Commit ac9e70b1 authored Nov 02, 2016 by Eric Dumazet Committed by David S. Miller Nov 03, 2016

tcp: fix potential memory corruption



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: 5f74f82e ("net:Add sysctl_max_skb_frags")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Hans Westgaard Ry <hans.westgaard.ry@oracle.com>
Cc: Håkon Bugge <haakon.bugge@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 9512925a

net/ipv4/tcp.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -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;
		}

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