Em Mon, Nov 28, 2016 at 06:26:49AM -0800, Eric Dumazet escreveu: > From: Eric Dumazet <[email protected]> > > pskb_may_pull() can reallocate skb->head, we need to reload dh pointer > in dccp_invalid_packet() or risk use after free. > > Bug found by Andrey Konovalov using syzkaller. > > Signed-off-by: Eric Dumazet <[email protected]> > Reported-by: Andrey Konovalov <[email protected]>
Acked-by: Arnaldo Carvalho de Melo <[email protected]> I was about to send exactly this patch, and while looking at it I think the patch below needs to go in as well, no? To follow the advice of that Warning line there :-) From: Arnaldo Carvalho de Melo <[email protected]> pskb_may_pull() can reallocate skb->head, so we can't access iph->frag_off or risk use after free, save it to a variable and us that later. Cc: Andrey Konovalov <[email protected]> Cc: Eric Dumazet <[email protected]> Signed-off-by: Arnaldo Carvalho de Melo <[email protected]> diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c index 5ddf5cda07f4..9462070561a3 100644 --- a/net/ipv4/af_inet.c +++ b/net/ipv4/af_inet.c @@ -1198,6 +1198,7 @@ struct sk_buff *inet_gso_segment(struct sk_buff *skb, struct iphdr *iph; int proto, tot_len; int nhoff; + u16 frag_off; int ihl; int id; @@ -1213,6 +1214,7 @@ struct sk_buff *inet_gso_segment(struct sk_buff *skb, id = ntohs(iph->id); proto = iph->protocol; + frag_off = iph->frag_off; /* Warning: after this point, iph might be no longer valid */ if (unlikely(!pskb_may_pull(skb, ihl))) @@ -1233,7 +1235,7 @@ struct sk_buff *inet_gso_segment(struct sk_buff *skb, fixedid = !!(skb_shinfo(skb)->gso_type & SKB_GSO_TCP_FIXEDID); /* fixed ID is invalid if DF bit is not set */ - if (fixedid && !(iph->frag_off & htons(IP_DF))) + if (fixedid && !(frag_off & htons(IP_DF))) goto out; }
