net-timestamp: avoid use-after-free in ip_recv_error
[ Upstream commit 1862d6208db0aeca9c8ace44915b08d5ab2cd667 ]
Syzkaller reported a use-after-free in ip_recv_error at line
info->ipi_ifindex = skb->dev->ifindex;
This function is called on dequeue from the error queue, at which
point the device pointer may no longer be valid.
Save ifindex on enqueue in __skb_complete_tx_timestamp, when the
pointer is valid or NULL. Store it in temporary storage skb->cb.
It is safe to reference skb->dev here, as called from device drivers
or dev_queue_xmit. The exception is when called from tcp_ack_tstamp;
in that case it is NULL and ifindex is set to 0 (invalid).
Do not return a pktinfo cmsg if ifindex is 0. This maintains the
current behavior of not returning a cmsg if skb->dev was NULL.
On dequeue, the ipv4 path will cast from sock_exterr_skb to
in_pktinfo. Both have ifindex as their first element, so no explicit
conversion is needed. This is by design, introduced in commit
0b922b7a829c ("net: original ingress device index in PKTINFO"). For
ipv6 ip6_datagram_support_cmsg converts to in6_pktinfo.
Fixes: 829ae9d61165 ("net-timestamp: allow reading recv cmsg on errqueue with origin tstamp")
Reported-by: Andrey Konovalov <andreyknvl@google.com>
Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/net/ipv6/datagram.c b/net/ipv6/datagram.c
index 8616d17..442ec1f 100644
--- a/net/ipv6/datagram.c
+++ b/net/ipv6/datagram.c
@@ -400,9 +400,6 @@
* At one point, excluding local errors was a quick test to identify icmp/icmp6
* errors. This is no longer true, but the test remained, so the v6 stack,
* unlike v4, also honors cmsg requests on all wifi and timestamp errors.
- *
- * Timestamp code paths do not initialize the fields expected by cmsg:
- * the PKTINFO fields in skb->cb[]. Fill those in here.
*/
static bool ip6_datagram_support_cmsg(struct sk_buff *skb,
struct sock_exterr_skb *serr)
@@ -414,14 +411,9 @@
if (serr->ee.ee_origin == SO_EE_ORIGIN_LOCAL)
return false;
- if (!skb->dev)
+ if (!IP6CB(skb)->iif)
return false;
- if (skb->protocol == htons(ETH_P_IPV6))
- IP6CB(skb)->iif = skb->dev->ifindex;
- else
- PKTINFO_SKB_CB(skb)->ipi_ifindex = skb->dev->ifindex;
-
return true;
}