cxgb4 DeregSkb DoubleFree

Vulnerability analysis

The cxgb4 RDMA driver mishandles a preallocated socket buffer on error paths during memory region registration and deregistration. When the network device is in a fatal error state or when internal allocations fail, the write path returns early without freeing the caller's buffer, causing a leak in the deregistration path; conversely, when an initial registration succeeds but a follow-up step fails, the cleanup routine consumes the buffer and then the error handler frees it again, producing a double free. The fix makes the write path the sole owner of the buffer — freeing it on every early return before handing it to the transmit layer — and removes the redundant free in the caller's error path after the cleanup routine has already consumed it. This is reachable locally through the RDMA verbs interface on systems equipped with Chelsio T4/T5/T6 network hardware, requiring access to the RDMA device (typically root or membership in the rdma group).