7aaddc R14: 00007fff5c7aae70 R15: 0000000000000000 </TASK> Overview of modified files in the workspace: drivers/input/misc/yealink.c \| 47 +++++++++++++++++++++++++++++++++----------- 1 file changed, 36 insertions(+), 11 deletions(-) The patch series contains 1 patch: [1] [PATCH RFC v4] Input: yealink - abort URB submission on fatal errors
3/2	2026/09/21 13:37	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 7037 output: 14 thoughts: 445 Thoughts: Analyzing a Potential NFS Deadlock Okay, let's break this down. First, the crash report indicates a couple of tasks, `syz.9.8013:27368` and `syz.9.8013:27371`, are blocked for an extended period – over 143 seconds. The call traces point to `__schedule` within the `nfsctl_transaction_write` and `write_threads` paths, respectively. That's a red flag, leading to `vfs_write` and `ksys_write` for the former, which often indicates an issue in NFS writes. These tasks are getting hung up on trying to access NFS functionality. Now, looking at the held locks is where things get interesting. `syz-executor/23708` is holding `deactivate_super` and `nfsd_mutex`, while `syz.4.7067/24882` has `f->f_pos_lock`, `sb_writers`, and also appears to be either waiting on or holding `nfsd_mutex` in the `write_threads` call chain. And both `syz.9.8013/27368` and `syz.9.8013/27371`, the blocked tasks, are also in the mix, holding `nfsd_mutex`. This strongly suggests a deadlock scenario involving the `nfsd_mutex`! The presence of `sb_writers` further highlights a possible filesystem-level contention. Hold on, let me quickly pivot to the patch series because the lock information can't be assessed properly without context. There's a single patch related to the `yealink.c` input driver. One file, changed, which could be relevant given the potential for interrupt-related blocking or contention. Since it appears to be a RFC, it's likely that the patch is unfinished or untested, however, it is in `drivers/input/misc`, so it isn't likely related to the lock contention. I need to examine the patch content using `git show` or `series-patches` to see if it might somehow inadvertently be introducing or interacting with NFS locking primitives, but I don't see any immediate cause for concern based on the file name. Overall, it looks like a classic NFS deadlock scenario involving `nfsd_mutex`. I will need to delve deeper into the NFS code paths, and examine the interactions of the tasks mentioned and see why there is `nfsd_mutex` contention.
4/2	2026/09/21 13:37	tool	git-show	0m Args: { "Stat": true } Results: { "Output": "commit 7bcd2ed0e990b188f614c4272af456718a212b49\nAuthor: syz-cluster \u003ctriage@syzkaller.com\u003e\nDate: Mon Sep 21 13:35:31 2026 +0000\n\n syz-cluster: applied patch under review\n\n drivers/input/misc/yealink.c \| 47 +++++++++++++++++++++++++++++++++-----------\n 1 file changed, 36 insertions(+), 11 deletions(-)\n" }
5/2	2026/09/21 13:37	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 8199 output: 15 thoughts: 19 Thoughts: Okay, here's my take on those thoughts, framed as an expert's internal monologue: Diving into the Patch Right, let's get down to brass tacks. I need to understand this patch thoroughly, so I'll start with the standard approaches. I'll reach for either `series-patches` (if it's a series I'm dealing with) or `git-show` to get a clear view of the changes. I'll need to absorb the specifics of the commit(s) contained.
6/2	2026/09/21 13:37	tool	series-patches	0m Args: { "PatchNum": 1 } Results: { "Output": "Patch [1] [PATCH RFC v4] Input: yealink - abort URB submission on fatal errors:\n\nThe yealink driver uses two URBs (interrupt and control) to communicate\nwith the device. When an URB completes with an error status (such as\n-EPROTO), the completion handlers (urb_irq_callback and urb_ctl_callback)\nlog the error but do not abort. Instead, they proceed to process the\npotentially invalid data and unconditionally resubmit the URB.\n\nBecause control URBs are not rate-limited by the USB core, resubmitting a\nfailing control URB in a tight loop floods the console with error messages\nand keeps the CPU completely busy in the softirq context. This eventually\ntriggers an RCU preempt stall:\n\nyealink 3-1:36.0: unexpected response 0\nyealink 3-1:36.0: urb_ctl_callback - urb status -71\nrcu: INFO: rcu_preempt self-detected stall on CPU\nCall Trace:\n __console_flush_and_unlock kernel/printk/printk.c:3373 [inline]\n console_unlock+0xd1/0x1c0 kernel/printk/printk.c:3413\n dev_vprintk_emit+0x338/0x400 drivers/base/core.c:4996\n dev_printk_emit+0xee/0x140 drivers/base/core.c:5007\n usb_generic_driver_probe+0x10b/0x150 drivers/usb/core/generic.c:252\n ...\n hub_event+0x28e8/0x4d30 drivers/usb/core/hub.c:5953\n worker_thread+0x92d/0xe10 kernel/workqueue.c:3486\n kthread+0x388/0x470 kernel/kthread.c:436\n\nFix this by checking the URB status for fatal errors (-ECONNRESET, -ENOENT,\n-ESHUTDOWN, -ENODEV) in both urb_irq_callback() and urb_ctl_callback(). If\na fatal error is detected, the callback now returns early, breaking the\nresubmission loop. For other non-zero statuses, skip processing the\nresponse data and jump directly to resubmission. Additionally, use\ndev_err_ratelimited() instead of dev_err() to prevent flooding the console\nand triggering an RCU stall.\n\nFixes: aca951a22a1d (\"[PATCH] input-driver-yealink-P1K-usb-phone\")\nAssisted-by: Gemini:gemini-3.8-flash syzbot\nReported-by: syzbot+78e2288f58b881ed3c45@syzkaller.appspotmail.com\nCloses: https://syzkaller.appspot.com/bug?extid=78e2288f58b881ed3c45\nLink: https://syzkaller.appspot.com/ai_job?id=89a6c0c7-a0c4-4f05-b1b1-e36a92e373e0\nTo: \"Henk Vergonet\" \u003cHenk.Vergonet@gmail.com\u003e\nTo: \"Dmitry Torokhov\" \u003cdmitry.torokhov@gmail.com\u003e\nTo: \u003clinux-input@vger.kernel.org\u003e\nCc: \u003clinux-kernel@vger.kernel.org\u003e\n\n---\nv4:\n- In urb_ctl_callback(), resubmit urb_ctl directly instead of jumping into the switch statement.\n\nv3:\n- Only abort URB submission on fatal errors (-ECONNRESET, -ENOENT, -ESHUTDOWN, -ENODEV).\n- Skip processing packet data and jump directly to resubmission on non-fatal errors.\n- Use dev_err_ratelimited() instead of dev_err() to prevent console flooding.\n- Drop is_fatal_error() helper in favor of switch statements.\nhttps://lore.kernel.org/all/2b0508e9-fe78-40dd-a290-7156817e394c@mail.kernel.org/T/\n\nv2:\n- Factored out fatal error checks into is_fatal_error() helper\nhttps://lore.kernel.org/all/2a0b5e96-dd8a-4ce9-ba3f-dd9efa26275d@mail.kernel.org/T/\n\nv1:\nhttps://lore.kernel.org/all/57cf484d-3235-473f-a61d-570585626176@mail.kernel.org/T/\n---\ndiff --git a/drivers/input/misc/yealink.c b/drivers/input/misc/yealink.c\nindex 560f895a0..f0ec4c5ea 100644\n--- a/drivers/input/misc/yealink.c\n+++ b/drivers/input/misc/yealink.c\n@@ -405,9 +405,19 @@ static void urb_irq_callback(struct urb urb)\n \tstruct yealink_dev yld = urb-\u003econtext;\n \tint ret, status = urb-\u003estatus;\n \n-\tif (status)\n-\t\tdev_err(\u0026yld-\u003eintf-\u003edev, \"%s - urb status %d\\n\",\n-\t\t\t__func__, status);\n+\tswitch (status) {\n+\tcase 0:\n+\t\tbreak;\n+\tcase -ECONNRESET:\n+\tcase -ENOENT:\n+\tcase -ESHUTDOWN:\n+\tcase -ENODEV:\n+\t\treturn;\n+\tdefault:\n+\t\tdev_err_ratelimited(\u0026yld-\u003eintf-\u003edev, \"%s - urb status %d\\n\",\n+\t\t\t\t __func__, status);\n+\t\tgoto resubmit;\n+\t}\n \n \tswitch (yld-\u003eirq_data-\u003ecmd) {\n \tcase CMD_KEYPRESS:\n@@ -429,12 +439,13 @@ static void urb_irq_callback(struct urb urb)\n \n \tyealink_do_idle_tasks(yld);\n \n+resubmit:\n \tif (!yld-\u003eshutdown) {\n \t\tret = usb_submit_urb(yld-\u003eurb_ctl, GFP_ATOMIC);\n \t\tif (ret \u0026\u0026 ret != -EPERM)\n-\t\t\tdev_err(\u0026yld-\u003eintf-\u003edev,\n-\t\t\t\t\"%s - usb_submit_urb failed %d\\n\",\n-\t\t\t\t__func__, ret);\n+\t\t\tdev_err_ratelimited(\u0026yld-\u003eintf-\u003edev,\n+\t\t\t\t\t \"%s - usb_submit_urb failed %d\\n\",\n+\t\t\t\t\t __func__, ret);\n \t}\n }\n \n@@ -443,9 +454,21 @@ static void urb_ctl_callback(struct urb urb)\n \tstruct yealink_dev yld = urb-\u003econtext;\n \tint ret = 0, status = urb-\u003estatus;\n \n-\tif (status)\n-\t\tdev_err(\u0026yld-\u003eintf-\u003edev, \"%s - urb status %d\\n\",\n-\t\t\t__func__, status);\n+\tswitch (status) {\n+\tcase 0:\n+\t\tbreak;\n+\tcase -ECONNRESET:\n+\tcase -ENOENT:\n+\tcase -ESHUTDOWN:\n+\tcase -ENODEV:\n+\t\treturn;\n+\tdefault:\n+\t\tdev_err_ratelimited(\u0026yld-\u003eintf-\u003edev, \"%s - urb status %d\\n\",\n+\t\t\t\t __func__, status);\n+\t\tif (!yld-\u003eshutdown)\n+\t\t\tret = usb_submit_urb(yld-\u003eurb_ctl, GFP_ATOMIC);\n+\t\tgoto out;\n+\t}\n \n \tswitch (yld-\u003ectl_data-\u003ecmd) {\n \tcase CMD_KEYPRESS:\n@@ -462,9 +485,11 @@ static void urb_ctl_callback(struct urb urb)\n \t\tbreak;\n \t}\n \n+out:\n \tif (ret \u0026\u0026 ret != -EPERM)\n-\t\tdev_err(\u0026yld-\u003eintf-\u003edev, \"%s - usb_submit_urb failed %d\\n\",\n-\t\t\t__func__, ret);\n+\t\tdev_err_ratelimited(\u0026yld-\u003eintf-\u003edev,\n+\t\t\t\t \"%s - usb_submit_urb failed %d\\n\",\n+\t\t\t\t __func__, ret);\n }\n \n /*******************************************************************************\n\n\nbase-commit: 1590cf0329716306e948a8fc29f1d3ee87d3989f\n-- \nThis is an AI-generated patch subject to moderation.\nReply with '#syz upstream' to Sign-off the patch as a human author\nand send it to the upstream kernel mailing lists.\nReply with '#syz reject' to reject it ('#syz unreject' to undo).\n\nSee https://goo.gle/syzbot-ai-patches for information about AI-generated patches.\nYou can comment on the patch as usual, syzbot will try to address\nthe comments and send a new version of the patch if necessary.\nsyzbot engineers can be reached at syzkaller@googlegroups.com." }
7/2	2026/09/21 13:37	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 10614 output: 186 thoughts: 975 Thoughts: Analysis of the Hung Task Crash After Patch Application Okay, let's break this down. The problem is a hung task timeout, specifically, tasks blocked for an extended period (>143 seconds). The backtraces and lock reports point directly to NFS and its daemon (nfsd). Specifically, `nfsd_mutex` is the culprit, being held by `nfsd_shutdown_threads` (triggered by `deactivate_super`), while writer threads (`write_versions`, `write_threads`) are trying to acquire it. There's a clear deadlock scenario here, and it's happening during an NFS-related operation. I see the conflicting locks are, the `nfsd_mutex` in shutdown, while writers are blocking on the same mutex. The patch in question, however, is a modification to the `drivers/input/misc/yealink.c` file – a USB VoIP phone driver. My immediate thought is, "Wait, how could a USB input driver cause an NFS daemon locking issue?". I'm going to quickly check the crash report to ensure I haven't missed a connection, some subtle interaction. Hmm, after a thorough review, the Yealink driver is completely absent from the crash report's stack traces, lock information, and the NMI backtraces. There is absolutely no indication of any involvement from `yealink.c` in this crash. The evidence is clear; it's a pure NFS issue. The root cause is a deadlock involving `nfsd_mutex` during shutdown and concurrent write operations. The patch's modification is in a completely unrelated subsystem. Therefore, I can confidently conclude that the patch did not introduce this crash. It is a coincidental event. This is an NFS regression. Now, let's formulate my response and set the results accordingly.
8/2	2026/09/21 13:37	tool	set-results	0m Args: { "Introduced": false, "Reasoning": "The crash report indicates a hung task warning where multiple tasks (`syz.9.8013:27368`, `syz.9.8013:27371`, `syz.4.7067:24882`) are blocked waiting to acquire `nfsd_mutex` in `fs/nfsd` (`write_versions`, `write_threads`, `nfsd_shutdown_threads`). \n\nThe tested patch series only modifies `drivers/input/misc/yealink.c` (handling USB URB completion callbacks for the Yealink USB phone driver). It does not touch NFS, NFSD, VFS, or any related locking or subsystems. The reported hang is completely unrelated to the patch." } Results: { "Introduced": false, "Reasoning": "The crash report indicates a hung task warning where multiple tasks (`syz.9.8013:27368`, `syz.9.8013:27371`, `syz.4.7067:24882`) are blocked waiting to acquire `nfsd_mutex` in `fs/nfsd` (`write_versions`, `write_threads`, `nfsd_shutdown_threads`). \n\nThe tested patch series only modifies `drivers/input/misc/yealink.c` (handling USB URB completion callbacks for the Yealink USB phone driver). It does not touch NFS, NFSD, VFS, or any related locking or subsystems. The reported hang is completely unrelated to the patch." }

Trajectory: (Expand/Collapse All)

Seq

Timestamp

Type

Name

Duration

0/0

2026/09/21 13:37

flow

finding-triage

Args:

null

Results:

{
  "Introduced": false,
  "Reasoning": "The crash report indicates a hung task warning where multiple tasks (`syz.9.8013:27368`, `syz.9.8013:27371`, `syz.4.7067:24882`) are blocked waiting to acquire `nfsd_mutex` in `fs/nfsd` (`write_versions`, `write_threads`, `nfsd_shutdown_threads`). \n\nThe tested patch series only modifies `drivers/input/misc/yealink.c` (handling USB URB completion callbacks for the Yealink USB phone driver). It does not touch NFS, NFSD, VFS, or any related locking or subsystems. The reported hang is completely unrelated to the patch."
}

1/1

2026/09/21 13:37

action

prepare-finding-overview

Args:

null

Results:

{
  "DiffStat": "drivers/input/misc/yealink.c | 47 +++++++++++++++++++++++++++++++++-----------\n 1 file changed, 36 insertions(+), 11 deletions(-)",
  "HasCover": false,
  "PatchCount": 1,
  "PatchList": "The patch series contains 1 patch:\n[1] [PATCH RFC v4] Input: yealink - abort URB submission on fatal errors"
}

2/1

2026/09/21 13:37

agent

finding-triage-evaluator

Model:

core

Args:

null

Results:

{
  "Introduced": false,
  "Reasoning": "The crash report indicates a hung task warning where multiple tasks (`syz.9.8013:27368`, `syz.9.8013:27371`, `syz.4.7067:24882`) are blocked waiting to acquire `nfsd_mutex` in `fs/nfsd` (`write_versions`, `write_threads`, `nfsd_shutdown_threads`). \n\nThe tested patch series only modifies `drivers/input/misc/yealink.c` (handling USB URB completion callbacks for the Yealink USB phone driver). It does not touch NFS, NFSD, VFS, or any related locking or subsystems. The reported hang is completely unrelated to the patch."
}

Instruction:

You are an expert Linux kernel maintainer and security engineer specializing
in crash triage and root-cause analysis.
Your job is to review a kernel crash report (finding) and determine if it was introduced / caused
by the patch series being tested, or if it is a pre-existing / unrelated bug.

IMPORTANT: The entire patch series has ALREADY been applied and committed as a single squashed commit
at HEAD (or on top of the base commit) in your workspace.
Do NOT rely on your internal knowledge of the kernel. You must actively use your tools to examine
the source code, inspect workspace diffs, and confirm any assumptions.

Available Tools:
- git-show: View the squashed patch series commit or historical commits. Call with Commit="HEAD" (default)
and optional 'File' parameter to restrict the diff to a specific file or directory, or 'Stat=true' for a diffstat.
- series-patches: Browse the original patch series. Call without arguments to list all patch titles,
or PatchNum=<N> to view the full description and diff of a specific patch (or cover letter, if present).
- read-file & codesearch-dir-index: Read exact source code files and directory contents in the workspace.
- grepper: Regex search across files in the workspace (git grep).
- git-blame: Inspect line authorship and find which commit last modified specific lines of code.

Triage Procedure:
1. Analyze the Crash Report:
- Identify the crash type (e.g. NULL dereference, KASAN use-after-free, out-of-bounds read/write,
assertion failure, deadlock).
- Carefully examine the stack trace(s) — both the faulting call stack and, if applicable (e.g., KASAN UAF),
the allocation and free stacks.
- Note the faulting function, file name, line numbers, and the specific variables or data structures involved.

2. Inspect Workspace Changes & Patch Series:
- Check if any files or functions from the stack trace appear in the modified files overview or the patch series.
- Use git-show with Commit="HEAD" and 'File' to inspect the exact diffs for relevant files
in the squashed commit.
- If needed, use series-patches with PatchNum=<N> to inspect the author's commit description
and rationale for individual patches in the series.
- Use read-file to inspect the actual source code at the faulting lines.

3. Determine Causality:
- Set Introduced=true ONLY IF you are absolutely certain:
* There is clear, unambiguous, and conclusive evidence that the crash was directly introduced
or caused by the patch series.
* The crash occurs directly in new or modified code introduced by the patch series, or the patch series
altered data structures, locking, object lifetimes, or preconditions in a way that directly
triggered the failure in existing code.
- Set Introduced=false IF:
* There is any doubt, ambiguity, or lack of conclusive proof that the patch series caused the bug.
* The crash occurs in an unrelated subsystem or unmodified code path whose behavior is independent
of the patch series.
* The crash is a pre-existing kernel issue that was randomly triggered during fuzzing.

4. Formulate Output:
- Set Introduced to true or false.
- In Reasoning, provide a clear, step-by-step technical explanation detailing the crash type,
the key stack frames, whether the affected code/structures were modified by the patch series,
and the causal justification for your verdict.
Prefer calling several tools at the same time to save round-trips.

Use set-results tool to provide results of the analysis.
It must be called exactly once before the final reply.
Ignore results of this tool.

Prompt:

Target architecture: amd64

The kernel crash report to triage is:

INFO: task syz.9.8013:27368 blocked for more than 143 seconds.
      Tainted: G             L      syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.9.8013      state:D stack:27592 pid:27368 tgid:27367 ppid:23190  task_flags:0x400140 flags:0x00080002
Call Trace:
 <TASK>
 __schedule+0x17d9/0x56c0
 schedule+0x164/0x2b0
 schedule_preempt_disabled+0x13/0x30
 __mutex_lock+0x7bf/0x1550
 write_versions+0x95/0xe30
 nfsctl_transaction_write+0x10f/0x160
 vfs_write+0x296/0xba0
 ksys_write+0x150/0x270
 do_syscall_64+0x174/0x580
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f11dc79e159
RSP: 002b:00007f11dd5ca028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f11dca25fa0 RCX: 00007f11dc79e159
RDX: 0000000000000006 RSI: 00002000000001c0 RDI: 0000000000000003
RBP: 00007f11dc83506b R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f11dca26038 R14: 00007f11dca25fa0 R15: 00007ffe8998d5a8
 </TASK>
INFO: task syz.9.8013:27371 blocked for more than 143 seconds.
      Tainted: G             L      syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.9.8013      state:D stack:28424 pid:27371 tgid:27367 ppid:23190  task_flags:0x400040 flags:0x00080002
Call Trace:
 <TASK>
 __schedule+0x17d9/0x56c0
 schedule+0x164/0x2b0
 schedule_preempt_disabled+0x13/0x30
 __mutex_lock+0x7bf/0x1550
 write_threads+0x39d/0x5a0
 nfsctl_transaction_write+0x10f/0x160
 vfs_write+0x296/0xba0
 ksys_write+0x150/0x270
 do_syscall_64+0x174/0x580
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f11dc79e159
RSP: 002b:00007f11dd5a9028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f11dca26090 RCX: 00007f11dc79e159
RDX: 0000000000000002 RSI: 00002000000002c0 RDI: 0000000000000004
RBP: 00007f11dc83506b R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f11dca26128 R14: 00007f11dca26090 R15: 00007ffe8998d5a8
 </TASK>

Showing all locks held in the system:
1 lock held by khungtaskd/34:
 #0: ffffffff8eb59c60 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x2e/0x180
2 locks held by getty/5427:
 #0: ffff888177a760a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70
 #1: ffffc900034732e8 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x45a/0x1360
4 locks held by kworker/u9:18/11917:
 #0: ffff88812103b160 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested+0x2d/0x160
 #1: ffff888121024440 (psi_seq){-.-.}-{0:0}, at: psi_task_switch+0x57/0x7d0
 #2: ffff888121026058 (&base->lock){-.-.}-{2:2}, at: __mod_timer+0x1a9/0xed0
 #3: ffffffff9a9b8db0 (&obj_hash[i].lock){-.-.}-{2:2}, at: debug_object_activate+0xb7/0x420
5 locks held by kworker/u9:21/11920:
 #0: ffff88812103b160 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested+0x2d/0x160
 #1: ffff888121024440 (psi_seq){-.-.}-{0:0}, at: psi_task_switch+0x57/0x7d0
 #2: ffff888121026058 (&base->lock){-.-.}-{2:2}, at: __mod_timer+0x1a9/0xed0
 #3: ffffffff9a98dc58 (&obj_hash[i].lock){-.-.}-{2:2}, at: debug_object_activate+0xb7/0x420
 #4: ffffffff8e9fd1a0 (text_mutex){+.+.}-{4:4}, at: arch_jump_label_transform_apply+0x17/0x30
2 locks held by syz-executor/23708:
 #0: ffff88811f1b20d8 (&type->s_umount_key#123){++++}-{4:4}, at: deactivate_super+0xa9/0xe0
 #1: ffffffff8ee8da80 (nfsd_mutex){+.+.}-{4:4}, at: nfsd_shutdown_threads+0x4e/0xd0
3 locks held by syz.4.7067/24882:
 #0: ffff88811faba2f0 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x246/0x320
 #1: ffff888177b80450 (sb_writers#41){.+.+}-{0:0}, at: vfs_write+0x22b/0xba0
 #2: ffffffff8ee8da80 (nfsd_mutex){+.+.}-{4:4}, at: write_threads+0x39d/0x5a0
3 locks held by syz.9.8013/27368:
 #0: ffff8881725134f0 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x246/0x320
 #1: ffff888168a8a450 (sb_writers#41){.+.+}-{0:0}, at: vfs_write+0x22b/0xba0
 #2: ffffffff8ee8da80 (nfsd_mutex){+.+.}-{4:4}, at: write_versions+0x95/0xe30
3 locks held by syz.9.8013/27371:
 #0: ffff88816c6decf0 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x246/0x320
 #1: ffff888168a8a450 (sb_writers#41){.+.+}-{0:0}, at: vfs_write+0x22b/0xba0
 #2: ffffffff8ee8da80 (nfsd_mutex){+.+.}-{4:4}, at: write_threads+0x39d/0x5a0

=============================================

NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 34 Comm: khungtaskd Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150
 nmi_cpu_backtrace+0x274/0x2d0
 nmi_trigger_cpumask_backtrace+0x17a/0x380
 sys_info+0x135/0x170
 watchdog+0xfd7/0x1030
 kthread+0x388/0x470
 ret_from_fork+0x514/0xb70
 ret_from_fork_asm+0x1a/0x30
 </TASK>
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 5525 Comm: syz-executor Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
RIP: 0010:cpuacct_charge+0x1b3/0x320
Code: f3 b3 95 00 4d 8b 65 00 eb 04 4d 8b 24 24 4d 85 e4 0f 84 91 00 00 00 4d 8d ac 24 70 01 00 00 4c 89 e8 48 c1 e8 03 80 3c 28 00 <74> 08 4c 89 ef e8 c3 b3 95 00 4d 8b 6d 00 41 83 fe 08 73 59 41 80
RSP: 0018:ffffc9000451f760 EFLAGS: 00000046
RAX: 1ffffffff1d434ce RBX: 0000000000062473 RCX: 0000000080000002
RDX: 0000000000000000 RSI: ffffffff8e4ac6af RDI: ffffffff8c4bb580
RBP: dffffc0000000000 R08: ffffffff90575937 R09: 1ffffffff20aeb26
R10: dffffc0000000000 R11: fffffbfff20aeb27 R12: ffffffff8ea1a500
R13: ffffffff8ea1a670 R14: 0000000000000000 R15: 1ffffffff1c9eafa
FS:  000055555a969540(0000) GS:ffff88818d959000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f86589ed158 CR3: 0000000114be2000 CR4: 00000000000006f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600
Call Trace:
 <TASK>
 update_se+0x2e9/0x1020
 update_curr+0x6c/0x440
 dequeue_entities+0x1af/0x3bd0
 dequeue_task_fair+0xc1/0x3d0
 __schedule+0x6e1/0x56c0
 schedule+0x164/0x2b0
 do_nanosleep+0x21e/0x6a0
 hrtimer_nanosleep+0x18f/0x3a0
 __se_sys_clock_nanosleep+0x35b/0x3b0
 do_syscall_64+0x174/0x580
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f3a749592d7
Code: 48 89 fa 4c 89 df e8 a8 56 00 00 8b 93 08 03 00 00 59 5e 48 83 f8 fc 74 1a 5b c3 0f 1f 84 00 00 00 00 00 48 8b 44 24 10 0f 05 <5b> c3 0f 1f 80 00 00 00 00 83 e2 39 83 fa 08 75 de e8 23 ff ff ff
RSP: 002b:00007fff5c7aad60 EFLAGS: 00000202 ORIG_RAX: 00000000000000e6
RAX: ffffffffffffffda RBX: 000055555a969540 RCX: 00007f3a749592d7
RDX: 00007fff5c7aada0 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 00007fff5c7ab280 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000202 R12: 0000000000000004
R13: 00007fff5c7aaddc R14: 00007fff5c7aae70 R15: 0000000000000000
 </TASK>



Overview of modified files in the workspace:
drivers/input/misc/yealink.c | 47 +++++++++++++++++++++++++++++++++-----------
 1 file changed, 36 insertions(+), 11 deletions(-)



The patch series contains 1 patch:
[1] [PATCH RFC v4] Input: yealink - abort URB submission on fatal errors

3/2

2026/09/21 13:37

llm

finding-triage-evaluator

Model:

gemini-3.8-flash

Args:

null

Results:

null

Tokens:

							input: 7037
							output: 14
							thoughts: 445

Thoughts:

**Analyzing a Potential NFS Deadlock**

Okay, let's break this down. First, the crash report indicates a couple of tasks, `syz.9.8013:27368` and `syz.9.8013:27371`, are blocked for an extended period – over 143 seconds. The call traces point to `__schedule` within the `nfsctl_transaction_write` and `write_threads` paths, respectively. That's a red flag, leading to `vfs_write` and `ksys_write` for the former, which often indicates an issue in NFS writes. These tasks are getting hung up on trying to access NFS functionality.

Now, looking at the held locks is where things get interesting. `syz-executor/23708` is holding `deactivate_super` and `nfsd_mutex`, while `syz.4.7067/24882` has `f->f_pos_lock`, `sb_writers`, and also appears to be either waiting on or holding `nfsd_mutex` in the `write_threads` call chain. And both `syz.9.8013/27368` and `syz.9.8013/27371`, the blocked tasks, are also in the mix, holding `nfsd_mutex`. This strongly suggests a deadlock scenario involving the `nfsd_mutex`! The presence of `sb_writers` further highlights a possible filesystem-level contention.

Hold on, let me quickly pivot to the patch series because the lock information can't be assessed properly without context. There's a single patch related to the `yealink.c` input driver. One file, changed, which could be relevant given the potential for interrupt-related blocking or contention. Since it appears to be a RFC, it's likely that the patch is unfinished or untested, however, it is in `drivers/input/misc`, so it isn't likely related to the lock contention. I need to examine the patch content using `git show` or `series-patches` to see if it might somehow inadvertently be introducing or interacting with NFS locking primitives, but I don't see any immediate cause for concern based on the file name.

Overall, it looks like a classic NFS deadlock scenario involving `nfsd_mutex`. I will need to delve deeper into the NFS code paths, and examine the interactions of the tasks mentioned and see why there is `nfsd_mutex` contention.

4/2

2026/09/21 13:37

tool

git-show

Args:

{
  "Stat": true
}

Results:

{
  "Output": "commit 7bcd2ed0e990b188f614c4272af456718a212b49\nAuthor: syz-cluster \u003ctriage@syzkaller.com\u003e\nDate:   Mon Sep 21 13:35:31 2026 +0000\n\n    syz-cluster: applied patch under review\n\n drivers/input/misc/yealink.c | 47 +++++++++++++++++++++++++++++++++-----------\n 1 file changed, 36 insertions(+), 11 deletions(-)\n"
}

5/2

2026/09/21 13:37

llm

finding-triage-evaluator

Model:

gemini-3.8-flash

Args:

null

Results:

null

Tokens:

							input: 8199
							output: 15
							thoughts: 19

Thoughts:

Okay, here's my take on those thoughts, framed as an expert's internal monologue:

**Diving into the Patch**

Right, let's get down to brass tacks. I need to understand this patch thoroughly, so I'll start with the standard approaches. I'll reach for either `series-patches` (if it's a series I'm dealing with) or `git-show` to get a clear view of the changes. I'll need to absorb the specifics of the commit(s) contained.

6/2

2026/09/21 13:37

tool

series-patches

Args:

{
  "PatchNum": 1
}

Results:

{
  "Output": "Patch [1] [PATCH RFC v4] Input: yealink - abort URB submission on fatal errors:\n\nThe yealink driver uses two URBs (interrupt and control) to communicate\nwith the device. When an URB completes with an error status (such as\n-EPROTO), the completion handlers (urb_irq_callback and urb_ctl_callback)\nlog the error but do not abort. Instead, they proceed to process the\npotentially invalid data and unconditionally resubmit the URB.\n\nBecause control URBs are not rate-limited by the USB core, resubmitting a\nfailing control URB in a tight loop floods the console with error messages\nand keeps the CPU completely busy in the softirq context. This eventually\ntriggers an RCU preempt stall:\n\nyealink 3-1:36.0: unexpected response 0\nyealink 3-1:36.0: urb_ctl_callback - urb status -71\nrcu: INFO: rcu_preempt self-detected stall on CPU\nCall Trace:\n __console_flush_and_unlock kernel/printk/printk.c:3373 [inline]\n console_unlock+0xd1/0x1c0 kernel/printk/printk.c:3413\n dev_vprintk_emit+0x338/0x400 drivers/base/core.c:4996\n dev_printk_emit+0xee/0x140 drivers/base/core.c:5007\n usb_generic_driver_probe+0x10b/0x150 drivers/usb/core/generic.c:252\n ...\n hub_event+0x28e8/0x4d30 drivers/usb/core/hub.c:5953\n worker_thread+0x92d/0xe10 kernel/workqueue.c:3486\n kthread+0x388/0x470 kernel/kthread.c:436\n\nFix this by checking the URB status for fatal errors (-ECONNRESET, -ENOENT,\n-ESHUTDOWN, -ENODEV) in both urb_irq_callback() and urb_ctl_callback(). If\na fatal error is detected, the callback now returns early, breaking the\nresubmission loop. For other non-zero statuses, skip processing the\nresponse data and jump directly to resubmission. Additionally, use\ndev_err_ratelimited() instead of dev_err() to prevent flooding the console\nand triggering an RCU stall.\n\nFixes: aca951a22a1d (\"[PATCH] input-driver-yealink-P1K-usb-phone\")\nAssisted-by: Gemini:gemini-3.8-flash syzbot\nReported-by: syzbot+78e2288f58b881ed3c45@syzkaller.appspotmail.com\nCloses: https://syzkaller.appspot.com/bug?extid=78e2288f58b881ed3c45\nLink: https://syzkaller.appspot.com/ai_job?id=89a6c0c7-a0c4-4f05-b1b1-e36a92e373e0\nTo: \"Henk Vergonet\" \u003cHenk.Vergonet@gmail.com\u003e\nTo: \"Dmitry Torokhov\" \u003cdmitry.torokhov@gmail.com\u003e\nTo: \u003clinux-input@vger.kernel.org\u003e\nCc: \u003clinux-kernel@vger.kernel.org\u003e\n\n---\nv4:\n- In urb_ctl_callback(), resubmit urb_ctl directly instead of jumping into the switch statement.\n\nv3:\n- Only abort URB submission on fatal errors (-ECONNRESET, -ENOENT, -ESHUTDOWN, -ENODEV).\n- Skip processing packet data and jump directly to resubmission on non-fatal errors.\n- Use dev_err_ratelimited() instead of dev_err() to prevent console flooding.\n- Drop is_fatal_error() helper in favor of switch statements.\nhttps://lore.kernel.org/all/2b0508e9-fe78-40dd-a290-7156817e394c@mail.kernel.org/T/\n\nv2:\n- Factored out fatal error checks into is_fatal_error() helper\nhttps://lore.kernel.org/all/2a0b5e96-dd8a-4ce9-ba3f-dd9efa26275d@mail.kernel.org/T/\n\nv1:\nhttps://lore.kernel.org/all/57cf484d-3235-473f-a61d-570585626176@mail.kernel.org/T/\n---\ndiff --git a/drivers/input/misc/yealink.c b/drivers/input/misc/yealink.c\nindex 560f895a0..f0ec4c5ea 100644\n--- a/drivers/input/misc/yealink.c\n+++ b/drivers/input/misc/yealink.c\n@@ -405,9 +405,19 @@ static void urb_irq_callback(struct urb *urb)\n \tstruct yealink_dev *yld = urb-\u003econtext;\n \tint ret, status = urb-\u003estatus;\n \n-\tif (status)\n-\t\tdev_err(\u0026yld-\u003eintf-\u003edev, \"%s - urb status %d\\n\",\n-\t\t\t__func__, status);\n+\tswitch (status) {\n+\tcase 0:\n+\t\tbreak;\n+\tcase -ECONNRESET:\n+\tcase -ENOENT:\n+\tcase -ESHUTDOWN:\n+\tcase -ENODEV:\n+\t\treturn;\n+\tdefault:\n+\t\tdev_err_ratelimited(\u0026yld-\u003eintf-\u003edev, \"%s - urb status %d\\n\",\n+\t\t\t\t    __func__, status);\n+\t\tgoto resubmit;\n+\t}\n \n \tswitch (yld-\u003eirq_data-\u003ecmd) {\n \tcase CMD_KEYPRESS:\n@@ -429,12 +439,13 @@ static void urb_irq_callback(struct urb *urb)\n \n \tyealink_do_idle_tasks(yld);\n \n+resubmit:\n \tif (!yld-\u003eshutdown) {\n \t\tret = usb_submit_urb(yld-\u003eurb_ctl, GFP_ATOMIC);\n \t\tif (ret \u0026\u0026 ret != -EPERM)\n-\t\t\tdev_err(\u0026yld-\u003eintf-\u003edev,\n-\t\t\t\t\"%s - usb_submit_urb failed %d\\n\",\n-\t\t\t\t__func__, ret);\n+\t\t\tdev_err_ratelimited(\u0026yld-\u003eintf-\u003edev,\n+\t\t\t\t\t    \"%s - usb_submit_urb failed %d\\n\",\n+\t\t\t\t\t    __func__, ret);\n \t}\n }\n \n@@ -443,9 +454,21 @@ static void urb_ctl_callback(struct urb *urb)\n \tstruct yealink_dev *yld = urb-\u003econtext;\n \tint ret = 0, status = urb-\u003estatus;\n \n-\tif (status)\n-\t\tdev_err(\u0026yld-\u003eintf-\u003edev, \"%s - urb status %d\\n\",\n-\t\t\t__func__, status);\n+\tswitch (status) {\n+\tcase 0:\n+\t\tbreak;\n+\tcase -ECONNRESET:\n+\tcase -ENOENT:\n+\tcase -ESHUTDOWN:\n+\tcase -ENODEV:\n+\t\treturn;\n+\tdefault:\n+\t\tdev_err_ratelimited(\u0026yld-\u003eintf-\u003edev, \"%s - urb status %d\\n\",\n+\t\t\t\t    __func__, status);\n+\t\tif (!yld-\u003eshutdown)\n+\t\t\tret = usb_submit_urb(yld-\u003eurb_ctl, GFP_ATOMIC);\n+\t\tgoto out;\n+\t}\n \n \tswitch (yld-\u003ectl_data-\u003ecmd) {\n \tcase CMD_KEYPRESS:\n@@ -462,9 +485,11 @@ static void urb_ctl_callback(struct urb *urb)\n \t\tbreak;\n \t}\n \n+out:\n \tif (ret \u0026\u0026 ret != -EPERM)\n-\t\tdev_err(\u0026yld-\u003eintf-\u003edev, \"%s - usb_submit_urb failed %d\\n\",\n-\t\t\t__func__, ret);\n+\t\tdev_err_ratelimited(\u0026yld-\u003eintf-\u003edev,\n+\t\t\t\t    \"%s - usb_submit_urb failed %d\\n\",\n+\t\t\t\t    __func__, ret);\n }\n \n /*******************************************************************************\n\n\nbase-commit: 1590cf0329716306e948a8fc29f1d3ee87d3989f\n-- \nThis is an AI-generated patch subject to moderation.\nReply with '#syz upstream' to Sign-off the patch as a human author\nand send it to the upstream kernel mailing lists.\nReply with '#syz reject' to reject it ('#syz unreject' to undo).\n\nSee https://goo.gle/syzbot-ai-patches for information about AI-generated patches.\nYou can comment on the patch as usual, syzbot will try to address\nthe comments and send a new version of the patch if necessary.\nsyzbot engineers can be reached at syzkaller@googlegroups.com."
}

7/2

2026/09/21 13:37

llm

finding-triage-evaluator

Model:

gemini-3.8-flash

Args:

null

Results:

null

Tokens:

							input: 10614
							output: 186
							thoughts: 975

Thoughts:

**Analysis of the Hung Task Crash After Patch Application**

Okay, let's break this down. The problem is a hung task timeout, specifically, tasks blocked for an extended period (>143 seconds). The backtraces and lock reports point directly to NFS and its daemon (nfsd). Specifically, `nfsd_mutex` is the culprit, being held by `nfsd_shutdown_threads` (triggered by `deactivate_super`), while writer threads (`write_versions`, `write_threads`) are trying to acquire it. There's a clear deadlock scenario here, and it's happening during an NFS-related operation. I see the conflicting locks are, the `nfsd_mutex` in shutdown, while writers are blocking on the same mutex.

The patch in question, however, is a modification to the `drivers/input/misc/yealink.c` file – a USB VoIP phone driver. My immediate thought is, "Wait, how could a USB input driver cause an NFS daemon locking issue?". I'm going to quickly check the crash report to ensure I haven't missed a connection, some subtle interaction.

Hmm, after a thorough review, the Yealink driver is completely absent from the crash report's stack traces, lock information, and the NMI backtraces. There is absolutely no indication of any involvement from `yealink.c` in this crash. The evidence is clear; it's a pure NFS issue. The root cause is a deadlock involving `nfsd_mutex` during shutdown and concurrent write operations.

The patch's modification is in a completely unrelated subsystem. Therefore, I can confidently conclude that the patch did not introduce this crash. It is a coincidental event. This is an NFS regression. Now, let's formulate my response and set the results accordingly.

8/2

2026/09/21 13:37

tool

set-results

Args:

{
  "Introduced": false,
  "Reasoning": "The crash report indicates a hung task warning where multiple tasks (`syz.9.8013:27368`, `syz.9.8013:27371`, `syz.4.7067:24882`) are blocked waiting to acquire `nfsd_mutex` in `fs/nfsd` (`write_versions`, `write_threads`, `nfsd_shutdown_threads`). \n\nThe tested patch series only modifies `drivers/input/misc/yealink.c` (handling USB URB completion callbacks for the Yealink USB phone driver). It does not touch NFS, NFSD, VFS, or any related locking or subsystems. The reported hang is completely unrelated to the patch."
}

Results:

{
  "Introduced": false,
  "Reasoning": "The crash report indicates a hung task warning where multiple tasks (`syz.9.8013:27368`, `syz.9.8013:27371`, `syz.4.7067:24882`) are blocked waiting to acquire `nfsd_mutex` in `fs/nfsd` (`write_versions`, `write_threads`, `nfsd_shutdown_threads`). \n\nThe tested patch series only modifies `drivers/input/misc/yealink.c` (handling USB URB completion callbacks for the Yealink USB phone driver). It does not touch NFS, NFSD, VFS, or any related locking or subsystems. The reported hang is completely unrelated to the patch."
}

LLM Calls Summary:
Total Calls	Total Tokens	Avg Tokens	Total Duration (Seconds)	Avg Duration (Seconds)

Tool Calls Summary:
Total Calls	Total Duration (Seconds)	Avg Duration (Seconds)