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The vulnerability exists in the `mlx4_en_create_rx_ring` function within the Linux kernel’s mlx4 Ethernet driver. This function is responsible for setting up a receive ring buffer for network packets. It calls `page_pool_create()` to allocate a memory pool. The `page_pool_create()` function returns an error pointer (via ERR_PTR) on failure, not a NULL pointer. The original buggy code incorrectly used a NULL check (if (!pool)) to test for allocation failure. If `page_pool_create()` failed and returned an error pointer, the NULL check would pass, incorrectly treating the error pointer as a valid one. This leads to a NULL pointer dereference later when the code attempts to use this invalid pointer, potentially causing a kernel crash or system instability. The fix replaces the `NULL` check with the correct `IS_ERR()` function to properly identify error pointers from this function.
Platform: Linux Kernel
Version: mlx4 driver
Vulnerability : NULL pointer dereference
Severity: Medium
date: 2025-09-19
Prediction: 2026-Q1
What Undercode Say:
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Check current kernel version uname -r List loaded kernel modules, filter for mlx4 lsmod | grep mlx4 Check if the system uses Mellanox network hardware lspci | grep -i mellanox
// Code snippet showing the vulnerable pattern (simplified)
pool = page_pool_create(...);
if (!pool) { // BUG: Wrong check for page_pool_create's error
return -ENOMEM;
}
// Correct check should be:
if (IS_ERR(pool)) {
return PTR_ERR(pool);
}
How Exploit:
Exploitation Method
Local privilege escalation is not feasible. An attacker with existing local access and low privileges can trigger the bug. They must cause the `page_pool_create()` function to fail, returning an error pointer. This might be achieved by exhausting specific memory resources or manipulating driver state. The subsequent kernel code dereferences this invalid pointer. This results in a kernel oops or panic, causing a denial of service (system crash).
Protection from this CVE
Mitigation Strategies
Update the Linux kernel to a version containing the fix. Major distributions like Ubuntu, Red Hat, and SUSE have marked their supported kernels as “Not affected,” indicating the fix is backported. If the mlx4 driver is not needed, prevent it from loading by blacklisting the module. For unpatched kernels, restrict local user access to systems using Mellanox ConnectX-3 or earlier hardware requiring this driver. Regularly monitor kernel security advisories from your distribution vendor.
Impact
Consequences
The primary impact is a denial of service due to system instability or crash. Confidentiality and integrity of data are not impacted. The attack requires local access with low privileges, limiting its scope. Systems using the affected mlx4 Ethernet driver for Mellanox network devices are vulnerable. The CVSS v3.1 score is 5.5 (Medium), with High impact on Availability. The vulnerability is classified under CWE-476: NULL Pointer Dereference.
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Sources:
Reported By: nvd.nist.gov
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