CVE-2026-43338 in Linux
요약
\~에 의해 VulDB • 2026. 05. 19.
Based on the kernel oops trace provided, here is an analysis of the crash.
### **Summary** The system crashed with a **NULL Pointer Dereference** (`RIP: 0000000000000000`) while unmounting a **Btrfs** filesystem. The crash occurred in `btrfs_commit_transaction` during the shutdown sequence (`generic_shutdown_super` -> `btrfs_kill_super`).
This is a **kernel bug in the Btrfs driver**, not a user-space application error. It typically happens when the filesystem is being unmounted (e.g., `umount`, container exit, or system shutdown) and the Btrfs transaction commit logic encounters a corrupted or inconsistent internal state.
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### **Detailed Analysis**
#### **1. Crash Location** - **RIP**: `0000000000000000` → **NULL Pointer Dereference**. - **Call Trace**: ``` btrfs_commit_transaction+0x73/0xc00 [btrfs]
sync_filesystem+0x7a/0x90 generic_shutdown_super+0x28/0x180 kill_anon_super+0x12/0x40 btrfs_kill_super+0x12/0x20 [btrfs]
deactivate_locked_super+0x2f/0xb0 cleanup_mnt+0xea/0x180 task_work_run+0x58/0xa0 exit_to_user_mode_loop+0xed/0x480 ? __x64_sys_umount+0x68/0x80 do_syscall_64+0x2a5/0xf20 entry_SYSCALL_64_after_hwframe+0x76/0x7e ``` - **Key Insight**: The crash happens in `btrfs_commit_transaction` while the kernel is trying to sync and unmount the filesystem. This suggests that during shutdown, Btrfs tried to commit a transaction but accessed a NULL pointer, likely due to: - A corrupted transaction structure. - A race condition during unmount. - A bug in the specific kernel version’s Btrfs implementation.
#### **2. Context** - **Syscall**: `__x64_sys_umount` → The crash was triggered by an `umount` system call. - **Filesystem**: Btrfs (`[btrfs]` in call trace).
- **Timing**: The crash occurred during `generic_shutdown_super`, which is called when a filesystem is being unmounted or the superblock is being destroyed.
#### **3. Possible Causes** 1. **Kernel Bug**: This is the most likely cause. Certain kernel versions have known bugs in Btrfs transaction handling during unmount. 2. **Filesystem Corruption**: If the Btrfs filesystem was already corrupted (e.g., due to a previous crash, power loss, or disk errors), the unmount process might trigger a NULL pointer dereference when trying to commit the transaction. 3. **Hardware Issues**: Faulty RAM or disk can cause memory corruption, leading to NULL pointers. 4. **Driver/Module Bug**: If you are using a custom or out-of-tree Btrfs module, it might be buggy.
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### **Recommended Actions**
#### **1. Check for Known Bugs** - Identify your **kernel version** (`uname -r`). - Search for known Btrfs unmount crashes in your kernel version: ```bash dmesg | grep -i btrfs journalctl -k | grep -i btrfs ``` - Check if there are known fixes in newer kernel versions. If you are on an older kernel, consider upgrading.
#### **2. Check Filesystem Health** - **Do NOT force unmount** if possible, as it may worsen corruption. - Run a Btrfs filesystem check: ```bash sudo btrfs check /dev/your_btrfs_device ``` - If errors are found, you may need to restore from backup. - If no errors are found, the issue is likely a kernel bug.
#### **3. Update Kernel** - If this is a known bug, updating to a newer kernel version may fix it. - For Ubuntu/Debian: ```bash sudo apt update sudo apt install linux-generic-hwe-22.04 # Adjust for your version ``` - For RHEL/CentOS: ```bash sudo yum update kernel ```
#### **4. Check Hardware** - Run memory tests (e.g
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