CVE-2023-53718 in Linux
الملخص
بحسب VulDB • 16/06/2026
Based on the kernel oops log provided, here is a detailed analysis of the crash:
### **1. Summary of the Crash** - **Type of Crash**: Kernel NULL pointer dereference (`Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000`). - **Function**: `rb_update_pages+0x1a8/0x3f8` - **Workqueue**: `events` → `update_pages_handler` - **CPU/Process**: CPU 0, PID 9, `kworker/0:1` - **Kernel Version**: `6.5.0-rc1-00276-g20edcec23f92` (a development/RC kernel) - **Hardware**: `linux,dummy-virt` (QEMU virtual machine)
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### **2. Root Cause Analysis**
#### **A. The Faulting Instruction** The crash occurs in `rb_update_pages()` at offset `+0x1a8`. This function is part of the **Red-Black Tree (RB-tree)** implementation in the Linux kernel, specifically used for managing memory pages (e.g., in `mm/rbtree.c` or related memory management code).
The NULL pointer dereference at address `0x0` means the code tried to access a member of a pointer that was `NULL`.
#### **B. Likely Scenario** In `rb_update_pages()`, the code typically traverses or modifies RB-tree nodes. A common pattern is: ```c struct rb_node *node = ...; // ... node->rb_left = ...; // Crash if node is NULL ``` Or: ```c struct page *page = rb_entry(node, struct page, rb_node); // ... page->flags = ...; // Crash if page is NULL ```
Given the workqueue name `update_pages_handler`, this is likely related to **memory compaction**, **page reclaim**, or **huge page management**.
#### **C. Why is the Pointer NULL?** 1. **Race Condition**: Another thread may have freed or removed the node/page from the tree before this worker thread accessed it. 2. **Invalid Tree State**: The RB-tree might be corrupted due to a previous bug (e.g., improper insertion/deletion). 3. **Bug in `rb_update_pages()`**: The function may not properly check for `NULL` before dereferencing.
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### **3. Debugging Steps**
#### **Step 1: Get Full Backtrace** The log is truncated. You need the full call stack to see who called `rb_update_pages()`. Use: ```bash dmesg | grep -A 50 "rb_update_pages" ``` Or check `/var/log/kern.log` or `journalctl -k`.
#### **Step 2: Check for Recent Changes** Since this is a **6.5-rc1** kernel, it’s a development version. Check if there are recent commits to: - `mm/rbtree.c` - `mm/compaction.c` - `mm/huge_memory.c`
#### **Step 3: Reproduce the Issue** - Run the workload that triggers `update_pages_handler`. - Use `CONFIG_DEBUG_VM` and `CONFIG_DEBUG_RB_TREE` enabled in the kernel config to catch RB-tree corruption early.
#### **Step 4: Inspect the Code** Look at `rb_update_pages()` in `mm/rbtree.c` (or similar). Find the line at offset `+0x1a8` and check what pointer is being dereferenced.
Example (hypothetical): ```c static void rb_update_pages(struct rb_root *root, ...) {
struct rb_node *node = root->rb_node; while (node) {
struct page *page = rb_entry(node, struct page, rb_node); // ... if (page->flags & ...) { // <-- Crash here if page is NULL
// ... } node = rb_next(node); } } ```
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### **4. Potential Fixes**
1. **Add NULL Checks**: Ensure all pointers are validated before dereferencing: ```c if (!page) {
pr_err("NULL page in rb_update_pages\n"); return; } ```
2. **Fix Race Conditions**: If the node is being freed concurrently, ensure proper locking (e.g., `spin_lock`, `mutex`) is held during tree traversal.
3. **Update Kernel**: Since this is an RC kernel, check if the bug has been fixed in later versions (
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