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CVE-2022-49814

Estado: ModificadaMedia (4.7)—

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

kcm: close race conditions on sk_receive_queue

sk->sk_receive_queue is protected by skb queue lock, but for KCM sockets its RX path takes mux->rx_lock to protect more than just skb queue. However, kcm_recvmsg() still only grabs the skb queue lock, so race conditions still exist.

We can teach kcm_recvmsg() to grab mux->rx_lock too but this would introduce a potential performance regression as struct kcm_mux can be shared by multiple KCM sockets.

So we have to enforce skb queue lock in requeue_rx_msgs() and handle skb peek case carefully in kcm_wait_data().

Leer descripción completaMostrar menos

Fortunately, skb_recv_datagram() already handles it nicely and is widely used by other sockets, we can just switch to skb_recv_datagram() after getting rid of the unnecessary sock lock in kcm_recvmsg() and kcm_splice_read(). Side note: SOCK_DONE is not used by KCM sockets, so it is safe to get rid of this check too.

I ran the original syzbot reproducer for 30 min without seeing any issue.

CVSS

Probabilidad de explotación (EPSS)

EPSS (Exploit Prediction Scoring System, de FIRST) estima la probabilidad de que una vulnerabilidad sea explotada en 30 días. Complementa a CVSS (impacto) y a CISA KEV (explotación confirmada).

Tecnologías afectadas (1)

Linux — Linux Kernel

CWE

Referencias

JSON original (NVD)

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      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nkcm: close race conditions on sk_receive_queue\n\nsk->sk_receive_queue is protected by skb queue lock, but for KCM\nsockets its RX path takes mux->rx_lock to protect more than just\nskb queue. However, kcm_recvmsg() still only grabs the skb queue\nlock, so race conditions still exist.\n\nWe can teach kcm_recvmsg() to grab mux->rx_lock too but this would\nintroduce a potential performance regression as struct kcm_mux can\nbe shared by multiple KCM sockets.\n\nSo we have to enforce skb queue lock in requeue_rx_msgs() and handle\nskb peek case carefully in kcm_wait_data(). Fortunately,\nskb_recv_datagram() already handles it nicely and is widely used by\nother sockets, we can just switch to skb_recv_datagram() after\ngetting rid of the unnecessary sock lock in kcm_recvmsg() and\nkcm_splice_read(). Side note: SOCK_DONE is not used by KCM sockets,\nso it is safe to get rid of this check too.\n\nI ran the original syzbot reproducer for 30 min without seeing any\nissue."
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    {
      "lang": "es",
      "value": "En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: kcm: condiciones de ejecución cerradas en sk_receive_queue. sk->sk_receive_queue está protegido por el bloqueo de cola skb, pero para los sockets KCM su ruta RX toma mux->rx_lock para proteger más que solo la cola skb. Sin embargo, kcm_recvmsg() todavía solo captura el bloqueo de cola skb, por lo que las condiciones de ejecución aún existen. Podemos enseñar a kcm_recvmsg() a capturar también mux->rx_lock, pero esto introduciría una posible regresión del rendimiento, ya que la estructura kcm_mux puede ser compartida por varios sockets KCM. Por lo tanto, debemos aplicar el bloqueo de cola skb en requeue_rx_msgs() y manejar el caso de skb peek con cuidado en kcm_wait_data(). Afortunadamente, skb_recv_datagram() ya lo gestiona correctamente y es ampliamente utilizado por otros sockets. Podemos cambiar a skb_recv_datagram() tras eliminar el bloqueo de sock innecesario en kcm_recvmsg() y kcm_splice_read(). Nota: Los sockets KCM no utilizan SOCK_DONE, por lo que también es seguro omitir esta comprobación. Ejecuté el reproductor syzbot original durante 30 minutos sin observar ningún problema."
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