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 shows a KASAN vmalloc-out-of-bounds write in `sys_fillrect` triggered during virtual console scroll/clear operations (`ksys_write` -\u003e `con_write` -\u003e `do_con_write` -\u003e `csi_ECMA` -\u003e `con_scroll` -\u003e `fbcon_scroll` -\u003e `__fbcon_clear` -\u003e `bit_clear` -\u003e `drm_fbdev_shmem_defio_fillrect` -\u003e `sys_fillrect`).\n\nThe patch under test modifies only `drivers/input/misc/yealink.c`, fixing URB submission handling and rate-limiting error logging in the Yealink USB VoIP phone input driver. The patch does not touch `sys_fillrect`, DRM, fbcon, TTY, or any related data structures or subsystems. The crash is an unrelated issue in the fbcon/DRM subsystem triggered during fuzzing." }
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 shows a KASAN vmalloc-out-of-bounds write in `sys_fillrect` triggered during virtual console scroll/clear operations (`ksys_write` -\u003e `con_write` -\u003e `do_con_write` -\u003e `csi_ECMA` -\u003e `con_scroll` -\u003e `fbcon_scroll` -\u003e `__fbcon_clear` -\u003e `bit_clear` -\u003e `drm_fbdev_shmem_defio_fillrect` -\u003e `sys_fillrect`).\n\nThe patch under test modifies only `drivers/input/misc/yealink.c`, fixing URB submission handling and rate-limiting error logging in the Yealink USB VoIP phone input driver. The patch does not touch `sys_fillrect`, DRM, fbcon, TTY, or any related data structures or subsystems. The crash is an unrelated issue in the fbcon/DRM subsystem triggered during fuzzing." } 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: ================================================================== BUG: KASAN: vmalloc-out-of-bounds in sys_fillrect+0x1da5/0x2570 Write of size 8 at addr ffffc90004e1d000 by task syz.0.2366/17584 CPU: 0 UID: 0 PID: 17584 Comm: syz.0.2366 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 print_address_description+0x55/0x1e0 print_report+0x58/0x70 kasan_report+0x117/0x150 sys_fillrect+0x1da5/0x2570 drm_fbdev_shmem_defio_fillrect+0x2c/0x110 bit_clear+0x168/0x200 __fbcon_clear+0x9cd/0xd30 fbcon_scroll+0x47e/0x7c0 con_scroll+0x783/0xa10 csi_ECMA+0x486/0x6850 do_con_write+0x41ac/0x5500 con_write+0x27/0x290 n_tty_write+0xd49/0x11e0 file_tty_write+0x509/0x9c0 vfs_write+0x612/0xba0 ksys_write+0x150/0x270 do_syscall_64+0x174/0x580 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7fc04399e159 Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007fc04478d028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 RAX: ffffffffffffffda RBX: 00007fc043c25fa0 RCX: 00007fc04399e159 RDX: 0000000000001006 RSI: 0000200000001580 RDI: 0000000000000004 RBP: 00007fc043a3506b R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007fc043c26038 R14: 00007fc043c25fa0 R15: 00007ffea095f878 </TASK> The buggy address belongs to a vmalloc virtual mapping Memory state around the buggy address: ffffc90004e1cf00: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 ffffc90004e1cf80: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 >ffffc90004e1d000: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 ^ ffffc90004e1d080: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 ffffc90004e1d100: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 ================================================================== 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: 3796 output: 20 thoughts: 198 Thoughts: Analyzing a Suspected yealink Driver Issue Okay, let's dive into this. First, I need to look at the patch and the associated crash report. Alright, the patch appears to be touching `drivers/input/misc/yealink.c`, which immediately piques my interest. Input drivers can be tricky, especially with vendor-specific hardware like Yealink phones. The crash report itself shows a KASAN `vmalloc-out-of-bounds` error, specifically within `sys_fillrect`. That's a red flag – memory corruption during a rectangular fill operation is never good. The call trace is interesting; it goes from `sys_fillrect` down through `drm_fbdev_shmem_defio_fillrect`, then down to `fbcon` and eventually `n_tty_write`. That path suggests a problem might be related to framebuffer interaction, console, and potentially terminal interaction. This could be a race condition, a buffer overflow, or an uninitialized memory issue. Now, I'll switch gears and pull up the entire patch series and run `git show HEAD` to get the context surrounding this particular commit. Understanding the larger changes around `yealink.c` might reveal the root cause or clues. Hopefully, the changes will shed light on what the intent was, and if it could have introduced this issue, or whether it exposed a pre-existing flaw. This will inform my assessment of the bug's severity and potential impact. I need to understand where things went sideways in the driver.
4/2	2026/09/21 13:37	tool	series-patches	0m Error: missing argument "PatchNum" Args: null Results: { "error": "missing argument \"PatchNum\"" }
5/2	2026/09/21 13:37	tool	git-show	0m Args: null 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\ndiff --git a/drivers/input/misc/yealink.c b/drivers/input/misc/yealink.c\nindex 560f895a00cda..f0ec4c5ea94c2 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" }
6/2	2026/09/21 13:37	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 5397 output: 15 thoughts: 16 Thoughts: Okay, let's break this down. Here's how I'd approach this, considering I'm probably dealing with some code or data structure given the "patches" and "series" terminology: My Analytical Process Alright, the first thing I'm seeing is a reference to "series-patches" and a specific PatchNum of 1. My initial thought process is starting to construct a mental model of what this data likely represents. We're probably looking at a system that organizes some kind of code or data changes. The term "series" suggests an ordered sequence, a progression of modifications, or versions. And "patches" very strongly implies we are in a version control context like git or a similar patch management system. This system is very likely applying an update to something. Since PatchNum is 1, this implies the first patch in the series is being considered. I'm already anticipating some of the common things I'll be looking for in such a context; are there dependencies, conflicts, or any information about the nature of this patch, its intended purpose, or its intended effect? Does this reference to PatchNum=1 imply there might be other patches later in this series? Depending on how the system is structured, PatchNum = 1 could mean multiple things. 1) It could be the very first patch in a brand new series. 2) It could mean this series of patches has been applied before, and it is simply being re-applied/re-evaluated. I need more information to discern the actual context of this piece of information.
7/2	2026/09/21 13:38	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." }
8/2	2026/09/21 13:38	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 8020 output: 18 thoughts: 184 Thoughts: Analyzing the Crash: A Deep Dive Okay, let's dissect this. We have a crash, a KASAN vmalloc-out-of-bounds error specifically triggered within `sys_fillrect`. The kernel is reporting a write of size 8 at a specific virtual address by a syz.0.2366/17584 task. Right away, this screams memory corruption. We need to understand how `sys_fillrect` is being invoked and, crucially, the path leading to this out-of-bounds write. The call trace is our roadmap: `sys_fillrect` -> `drm_fbdev_shmem_defio_fillrect` -> `bit_clear` -> `__fbcon_clear` -> `fbcon_scroll` -> `con_scroll` -> `csi_ECMA` -> `do_con_write` -> `con_write` -> `n_tty_write` -> `file_tty_write` -> `vfs_write` -> `ksys_write`. That tells us this is related to frame buffer operations, console handling, and ultimately, a write syscall. Time to start digging into the `sys_fillrect` implementation. I need to pinpoint the exact location of the out-of-bounds write within the function. Looking at the code around `sys_fillrect+0x1da5` should illuminate the cause.
9/2	2026/09/21 13:38	tool	grepper	0m Args: { "Expression": "sys_fillrect" } Results: { "Output": "drivers/video/fbdev/core/Kconfig=61=config FB_SYS_FILLRECT\n--\ndrivers/video/fbdev/core/Kconfig-64-\thelp\ndrivers/video/fbdev/core/Kconfig:65:\t Include the sys_fillrect function for generic software rectangle\ndrivers/video/fbdev/core/Kconfig-66-\t filling. This is used by drivers that don't provide their own\n--\ndrivers/video/fbdev/core/sysfillrect.c-18-\ndrivers/video/fbdev/core/sysfillrect.c:19:void sys_fillrect(struct fb_info p, const struct fb_fillrect rect)\ndrivers/video/fbdev/core/sysfillrect.c-20-{\n--\ndrivers/video/fbdev/core/sysfillrect.c-25-}\ndrivers/video/fbdev/core/sysfillrect.c:26:EXPORT_SYMBOL(sys_fillrect);\ndrivers/video/fbdev/core/sysfillrect.c-27-\n--\ndrivers/video/fbdev/sh_mobile_lcdcfb.c=1655=static void sh_mobile_lcdc_fillrect(struct fb_info info,\n--\ndrivers/video/fbdev/sh_mobile_lcdcfb.c-1657-{\ndrivers/video/fbdev/sh_mobile_lcdcfb.c:1658:\tsys_fillrect(info, rect);\ndrivers/video/fbdev/sh_mobile_lcdcfb.c-1659-\tsh_mobile_lcdc_deferred_io_touch(info);\n--\ndrivers/video/fbdev/wmt_ge_rops.h=17=static inline void wmt_ge_fillrect(struct fb_info p,\n--\ndrivers/video/fbdev/wmt_ge_rops.h-19-{\ndrivers/video/fbdev/wmt_ge_rops.h:20:\tsys_fillrect(p, rect);\ndrivers/video/fbdev/wmt_ge_rops.h-21-}\n--\ninclude/linux/fb.h=549=int fb_io_mmap(struct fb_info info, struct vm_area_struct vma);\n--\ninclude/linux/fb.h-571-\ninclude/linux/fb.h:572:extern void sys_fillrect(struct fb_info info, const struct fb_fillrect rect);\ninclude/linux/fb.h-573-extern void sys_copyarea(struct fb_info info, const struct fb_copyarea area);\n--\ninclude/linux/fb.h=577=extern ssize_t fb_sys_write(struct fb_info info, const char __user buf,\n--\ninclude/linux/fb.h-584-#define __FB_DEFAULT_SYSMEM_OPS_DRAW \\\ninclude/linux/fb.h:585:\t.fb_fillrect\t= sys_fillrect, \\\ninclude/linux/fb.h-586-\t.fb_copyarea\t= sys_copyarea, \\\n--\ninclude/linux/fb.h-597-#define __FB_DEFAULT_DMAMEM_OPS_DRAW \\\ninclude/linux/fb.h:598:\t.fb_fillrect\t= sys_fillrect, \\\ninclude/linux/fb.h-599-\t.fb_copyarea\t= sys_copyarea, \\\n" }
10/2	2026/09/21 13:38	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 9376 output: 37 thoughts: 199 Thoughts: My Initial Assessment of the Crash Okay, let's break this down. The patch I'm examining is isolated to `drivers/input/misc/yealink.c`, which is the USB VoIP phone input driver. The crash, however, is happening deep down in the graphics stack, specifically within `sys_fillrect`. That's being called from `drm_fbdev_shmem_defio_fillrect` and then propagates through a chain that involves `bit_clear`, `__fbcon_clear`, `fbcon_scroll`, and so on, ultimately leading to a `vfs_write` call through the tty/virtual console path. So, this is a write to a tty/virtual console (fbcon), got it. Now, the real question: does `yealink.c` have any plausible connection to this part of the system? We're talking about DRM, fbdev, fbcon, tty, and console drawing. It seems highly unlikely, based on the description, that a VoIP phone input driver would be directly involved in rendering operations. This seems like a completely unrelated area of the kernel. I need to take a closer look at `drivers/input/misc/yealink.c` itself. There is possibly some subtle interface that is being triggered that is resulting in this crash, but it requires a deeper dive into the code.
11/2	2026/09/21 13:38	tool	grepper	0m Error: no matches Args: { "Expression": "fb\|drm\|console\|tty", "PathPrefix": "drivers/input/misc/yealink.c" } Results: { "error": "no matches" }
12/2	2026/09/21 13:38	llm	finding-triage-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 9919 output: 217 thoughts: 1057 Thoughts: Analysis of the Bug Report and Patch Relevance Okay, so I've got this crash report: `BUG: KASAN: vmalloc-out-of-bounds in sys_fillrect`. My initial thought is that it's an fbcon/drm_fbdev_shmem issue. The stack trace clearly points to virtual console operations: we've got `sys_fillrect` called from `drm_fbdev_shmem_defio_fillrect`, which is being called by `fbcon_scroll`, `__fbcon_clear`, and further up the call stack, right through `csi_ECMA` which handles escape sequences. This is a known issue. Now, my task is to determine if the patch I've been testing, "[PATCH RFC v4] Input: yealink - abort URB submission on fatal errors", has anything to do with it. My instinct says no, but I need to be thorough. I've re-examined the code in `drivers/input/misc/yealink.c`—the file modified by the patch. I've also checked the diff again, confirming that the patch only modifies URB completion handling within the `yealink.c` module, focusing on error checking of the USB transfers. There is absolutely no connection between the patch and the DRM, fbcon, sys_fillrect, or TTY subsystems. I've carefully considered these aspects: * Patch Content: The patch strictly handles USB URB callbacks for a yealink USB VoIP phone and nothing else. * Crash Context: The crash is happening in the fbcon layer, within a virtual console operation. * Call Stack: It traces through `sys_fillrect` and related functions, all connected to screen clearing and scrolling. * File Overlap: There are no shared files in the backtrace. * Global State Impact: The patch doesn't touch any global state, memory allocators, fbcon structures, or anything used by DRM/fbcon. Therefore, the patch I tested didn't introduce the bug. It's an unrelated fbcon/drm_fbdev_shmem issue. It's an existing bug that the patch didn't affect, or introduce in any way. I can say, with confidence, that the patch did not cause this issue.
13/2	2026/09/21 13:38	tool	set-results	0m Args: { "Introduced": false, "Reasoning": "The crash report shows a KASAN vmalloc-out-of-bounds write in `sys_fillrect` triggered during virtual console scroll/clear operations (`ksys_write` -\u003e `con_write` -\u003e `do_con_write` -\u003e `csi_ECMA` -\u003e `con_scroll` -\u003e `fbcon_scroll` -\u003e `__fbcon_clear` -\u003e `bit_clear` -\u003e `drm_fbdev_shmem_defio_fillrect` -\u003e `sys_fillrect`).\n\nThe patch under test modifies only `drivers/input/misc/yealink.c`, fixing URB submission handling and rate-limiting error logging in the Yealink USB VoIP phone input driver. The patch does not touch `sys_fillrect`, DRM, fbcon, TTY, or any related data structures or subsystems. The crash is an unrelated issue in the fbcon/DRM subsystem triggered during fuzzing." } Results: { "Introduced": false, "Reasoning": "The crash report shows a KASAN vmalloc-out-of-bounds write in `sys_fillrect` triggered during virtual console scroll/clear operations (`ksys_write` -\u003e `con_write` -\u003e `do_con_write` -\u003e `csi_ECMA` -\u003e `con_scroll` -\u003e `fbcon_scroll` -\u003e `__fbcon_clear` -\u003e `bit_clear` -\u003e `drm_fbdev_shmem_defio_fillrect` -\u003e `sys_fillrect`).\n\nThe patch under test modifies only `drivers/input/misc/yealink.c`, fixing URB submission handling and rate-limiting error logging in the Yealink USB VoIP phone input driver. The patch does not touch `sys_fillrect`, DRM, fbcon, TTY, or any related data structures or subsystems. The crash is an unrelated issue in the fbcon/DRM subsystem triggered during fuzzing." }

{
  "Introduced": false,
  "Reasoning": "The crash report shows a KASAN vmalloc-out-of-bounds write in `sys_fillrect` triggered during virtual console scroll/clear operations (`ksys_write` -\u003e `con_write` -\u003e `do_con_write` -\u003e `csi_ECMA` -\u003e `con_scroll` -\u003e `fbcon_scroll` -\u003e `__fbcon_clear` -\u003e `bit_clear` -\u003e `drm_fbdev_shmem_defio_fillrect` -\u003e `sys_fillrect`).\n\nThe patch under test modifies only `drivers/input/misc/yealink.c`, fixing URB submission handling and rate-limiting error logging in the Yealink USB VoIP phone input driver. The patch does not touch `sys_fillrect`, DRM, fbcon, TTY, or any related data structures or subsystems. The crash is an unrelated issue in the fbcon/DRM subsystem triggered during fuzzing."
}

{
  "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"
}

{
  "Introduced": false,
  "Reasoning": "The crash report shows a KASAN vmalloc-out-of-bounds write in `sys_fillrect` triggered during virtual console scroll/clear operations (`ksys_write` -\u003e `con_write` -\u003e `do_con_write` -\u003e `csi_ECMA` -\u003e `con_scroll` -\u003e `fbcon_scroll` -\u003e `__fbcon_clear` -\u003e `bit_clear` -\u003e `drm_fbdev_shmem_defio_fillrect` -\u003e `sys_fillrect`).\n\nThe patch under test modifies only `drivers/input/misc/yealink.c`, fixing URB submission handling and rate-limiting error logging in the Yealink USB VoIP phone input driver. The patch does not touch `sys_fillrect`, DRM, fbcon, TTY, or any related data structures or subsystems. The crash is an unrelated issue in the fbcon/DRM subsystem triggered during fuzzing."
}

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.

Target architecture: amd64

The kernel crash report to triage is:

==================================================================
BUG: KASAN: vmalloc-out-of-bounds in sys_fillrect+0x1da5/0x2570
Write of size 8 at addr ffffc90004e1d000 by task syz.0.2366/17584

CPU: 0 UID: 0 PID: 17584 Comm: syz.0.2366 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
 print_address_description+0x55/0x1e0
 print_report+0x58/0x70
 kasan_report+0x117/0x150
 sys_fillrect+0x1da5/0x2570
 drm_fbdev_shmem_defio_fillrect+0x2c/0x110
 bit_clear+0x168/0x200
 __fbcon_clear+0x9cd/0xd30
 fbcon_scroll+0x47e/0x7c0
 con_scroll+0x783/0xa10
 csi_ECMA+0x486/0x6850
 do_con_write+0x41ac/0x5500
 con_write+0x27/0x290
 n_tty_write+0xd49/0x11e0
 file_tty_write+0x509/0x9c0
 vfs_write+0x612/0xba0
 ksys_write+0x150/0x270
 do_syscall_64+0x174/0x580
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fc04399e159
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fc04478d028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007fc043c25fa0 RCX: 00007fc04399e159
RDX: 0000000000001006 RSI: 0000200000001580 RDI: 0000000000000004
RBP: 00007fc043a3506b R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fc043c26038 R14: 00007fc043c25fa0 R15: 00007ffea095f878
 </TASK>

The buggy address belongs to a vmalloc virtual mapping
Memory state around the buggy address:
 ffffc90004e1cf00: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
 ffffc90004e1cf80: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
>ffffc90004e1d000: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
                   ^
 ffffc90004e1d080: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
 ffffc90004e1d100: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
==================================================================



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

							input: 3796
							output: 20
							thoughts: 198

**Analyzing a Suspected yealink Driver Issue**

Okay, let's dive into this. First, I need to look at the patch and the associated crash report. Alright, the patch appears to be touching `drivers/input/misc/yealink.c`, which immediately piques my interest. Input drivers can be tricky, especially with vendor-specific hardware like Yealink phones. The crash report itself shows a KASAN `vmalloc-out-of-bounds` error, specifically within `sys_fillrect`. That's a red flag – memory corruption during a rectangular fill operation is never good. The call trace is interesting; it goes from `sys_fillrect` down through `drm_fbdev_shmem_defio_fillrect`, then down to `fbcon` and eventually `n_tty_write`. That path suggests a problem might be related to framebuffer interaction, console, and potentially terminal interaction. This could be a race condition, a buffer overflow, or an uninitialized memory issue.

Now, I'll switch gears and pull up the entire patch series and run `git show HEAD` to get the context surrounding this particular commit. Understanding the larger changes around `yealink.c` might reveal the root cause or clues. Hopefully, the changes will shed light on what the intent was, and if it could have introduced this issue, or whether it exposed a pre-existing flaw. This will inform my assessment of the bug's severity and potential impact. I need to understand where things went sideways in the driver.

missing argument "PatchNum"

{
  "error": "missing argument \"PatchNum\""
}

{
  "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\ndiff --git a/drivers/input/misc/yealink.c b/drivers/input/misc/yealink.c\nindex 560f895a00cda..f0ec4c5ea94c2 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"
}

							input: 5397
							output: 15
							thoughts: 16

Okay, let's break this down. Here's how I'd approach this, considering I'm probably dealing with some code or data structure given the "patches" and "series" terminology:

**My Analytical Process**

Alright, the first thing I'm seeing is a reference to "series-patches" and a specific PatchNum of 1. My initial thought process is starting to construct a mental model of what this data likely represents. We're probably looking at a system that organizes some kind of code or data changes. The term "series" suggests an ordered sequence, a progression of modifications, or versions. And "patches" very strongly implies we are in a version control context like git or a similar patch management system. This system is very likely applying an update to something. Since PatchNum is 1, this implies the first patch in the series is being considered. I'm already anticipating some of the common things I'll be looking for in such a context; are there dependencies, conflicts, or any information about the nature of this patch, its intended purpose, or its intended effect? Does this reference to PatchNum=1 imply there might be other patches later in this series? Depending on how the system is structured, PatchNum = 1 could mean multiple things. 1) It could be the very first patch in a brand new series. 2) It could mean this series of patches has been applied before, and it is simply being re-applied/re-evaluated. I need more information to discern the actual context of this piece of information.

{
  "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."
}

							input: 8020
							output: 18
							thoughts: 184

**Analyzing the Crash: A Deep Dive**

Okay, let's dissect this. We have a crash, a KASAN vmalloc-out-of-bounds error specifically triggered within `sys_fillrect`. The kernel is reporting a write of size 8 at a specific virtual address by a syz.0.2366/17584 task.  Right away, this screams memory corruption. We need to understand how `sys_fillrect` is being invoked and, crucially, the path leading to this out-of-bounds write.  The call trace is our roadmap: `sys_fillrect` -> `drm_fbdev_shmem_defio_fillrect` -> `bit_clear` -> `__fbcon_clear` -> `fbcon_scroll` -> `con_scroll` -> `csi_ECMA` -> `do_con_write` -> `con_write` -> `n_tty_write` -> `file_tty_write` -> `vfs_write` -> `ksys_write`. That tells us this is related to frame buffer operations, console handling, and ultimately, a write syscall. Time to start digging into the `sys_fillrect` implementation. I need to pinpoint the exact location of the out-of-bounds write within the function. Looking at the code around `sys_fillrect+0x1da5` should illuminate the cause.

{
  "Expression": "sys_fillrect"
}

{
  "Output": "drivers/video/fbdev/core/Kconfig=61=config FB_SYS_FILLRECT\n--\ndrivers/video/fbdev/core/Kconfig-64-\thelp\ndrivers/video/fbdev/core/Kconfig:65:\t  Include the sys_fillrect function for generic software rectangle\ndrivers/video/fbdev/core/Kconfig-66-\t  filling. This is used by drivers that don't provide their own\n--\ndrivers/video/fbdev/core/sysfillrect.c-18-\ndrivers/video/fbdev/core/sysfillrect.c:19:void sys_fillrect(struct fb_info *p, const struct fb_fillrect *rect)\ndrivers/video/fbdev/core/sysfillrect.c-20-{\n--\ndrivers/video/fbdev/core/sysfillrect.c-25-}\ndrivers/video/fbdev/core/sysfillrect.c:26:EXPORT_SYMBOL(sys_fillrect);\ndrivers/video/fbdev/core/sysfillrect.c-27-\n--\ndrivers/video/fbdev/sh_mobile_lcdcfb.c=1655=static void sh_mobile_lcdc_fillrect(struct fb_info *info,\n--\ndrivers/video/fbdev/sh_mobile_lcdcfb.c-1657-{\ndrivers/video/fbdev/sh_mobile_lcdcfb.c:1658:\tsys_fillrect(info, rect);\ndrivers/video/fbdev/sh_mobile_lcdcfb.c-1659-\tsh_mobile_lcdc_deferred_io_touch(info);\n--\ndrivers/video/fbdev/wmt_ge_rops.h=17=static inline void wmt_ge_fillrect(struct fb_info *p,\n--\ndrivers/video/fbdev/wmt_ge_rops.h-19-{\ndrivers/video/fbdev/wmt_ge_rops.h:20:\tsys_fillrect(p, rect);\ndrivers/video/fbdev/wmt_ge_rops.h-21-}\n--\ninclude/linux/fb.h=549=int fb_io_mmap(struct fb_info *info, struct vm_area_struct *vma);\n--\ninclude/linux/fb.h-571-\ninclude/linux/fb.h:572:extern void sys_fillrect(struct fb_info *info, const struct fb_fillrect *rect);\ninclude/linux/fb.h-573-extern void sys_copyarea(struct fb_info *info, const struct fb_copyarea *area);\n--\ninclude/linux/fb.h=577=extern ssize_t fb_sys_write(struct fb_info *info, const char __user *buf,\n--\ninclude/linux/fb.h-584-#define __FB_DEFAULT_SYSMEM_OPS_DRAW \\\ninclude/linux/fb.h:585:\t.fb_fillrect\t= sys_fillrect, \\\ninclude/linux/fb.h-586-\t.fb_copyarea\t= sys_copyarea, \\\n--\ninclude/linux/fb.h-597-#define __FB_DEFAULT_DMAMEM_OPS_DRAW \\\ninclude/linux/fb.h:598:\t.fb_fillrect\t= sys_fillrect, \\\ninclude/linux/fb.h-599-\t.fb_copyarea\t= sys_copyarea, \\\n"
}

							input: 9376
							output: 37
							thoughts: 199

**My Initial Assessment of the Crash**

Okay, let's break this down. The patch I'm examining is isolated to `drivers/input/misc/yealink.c`, which is the USB VoIP phone input driver. The crash, however, is happening deep down in the graphics stack, specifically within `sys_fillrect`. That's being called from `drm_fbdev_shmem_defio_fillrect` and then propagates through a chain that involves `bit_clear`, `__fbcon_clear`, `fbcon_scroll`, and so on, ultimately leading to a `vfs_write` call through the tty/virtual console path. So, this is a write to a tty/virtual console (fbcon), got it.

Now, the real question: does `yealink.c` have *any* plausible connection to this part of the system? We're talking about DRM, fbdev, fbcon, tty, and console drawing. It seems highly unlikely, based on the description, that a VoIP phone input driver would be directly involved in rendering operations. This seems like a completely unrelated area of the kernel. I need to take a closer look at `drivers/input/misc/yealink.c` itself. There is possibly some subtle interface that is being triggered that is resulting in this crash, but it requires a deeper dive into the code.

{
  "Expression": "fb|drm|console|tty",
  "PathPrefix": "drivers/input/misc/yealink.c"
}

{
  "error": "no matches"
}

							input: 9919
							output: 217
							thoughts: 1057

**Analysis of the Bug Report and Patch Relevance**

Okay, so I've got this crash report: `BUG: KASAN: vmalloc-out-of-bounds in sys_fillrect`. My initial thought is that it's an fbcon/drm_fbdev_shmem issue. The stack trace clearly points to virtual console operations: we've got `sys_fillrect` called from `drm_fbdev_shmem_defio_fillrect`, which is being called by `fbcon_scroll`, `__fbcon_clear`, and further up the call stack, right through `csi_ECMA` which handles escape sequences. This is a known issue.

Now, my task is to determine if the patch I've been testing, "[PATCH RFC v4] Input: yealink - abort URB submission on fatal errors", has anything to do with it. My instinct says no, but I need to be thorough. I've re-examined the code in `drivers/input/misc/yealink.c`—the file modified by the patch. I've also checked the diff again, confirming that the patch *only* modifies URB completion handling within the `yealink.c` module, focusing on error checking of the USB transfers. There is absolutely no connection between the patch and the DRM, fbcon, sys_fillrect, or TTY subsystems.

I've carefully considered these aspects:

* **Patch Content:** The patch strictly handles USB URB callbacks for a yealink USB VoIP phone and nothing else.
* **Crash Context:** The crash is happening in the fbcon layer, within a virtual console operation.
* **Call Stack:** It traces through `sys_fillrect` and related functions, all connected to screen clearing and scrolling.
* **File Overlap:** There are no shared files in the backtrace.
* **Global State Impact:** The patch doesn't touch any global state, memory allocators, fbcon structures, or anything used by DRM/fbcon.

Therefore, the patch I tested didn't introduce the bug. It's an unrelated fbcon/drm_fbdev_shmem issue. It's an existing bug that the patch didn't affect, or introduce in any way. I can say, with confidence, that the patch did not cause this issue.

{
  "Introduced": false,
  "Reasoning": "The crash report shows a KASAN vmalloc-out-of-bounds write in `sys_fillrect` triggered during virtual console scroll/clear operations (`ksys_write` -\u003e `con_write` -\u003e `do_con_write` -\u003e `csi_ECMA` -\u003e `con_scroll` -\u003e `fbcon_scroll` -\u003e `__fbcon_clear` -\u003e `bit_clear` -\u003e `drm_fbdev_shmem_defio_fillrect` -\u003e `sys_fillrect`).\n\nThe patch under test modifies only `drivers/input/misc/yealink.c`, fixing URB submission handling and rate-limiting error logging in the Yealink USB VoIP phone input driver. The patch does not touch `sys_fillrect`, DRM, fbcon, TTY, or any related data structures or subsystems. The crash is an unrelated issue in the fbcon/DRM subsystem triggered during fuzzing."
}

{
  "Introduced": false,
  "Reasoning": "The crash report shows a KASAN vmalloc-out-of-bounds write in `sys_fillrect` triggered during virtual console scroll/clear operations (`ksys_write` -\u003e `con_write` -\u003e `do_con_write` -\u003e `csi_ECMA` -\u003e `con_scroll` -\u003e `fbcon_scroll` -\u003e `__fbcon_clear` -\u003e `bit_clear` -\u003e `drm_fbdev_shmem_defio_fillrect` -\u003e `sys_fillrect`).\n\nThe patch under test modifies only `drivers/input/misc/yealink.c`, fixing URB submission handling and rate-limiting error logging in the Yealink USB VoIP phone input driver. The patch does not touch `sys_fillrect`, DRM, fbcon, TTY, or any related data structures or subsystems. The crash is an unrelated issue in the fbcon/DRM subsystem triggered during fuzzing."
}

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)