High · published September 12, 2026
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.