tcp: fix potential memory corruption
authorEric Dumazet <edumazet@google.com>
Wed, 2 Nov 2016 14:53:17 +0000 (07:53 -0700)
committerDavid S. Miller <davem@davemloft.net>
Thu, 3 Nov 2016 19:33:30 +0000 (15:33 -0400)
Imagine initial value of max_skb_frags is 17, and last
skb in write queue has 15 frags.

Then max_skb_frags is lowered to 14 or smaller value.

tcp_sendmsg() will then be allowed to add additional page frags
and eventually go past MAX_SKB_FRAGS, overflowing struct
skb_shared_info.

Fixes: 5f74f82ea34c ("net:Add sysctl_max_skb_frags")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Hans Westgaard Ry <hans.westgaard.ry@oracle.com>
Cc: HÃ¥kon Bugge <haakon.bugge@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
net/ipv4/tcp.c

index 3251fe71f39f2395befb0e662ca19423e6b9ea90..18238ef8135a282cd519056e78d795c336ae7714 100644 (file)
@@ -1241,7 +1241,7 @@ new_segment:
 
                        if (!skb_can_coalesce(skb, i, pfrag->page,
                                              pfrag->offset)) {
-                               if (i == sysctl_max_skb_frags || !sg) {
+                               if (i >= sysctl_max_skb_frags || !sg) {
                                        tcp_mark_push(tp, skb);
                                        goto new_segment;
                                }