CVE-2026-68437 in Linux
Сводка
по VulDB • 12.08.2026
Based on the kernel log snippet provided, here is an analysis of the crash:
### **Summary** This is a **kernel panic/oops in the PowerVR GPU driver (`powervr`)** during command buffer submission. The crash occurs inside `pvr_cccb_write_command_with_header`, likely due to an invalid memory access or corrupted data structure when writing commands to the Command Control Buffer (CCCB).
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### **Key Observations**
#### 1. **Crash Location** ```text Call trace: pvr_cccb_write_command_with_header+0x2c4/0x330 [powervr] (P)
pvr_queue_submit_job_to_cccb+0x57c/0xa74 [powervr]
pvr_queue_run_job+0x3a4/0x990 [powervr]
drm_sched_run_job_work+0x580/0xd48 [gpu_sched]
``` - The crash happens in the **PowerVR DRM driver** (`[powervr]`).
- Specifically, during `pvr_cccb_write_command_with_header`, which writes GPU commands into a shared memory buffer (CCCB). - This is part of the job submission pipeline: `drm_sched` → PowerVR scheduler → CCCB write.
#### 2. **Register State Analysis** The register dump shows several suspicious values that may hint at the root cause:
| Register | Value | Possible Meaning | |----------|----------------|----------------------------------------------------------------------------------| | **x0** | `0x2f` | Likely an error code or small integer argument (e.g., command type, offset). | | **x1** | `0xfff` | Could be a size/length parameter. | | **x8–x9**| `0xf2f2f2...`, `0xf3f3f3...` | These are classic **"poison" values**. In Linux kernel debugging, `0xF2F2F2F2` and `0xF3F3F3F3` are often used by KASAN (Kernel Address Sanitizer) or other debuggers to mark **freed memory** (`UAF`) or **uninitialized memory**. | | **x17–x16**| `0x20020000`, `0x20000` | May be related to command headers or flags. | | **x25/x24** | Kernel addresses (`ffff8...`) | Likely pointers to structures (e.g., job, CCCB buffer). |
> ???? **Critical Clue**: The presence of `0xF3F3F3F3` and `0xF2F2F2F2` strongly suggests that the driver is accessing **freed or corrupted memory**. This could be due to: > - A use-after-free (UAF) bug. > - Memory corruption in the CCCB buffer. > - Race condition between job submission and cleanup.
#### 3. **Architecture** - The register names (`x0`–`x29`) indicate an **ARM64/aarch64** system. - PowerVR GPUs are common in embedded/mobile SoCs (e.g., NXP i.MX, Rockchip, Allwinner).
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### **Likely Root Causes**
1. **Use-After-Free or Double Free**: - The job structure (`pvr_queue_run_job`) may have been freed while still being processed. - The CCCB buffer pointer might be stale.
2. **Memory Corruption in CCCB**: - If the user-space application wrote invalid data into the command stream, it could corrupt kernel structures during parsing/writing.
3. **Race Condition**: - Multiple threads/processes submitting jobs simultaneously without proper locking. - GPU reset or error recovery path interfering with active job submission.
4. **Driver Bug in `pvr_cccb_write_command_with_header`**: - Off-by-one errors, incorrect bounds checking, or null pointer dereference when writing headers/commands.
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### **Recommended Debugging Steps**
#### ✅ 1. **Enable KASAN (Kernel Address Sanitizer)** If not already enabled, recompile the kernel with `CONFIG_KASAN=y` to get precise details on memory corruption: ```bash # Check if KASAN is active dmesg | grep -i kasan ``` KASAN will provide a detailed stack trace showing exactly which freed object was accessed.
#### ✅ 2. **Check for User-Space Issues** - Ensure the user-space GPU driver (e.g., `libpvr`, Mesa, or proprietary SDK) is compatible with the
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