CVE-2021-46976 in Linux
Zusammenfassung
von VulDB • 02.07.2026
Based on the kernel log snippet provided, here is an analysis of what happened and how to proceed.
### **1. Summary** * **Event:** A **Kernel Oops/Panic** occurred in the Linux kernel. * **Cause:** Likely a **NULL pointer dereference** or invalid memory access (indicated by `CR2` value). * **Context:** The crash happened while executing work queued on a **kernel worker thread**. * **Triggering Function:** The call trace points to `__active_retire`, which is part of the kernel's **workqueue subsystem** (`process_one_work`).
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### **2. Key Log Analysis**
#### **A. CPU Registers (Crash Context)** ```text CR0: 0000000080050033 CR2: 0000239514955000 <-- Critical! This is the faulting address. CR3: 00000007f82da001 <-- Page table base register (process context). CR4: 0000000000760ee0 PKRU: 55555554 <-- Protection Keys for Userspace. ``` * **`CR2 = 0x239514955000`**: This is the virtual address that caused the page fault. It looks like a high kernel-space address, possibly an unmapped or corrupted pointer. If this value were `0`, it would be a classic NULL dereference. Since it’s non-zero but likely invalid in context, it suggests **use-after-free**, **dangling pointer**, or **corrupted data structure**.
#### **B. Call Trace** ```text Call Trace: __active_retire+0x77/0xcf <-- The function where the crash occurred. process_one_work+0x1da/0x394 <-- Workqueue worker processing a task. worker_thread+0x216/0x375 <-- Kernel thread executing workqueues. kthread+0x147/0x156 <-- Generic kernel thread entry point. ret_from_fork+0x1f/0x40 <-- Return from fork (kernel thread creation). ``` * **`__active_retire`**: This function is part of the Linux workqueue implementation (`kernel/workqueue.c`). It handles retiring active workers or managing worker pools. The crash here suggests a corruption in the workqueue data structures or an invalid pointer passed to it during cleanup/retirement.
#### **C. Modules Loaded** The list includes many drivers, notably: * `snd_sof_*` (Sound Open Firmware - Intel audio) * `intel_ipu6_*`, `ov2740`, `ov8856` (Intel IPU6 camera subsystem) * `cros_ec_*` (ChromeOS Embedded Controller drivers) * `soundwire_*`
This suggests the system is likely a **modern laptop/desktop with Intel hardware**, possibly running Chrome OS or a distro with similar driver stacks. The crash may be indirectly related to audio, camera, or power management subsystems if they triggered workqueue tasks that corrupted memory.
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### **3. Likely Causes** 1. **Kernel Bug in Workqueue Subsystem**: A race condition or bug in `__active_retire` due to concurrent modifications of worker structures. 2. **Driver-Induced Corruption**: One of the loaded modules (e.g., audio, camera, or ChromeOS EC driver) may have freed memory that was still referenced by a workqueue item, leading to use-after-free when `__active_retire` accessed it. 3. **Memory Corruption**: General heap corruption from another part of the system affecting kernel data structures.
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### **4. Recommended Actions**
#### **Step 1: Gather More Information** * **Full Oops Log**: The snippet is truncated. Look for lines before `Call Trace` that show: * Which process/task was running (`task:` line). * Any preceding warnings or errors from specific drivers (e.g., `[drm]`, `[snd_soc_sof]`).
* **Kernel Version**: Run `uname -r`. This crash may be fixed in newer kernels.
#### **Step 2: Check for Known Issues** * Search the Linux kernel bugzilla (`bugzilla.kernel.org`) or your distro’s issue tracker with keywords: * `"__active_retire" CR2` * `"process_one_work" crash workqueue` * Combine with
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