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authorWillem de Bruijn <willemb@google.com>2017-04-12 19:24:35 -0400
committerDavid S. Miller <davem@davemloft.net>2017-04-17 12:59:22 -0400
commit1862d6208db0aeca9c8ace44915b08d5ab2cd667 (patch)
treec0cdc74a6b4246fd90bf4163a5c263f92735ccab /net/ipv6
parent1215e51edad1272e669172b26aa12aac94810c7f (diff)
net-timestamp: avoid use-after-free in ip_recv_error
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>
Diffstat (limited to 'net/ipv6')
-rw-r--r--net/ipv6/datagram.c10
1 files changed, 1 insertions, 9 deletions
diff --git a/net/ipv6/datagram.c b/net/ipv6/datagram.c
index eec27f87efac..e011122ebd43 100644
--- a/net/ipv6/datagram.c
+++ b/net/ipv6/datagram.c
@@ -405,9 +405,6 @@ static inline bool ipv6_datagram_support_addr(struct sock_exterr_skb *serr)
* 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)
@@ -419,14 +416,9 @@ static bool ip6_datagram_support_cmsg(struct sk_buff *skb,
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;
}