CVE-2025-38714 in Linux
要約
〜によって VulDB • 2026年05月12日
Based on the kernel log snippet provided, here is an analysis of the issue:
### **Summary** This is a **KASAN (Kernel Address Sanitizer)** report indicating a **use-after-free** or **invalid memory access** in the `hfsplus` filesystem driver. The crash occurs in `hfsplus_delete_all_attrs()` during a call to `hfsplus_brec_find()`, which eventually leads to a fault in `hfsplus_bnode_create()`.
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### **Key Details from the Log**
1. **Crash Location**: - `RIP: 0x7f6fdf4c3167` → This is inside the `hfsplus` kernel module (likely `hfsplus_bnode_create` or related code). - The instruction pointer is in user-space-like address space (`0x7f...`), which is typical for kernel modules loaded at high addresses.
2. **Call Trace (Relevant Part)**: ``` hfsplus_delete_all_attrs+0x23b/0x3 → hfsplus_brec_find+0x2b0/0x520 → hfsplus_bnode_find+0x2d0/0xd10 → __hfs_bnode_create+0x107/0x890 → __kmalloc_noprof+0x205/0x550 → __kasan_kmalloc+0xaa/0xb0 ``` - The function `hfsplus_delete_all_attrs()` is trying to find a record (`hfsplus_brec_find`), which requires finding/creating a b-tree node (`hfsplus_bnode_find` → `__hfs_bnode_create`). - The allocation (`__kmalloc`) is being tracked by KASAN, suggesting that the memory being accessed was previously freed or is invalid.
3. **KASAN Allocation Trace**: - The memory was allocated via `__kmalloc_noprof` → `__kasan_kmalloc`. - KASAN is detecting that this memory is being accessed after it was freed (use-after-free) or is out of bounds.
4. **Registers**: - `RAX: ffffffffffffffda` → This is `-42` in two's complement, which is `ERR_PTR(-42)` in Linux kernel. This suggests that an error pointer was returned from a previous function call, but it was dereferenced as if it were a valid pointer. - `ERR_PTR(-42)` corresponds to `-EINVAL` (Invalid argument).
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### **Root Cause Analysis**
The most likely cause is:
> **A function returned an error pointer (`ERR_PTR(-42)`), but the caller did not check for it and dereferenced it, leading to a crash.**
In the `hfsplus` driver, `hfsplus_bnode_find()` or `__hfs_bnode_create()` may have failed (e.g., due to invalid parameters or I/O error) and returned `ERR_PTR(-EINVAL)`. The caller (`hfsplus_brec_find()` or `hfsplus_delete_all_attrs()`) then used this invalid pointer, causing a page fault or KASAN violation.
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### **How to Fix**
1. **Check for Error Pointers**: - In `hfsplus_brec_find()` and `hfsplus_delete_all_attrs()`, ensure that return values from `hfsplus_bnode_find()` and `__hfs_bnode_create()` are checked using `IS_ERR()` before dereferencing.
Example fix: ```c struct hfs_bnode *node = hfsplus_bnode_find(...); if (IS_ERR(node)) {
return PTR_ERR(node); } ```
2. **Debugging Steps**: - Enable `CONFIG_KASAN` and `CONFIG_KASAN_INLINE` for better error reporting. - Use `CONFIG_DEBUG_INFO` to get line numbers in the crash trace. - Check if the issue is reproducible with a specific file or directory on an HFS+ filesystem.
3. **Kernel Version**: - This bug may have been fixed in newer kernels. Check if your kernel version is up-to-date. - Search for patches related to `hfsplus_delete_all_attrs` and `hfsplus_bnode_find` in the Linux kernel git log.
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### **Conclusion** The crash is due to **dereferencing an error pointer** in the `hfsplus` filesystem driver. The fix involves adding proper error checks for `IS_ERR()` before using pointers returned by `hfsplus_bnode_find()` and related functions.
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