CVE-2026-89691nfsd: clear opcnt on compound arg release to prevent OOB read

Official description

In the Linux kernel, the following vulnerability has been resolved: nfsd: clear opcnt on compound arg release to prevent OOB read nfsd4_release_compoundargs() resets args->ops to the inline iops[8] array when the dynamically-allocated ops buffer is freed, but leaves args->opcnt at its original value (which can be up to 200 for NFSv4.1+ compounds). If rq_status_counter is stuck at an odd value (which can happen when nfsd_dispatch() hits an error path after setting it odd), the RPC status dumpit handler reads min(opcnt, 16) entries from args->ops[]. Since iops only has 8 elements and is the last field in struct nfsd4_compoundargs, reading indices 8-15 accesses adjacent slab memory and leaks it to userspace via netlink. Zero opcnt unconditionally in nfsd4_release_compoundargs() so stale compound metadata is never exposed through the status interface. [ cel: Remove the kvfree_rcu_mightsleep() sleep from the exposure window ]

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/58bcdfb2b2e412088839ae740b1a95154dc0b8d0
• https://git.kernel.org/stable/c/e879148867bd4c4cac42e063ffaffa187dddc6fe
• https://git.kernel.org/stable/c/c1a4f7b1848f95302df598217e1c7a1410c2d0c5
• https://git.kernel.org/stable/c/ae4c38555e81563b8dc5eae55ffd70f0ea97aa5a