CVE-2023-53718 in Linux
Riassunto
di VulDB • 03/08/2026
Based on the kernel oops log provided, here is a detailed analysis of the crash.
### **1. Summary** * **Crash Type:** Kernel NULL pointer dereference (`Unable to handle kernel NULL pointer dereference at virtual address 0x0`). * **Faulting Function:** `rb_update_pages` (part of the Red-Black tree implementation in the Linux kernel). * **Context:** Running on a worker thread (`kworker/0:1`) triggered by the `events` workqueue, specifically via `update_pages_handler`. * **Kernel Version:** 6.5.0-rc1 (development/release candidate version). * **Architecture:** ARM64 (AArch64), indicated by registers like `x29`, `pc`, and ESR/EC values.
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### **2. Key Log Analysis**
#### **A. The Faulting Instruction** ```text [ 233.729054] pc : rb_update_pages+0x1a8/0x3f8
[ 233.729334] lr : rb_update_pages+0x154/0x3f8
``` * The crash occurred inside `rb_update_pages` at offset `0x1a8`. * This function is part of the kernel's **Red-Black Tree (RB-tree)** implementation, typically used for managing memory pages or other sorted data structures.
#### **B. Cause: NULL Pointer Dereference** ```text [ 233.720486] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000
... [ 233.725592] [0000000000000000] pgd=0000000000000000, p4d=0000000000000000
``` * The CPU tried to access memory address `0x0`. * Since the Page Global Directory (PGD) and P4D are also zero, this confirms it’s a **NULL pointer dereference**, not an invalid user-space or unmapped kernel address.
#### **C. Execution Context** ```text [ 233.726007] CPU: 0 PID: 9 Comm: kworker/0:1 Tainted: G W 6.5.0-rc1...
[ 233.728225] Workqueue: events update_pages_handler
``` * The crash happened in a **kernel worker thread** (`kworker`), not in user space or an interrupt handler. * It was triggered by the `update_pages_handler` work item from the generic `events` workqueue.
#### **D. Architecture Details (ARM64)** ```text [ 233.721935] ESR = 0x0000000096000004
[ 233.722283] EC = 0x25: DABT (current EL), IL = 32 bits
... [ 233.723026] FSC = 0x04: level 0 translation fault
``` * **DABT**: Data Abort at Exception Level 1 (EL1, kernel mode). * **FSC=0x04**: Translation fault at stage 1, indicating the virtual address `0x0` is not mapped in any page table.
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### **3. Likely Root Cause**
The function `rb_update_pages` likely dereferences a pointer that was expected to be valid but is actually `NULL`. Common scenarios include:
1. **Missing Initialization:** A structure containing an RB-tree node or parent/child pointers was not properly initialized before being passed to `rb_update_pages`. 2. **Use-After-Free / Dangling Pointer:** The object holding the RB-tree data was freed, but a stale pointer remained in use by the workqueue handler. 3. **Race Condition:** In concurrent code, one thread might free or nullify a pointer while another is updating it via `rb_update_pages`. 4. **Bug in Recent Code (6.5-rc1):** Since this is an RC kernel (`6.5.0-rc1`), it may be a regression introduced recently. The function name suggests it’s related to page management, possibly in memory c
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