CVE-2026-43475 in Linux
Zusammenfassung
von VulDB • 14.05.2026
Based on the kernel stack trace provided, here is an analysis of the issue:
### **Summary** This is **not a crash or panic**. It is a **normal kernel stack trace** captured during a system call (`write()`), likely for debugging, profiling, or due to a warning/lockdep check. The system is functioning correctly; it is simply performing a file write operation on an **ext4** filesystem.
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### **Detailed Breakdown**
#### **1. What is happening?** - A user-space process called the `write()` system call (`ksys_write`). - This triggered a write operation on a file mounted on an **ext4** filesystem. - The kernel is preparing to write data to disk using **delayed allocation** (`ext4_da_write_begin`), which is the default and most efficient mode for ext4. - The operation involves submitting a bio (block I/O request) via `submit_bio_noacct_nocheck`.
#### **2. Key Functions in the Stack** | Function | Description | |----------|-------------| | `do_syscall_64` | Entry point for 64-bit system calls. | | `ksys_write` | The `write()` system call handler. | | `vfs_write` | Virtual File System write layer. | | `ext4_buffered_write_iter` | ext4-specific buffered write handler. | | `ext4_da_write_begin` | **Delayed Allocation** write begin. This is where ext4 decides which blocks to allocate for the write. | | `ext4_block_write_begin` | Core block write begin logic. | | `ext4_read_bh_lock` | Locking mechanism for buffer heads (likely related to read-ahead or metadata locking). | | `submit_bio_noacct_nocheck` | Submits the I/O request to the block layer. |
#### **3. Why was this captured?** Since there is no `BUG()`, `WARN()`, or `Oops` in the trace, this stack was likely captured for one of these reasons: - **Lockdep Warning**: A lock dependency issue was detected during the write. - **RCU Warning**: `rcu_is_watching` appears multiple times, which might indicate an RCU-related debug check. - **Profiling/Tracing**: Tools like `ftrace`, `perf`, or `bpftrace` were tracing system calls. - **Hang/Deadlock Debugging**: If the system was stuck, this stack shows what the CPU was doing before the hang.
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### **Is This a Problem?** - **No**, if this is just a log entry from a normal operation. - **Yes**, if: - The system is **hanging** or **freezing** at this point. - There is a **preceding `WARNING:` or `BUG:` message** in the dmesg log. - You are seeing **I/O errors** or **slow disk performance**.
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### **Recommendations** 1. **Check for Preceding Errors**: Look at `dmesg` or `journalctl` for any `WARNING:`, `BUG:`, or `EXT4-fs error` messages **before** this stack trace. 2. **Check Disk Health**: Run `smartctl -a /dev/sdX` to check for disk errors. 3. **Check for Lockdep Issues**: If you see `possible circular locking dependency` or similar, it’s a kernel lock issue, not a disk issue. 4. **Update Kernel**: If this is part of a known bug, check if your kernel version has a fix for ext4 write delays or lockdep warnings.
If you are experiencing a **system hang** or **crash**, please provide: - The **full dmesg log** (especially before this stack). - The **kernel version** (`uname -r`). - Whether this happens **consistently** or randomly.
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