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In the Linux kernel, the following vulnerability has been resolved:
io-wq: check that the predecessor is hashed in io_wq_remove_pending()
io_wq_remove_pending() needs to fix up wq->hash_tail[] if the cancelled
work was the tail of its hash bucket. When doing this, it checks whether
the preceding entry in acct->work_list has the same hash value, but
never checks that the predecessor is hashed at all. io_get_work_hash()
is simply atomic_read(&work->flags) >> IO_WQ_HASH_SHIFT, and the hash
bits are never set for non-hashed work, so it returns 0. Thus, when a
hashed bucket-0 work is cancelled while a non-hashed work is its list
predecessor, the check spuriously passes and a pointer to the non-hashed
io_kiocb is stored in wq->hash_tail[0].
Because non-hashed work is dequeued via the fast path in
io_get_next_work(), which never touches hash_tail[], the stale pointer
is never cleared. Therefore, after the non-hashed io_kiocb completes and
is freed back to req_cachep, wq->hash_tail[0] is a dangling pointer. The
io_wq is per-task (tctx->io_wq) and survives ring open/close, so the
dangling pointer persists for the lifetime of the task; the next hashed
bucket-0 enqueue dereferences it in io_wq_insert_work() and
wq_list_add_after() writes through freed memory.
Add the missing io_wq_is_hashed() check so a non-hashed predecessor
never inherits a hash_tail[] slot.
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Title: Linux, Description: En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:
io-wq: verificar que el predecesor esté hasheado en io_wq_remove_pending()
io_wq_remove_pending() necesita corregir wq->hash_tail[] si el trabajo cancelado era la cola de su cubo hash. Al hacer esto, verifica si la entrada precedente en acct->work_list tiene el mismo valor hash, pero nunca verifica que el predecesor esté hasheado en absoluto. io_get_work_hash() es simplemente atomic_read(&work->flags) >> IO_WQ_HASH_SHIFT, y los bits hash nunca se establecen para trabajos no hasheados, por lo que devuelve 0. Así, cuando un trabajo hasheado del cubo 0 es cancelado mientras que un trabajo no hasheado es su predecesor en la lista, la verificación pasa de forma espuria y un puntero al io_kiocb no hasheado se almacena en wq->hash_tail[0].
Debido a que el trabajo no hasheado se desencola a través de la ruta rápida en io_get_next_work(), que nunca toca hash_tail[], el puntero obsoleto nunca se borra. Por lo tanto, después de que el io_kiocb no hasheado se completa y se libera de nuevo a req_cachep, wq->hash_tail[0] es un puntero colgante. El io_wq es por tarea (tctx->io_wq) y sobrevive a la apertura/cierre del anillo, por lo que el puntero colgante persiste durante la vida útil de la tarea; la siguiente encolación hasheada del cubo 0 lo desreferencia en io_wq_insert_work() y wq_list_add_after() escribe a través de memoria liberada.
Añadir la verificación io_wq_is_hashed() faltante para que un predecesor no hasheado nunca herede una ranura hash_tail[].
Initial Analysis by NIST7/08/2026 10:46:03 AM
Action
Type
Old Value
New Value
Added
CWE
CWE-416
Added
CPE Configuration
OR
*cpe:2.3:o:linux:linux_kernel:5.9:-:*:*:*:*:*:*
*cpe:2.3:o:linux:linux_kernel:5.9:rc7:*:*:*:*:*:*
*cpe:2.3:o:linux:linux_kernel:5.9:rc8:*:*:*:*:*:*
*cpe:2.3:o:linux:linux_kernel:5.9:rc4:*:*:*:*:*:*
*cpe:2.3:o:linux:linux_kernel:5.9:rc5:*:*:*:*:*:*
*cpe:2.3:o:linux:linux_kernel:5.9:rc6:*:*:*:*:*:*
*cpe:2.3:o:linux:linux_kernel:5.9:rc3:*:*:*:*:*:*
*cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* versions from (including) 5.8.6 up to (excluding) 5.9
*cpe:2.3:o:linux:linux_kernel:7.1:rc1:*:*:*:*:*:*
*cpe:2.3:o:linux:linux_kernel:7.1:rc2:*:*:*:*:*:*
*cpe:2.3:o:linux:linux_kernel:7.1:rc3:*:*:*:*:*:*
*cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* versions from (including) 6.7 up to (excluding) 6.12.91
*cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* versions from (including) 6.13 up to (excluding) 6.18.33
*cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* versions from (including) 6.19 up to (excluding) 7.0.10
*cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* versions from (including) 5.9.1 up to (excluding) 6.6.141
New CVE Received from kernel.org6/08/2026 12:16:40 PM
Action
Type
Old Value
New Value
Added
Description
In the Linux kernel, the following vulnerability has been resolved:
io-wq: check that the predecessor is hashed in io_wq_remove_pending()
io_wq_remove_pending() needs to fix up wq->hash_tail[] if the cancelled
work was the tail of its hash bucket. When doing this, it checks whether
the preceding entry in acct->work_list has the same hash value, but
never checks that the predecessor is hashed at all. io_get_work_hash()
is simply atomic_read(&work->flags) >> IO_WQ_HASH_SHIFT, and the hash
bits are never set for non-hashed work, so it returns 0. Thus, when a
hashed bucket-0 work is cancelled while a non-hashed work is its list
predecessor, the check spuriously passes and a pointer to the non-hashed
io_kiocb is stored in wq->hash_tail[0].
Because non-hashed work is dequeued via the fast path in
io_get_next_work(), which never touches hash_tail[], the stale pointer
is never cleared. Therefore, after the non-hashed io_kiocb completes and
is freed back to req_cachep, wq->hash_tail[0] is a dangling pointer. The
io_wq is per-task (tctx->io_wq) and survives ring open/close, so the
dangling pointer persists for the lifetime of the task; the next hashed
bucket-0 enqueue dereferences it in io_wq_insert_work() and
wq_list_add_after() writes through freed memory.
Add the missing io_wq_is_hashed() check so a non-hashed predecessor
never inherits a hash_tail[] slot.