Linux Kernel GRE Protocol Check Vulnerability Leading to Overflow

A vulnerability in the Linux kernel's GRE (Generic Routing Encapsulation) protocol handling has been addressed. The issue arose because the ipgre_xmit function did not properly validate the checksum start after an optional skb_pull, allowing local checksum offload to potentially cause an overflow. The vulnerability was related to how CHECKSUM_PARTIAL packets were processed, particularly in an uncommon GRE path that used header operations and could be affected by BPF redirection.

Impact

The vulnerability could lead to a buffer overflow, potentially allowing for arbitrary code execution or causing a denial-of-service condition by crashing the system.