CVE-2026-74315lockd: Avoid hashing uninitialized bytes in nlm4svc_lookup_file()

Official description

In the Linux kernel, the following vulnerability has been resolved: lockd: Avoid hashing uninitialized bytes in nlm4svc_lookup_file() file_hash() digests the first LOCKD_FH_HASH_SIZE bytes of nfs_fh.data when bucketing nlm_files[], independent of fh.size. Commit 3de744ee4e45 ("lockd: Use xdrgen XDR functions for the NLMv4 TEST procedure") set .pc_argzero to zero for the converted procedures and moved file-handle population into nlm4svc_lookup_file(), which copies only xdr_lock->fh.len bytes into lock->fh.data. When an NLMv4 client presents a file handle shorter than LOCKD_FH_HASH_SIZE, bytes fh.len..31 retain whatever the argument buffer held from an earlier request. The same wire handle then hashes to different buckets across calls; nlm_lookup_file() misses the existing nlm_file entry, and lock-state lookups fail. Zero only the tail bytes that file_hash() would otherwise consume. Handles of LOCKD_FH_HASH_SIZE or larger already populate every byte that file_hash() reads.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/686c2434f9f16b87aeed18d76cc562df9f2695ab
• https://git.kernel.org/stable/c/6e4c62caecf792e8a15ad9bc7f371e57c17e3302