CVE-2026-89695

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

nfsd: cap decoded POSIX ACL count to bound sort cost

nfsd4 decode posixacl() reads a u32 entry count off the wire and passes it straight to posix acl alloc() and sort pacl range(). The latter is an O(n^2) bubble sort, so a client-chosen count drives unbounded CPU in the server's compound processing path.

nfsd4 decode posixacl() xdr stream decode u32(&count) /* uncapped u32 */ posix acl alloc(count, GFP KERNEL) sort pacl range(acl, 0, count - 1) / O(n^2) bubble sort */

The encoder side in the same file already rejects ACLs whose a count exceeds NFS ACL MAX ENTRIES, but the decoder introduced in commit 5fc51dfc2eb1 ("NFSD: Add support for XDR decoding POSIX draft ACLs") omitted the symmetric check.

Fix by rejecting a wire count greater than NFS ACL MAX ENTRIES with nfserr inval, before any allocation, so the sort is bounded by NFS ACL MAX ENTRIES^2 comparisons.

While we're in here, also fix the nfserr resource return if posix acl alloc() fails. That's not a legal error code for v4.1+. Change it to return nfserr jukebox as that's more appropriate for memory allocation failures.