CVE-2024-27431: Use of Uninitialized Resource

In the Linux kernel, the following vulnerability has been resolved:

cpumap: Zero-initialise xdp_rxq_info struct before running XDP program

When running an XDP program that is attached to a cpumap entry, we don't initialise the xdp_rxq_info data structure being used in the xdp_buff that backs the XDP program invocation. Tobias noticed that this leads to random values being returned as the xdp_md->rx_queue_index value for XDP programs running in a cpumap.

This means we're basically returning the contents of the uninitialised memory, which is bad. Fix this by zero-initialising the rxq data structure before running the XDP program.