Harden msgr2.1 frame segment length checks

[Mrcopytuo]

Summary

Harden msgr2.1 frame segment length checks in libceph.

This patch applies the upstream change from commit[a282a2f10539dce2aa619e71e1817570d557fc97(https://github.com/torvalds/linux/commit/a282a2f10539dce2aa619e71e1817570d557fc97).

Details

• Strengthen validation of msgr2.1 frame segment lengths in the Ceph messenger implementation.
• Ensure correct signedness handling when checking frame segment lengths in decode_preamble(), because ceph_frame_desc::fd_lens is an int array and previously unsigned-style checks could allow invalid values.

Context

Original commit was authored by Ilya Dryomov and merged upstream to correct frame segment checks that assumed unsigned lengths. The fix prevents potential malformed or malicious msgr2.1 input from bypassing validation due to incorrect type handling.

Impact

Improves robustness and correctness of Ceph msgr2.1 frame parsing.