CVE-2024-50188

What it actually does

Incorrect invocation of linkmode_set_bit() with a bitmask (1 << 10) instead of a bit index (10) in the DP83869 PHY driver during fiber-port configuration overwrites adjacent kernel memory such as the priv pointer on arm64.

Why it matters to the business

Systems using the affected PHY on fiber links may experience kernel instability, crashes, or loss of network connectivity, increasing downtime and operational risk on Linux-based network appliances and servers.

How an attack unfolds

An attacker with local access triggers the fiber-port configuration path in the DP83869 driver; the erroneous linkmode_set_bit call immediately corrupts in-structure pointers, which can be leveraged for denial of service or further memory-safety violations.

How to fix it

Update the Linux kernel to a version containing commit 21b5af7f0c99b3bf1fd02016e6708b613acbcaf4 or later; remove the unnecessary linkmode_set_bit line from the dp83869 driver if backporting is required.

How to confirm the fix worked

Confirm the driver source no longer contains the erroneous linkmode_set_bit(1 << 10, ...) call and that the fixed commit is present in the running kernel tree; test fiber-port configuration on DP83869 hardware.

Typical attack path

1. Obtain local execution context on the target host
2. Cause the DP83869 driver to configure the fiber interface (e.g., via ethtool or interface bring-up)
3. Trigger the faulty linkmode_set_bit call leading to memory corruption
4. Exploit resulting pointer corruption for crash or privilege escalation

How to detect it

Inspect kernel logs for oops or panic messages mentioning dp83869 or linkmode_set_bit near fiber configuration events; correlate with interface bring-up timestamps.

What your security team should do

• Prioritize kernel updates on all systems exposing DP83869 PHYs
• Review and restrict local user ability to reconfigure network interfaces where feasible
• Monitor for kernel oops or crashes referencing dp83869 after fiber configuration changes