CVE-2026-89690

Status: UPDATED  |  Advisory ID: CVE-2026-89690

Key Details

Affected Products, Subsystems & Sectors

What to Know

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

nfsd: defer vfree of compound ops to fix rpc_status UAF

The rpc_status netlink dumpit walks every in-flight svc_rqst under

rcu_read_lock and, for NFSv4 requests, reads opnums out of

args->ops[]. But args->ops is a separate vmalloc buffer freed

synchronously by vfree() in nfsd4_release_compoundargs() at the end

of every compound. The dumpit's rcu_read_lock pins the svc_rqst

struct itself (freed via kfree_rcu), but nothing defers the vfree

of the ops buffer across the RCU grace period. A concurrent compound

completion can therefore free the buffer while the dumpit is reading

it — a use-after-free on vmalloc memory.

The trailing seqcount recheck (smp_load_acquire of rq_status_counter)

cannot undo a load that already retired against freed memory.

Fix by replacing vfree(args->ops) with kvfree_rcu_mightsleep(), which

defers the free until after an RCU grace period. This makes the

existing rcu_read_lock in the dumpit sufficient to protect the read.

The tradeoff is that completed compound ops buffers (up to

200 * sizeof(struct nfsd4_op)) persist in memory slightly longer,

across one grace period, before being reclaimed. (NVD)

What to Do

Monitor Linux's web page for any future patch releases.

References