CVE-2026-63926: Undefined Security Weakness

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

bpf: sockmap: fix tail fragment offset in bpf_msg_push_data

When bpf_msg_push_data() inserts data in the middle of a scatterlist entry, it splits the original entry into a left fragment and a right fragment.

The right fragment offset is page-local, but the code advances it with `start`, which is the message-global insertion point. For inserts into a non-first SG entry, this over-advances the offset and leaves the split layout inconsistent.

Advance the right fragment offset by the fragment-local delta, `start - offset`, which matches the length removed from the front of the original entry.