CVE-2026-89547

Status: UPDATED  |  Advisory ID: CVE-2026-89547

Key Details

Affected Products, Subsystems & Sectors

What to Know

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

SUNRPC: Check svc pool percpu counter allocation

__svc_create() initializes three per-pool percpu_counter stats and

ignores every return value. On SMP, percpu_counter_init() fails when

__alloc_percpu_gfp() cannot satisfy the allocation, leaving the failed

counter with fbc->counters == NULL and its embedded raw_spinlock_t,

list_head, and count never initialized. __svc_create() returns the

half-constructed svc_serv to nfsd, lockd, or the NFS callback service

anyway.

Once that service is live, the hot-path increments in

svc_xprt_enqueue(), svc_handle_xprt(), and

svc_pool_wake_idle_thread() reach a counter whose backing pointer is

NULL. The pointer is a per-cpu offset, so the access does not fault:

it resolves to offset zero of the current CPU's per-cpu area and

silently corrupts whatever variable lives there. A

/proc/fs/nfsd/pool_stats read walks the same NULL per-cpu storage and

returns garbage, and on CONFIG_DEBUG_SPINLOCK or lockdep it splats on

the never-initialized lock.

Creating the broken service requires a percpu allocation failure during

RPC server startup, so it is reachable only by a local administrator

under memory pressure or fault injection; a remote peer cannot induce

the bad state on its own.

Check each percpu_counter_init() return value in __svc_create() and

fail when an allocation fails, unwinding the counters already set up

in the current pool and in every pool initialized before it. A

discrete percpu_counter_destroy() per counter at teardown frees each

per-cpu allocation exactly once. (NVD)

What to Do

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

References