CVE-2026-52999: netfilter: nfnetlink_osf: fix out-of-bounds read on option matching

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

netfilter: nfnetlinkosf: fix out-of-bounds read on option matching

In nfosfmatch(), the nfosfhdrctx structure is initialized once and passed by reference to nfosfmatchone() for each fingerprint checked. During TCP option parsing, nfosfmatchone() advances the shared ctx->optp pointer.

If a fingerprint perfectly matches, the function returns early without restoring ctx->optp to its initial state. If the user has configured NFOSFLOGLEVELALL, the loop continues to the next fingerprint. However, because ctx->optp was not restored, the next call to nfosfmatchone() starts parsing from the end of the options buffer. This causes subsequent matches to read garbage data and fail immediately, making it impossible to log more than one match or logging incorrect matches.

Instead of using a shared ctx->optp pointer, pass the context as a constant pointer and use a local pointer (optp) for TCP option traversal. This makes nfosfmatchone() strictly stateless from the caller's perspective, ensuring every fingerprint check starts at the correct option offset.