From 4672694bd4f1aebdab0ad763ae4716e89cb15221 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Mon, 30 Jul 2018 21:50:29 -0700 Subject: [PATCH] ipv4: frags: handle possible skb truesize change ip_frag_queue() might call pskb_pull() on one skb that is already in the fragment queue. We need to take care of possible truesize change, or we might have an imbalance of the netns frags memory usage. IPv6 is immune to this bug, because RFC5722, Section 4, amended by Errata ID 3089 states : When reassembling an IPv6 datagram, if one or more its constituent fragments is determined to be an overlapping fragment, the entire datagram (and any constituent fragments) MUST be silently discarded. Fixes: 158f323b9868 ("net: adjust skb->truesize in pskb_expand_head()") Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller --- net/ipv4/ip_fragment.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/net/ipv4/ip_fragment.c b/net/ipv4/ip_fragment.c index 8e9528ebaa8e1a..d14d741fb05e57 100644 --- a/net/ipv4/ip_fragment.c +++ b/net/ipv4/ip_fragment.c @@ -383,11 +383,16 @@ static int ip_frag_queue(struct ipq *qp, struct sk_buff *skb) int i = end - next->ip_defrag_offset; /* overlap is 'i' bytes */ if (i < next->len) { + int delta = -next->truesize; + /* Eat head of the next overlapped fragment * and leave the loop. The next ones cannot overlap. */ if (!pskb_pull(next, i)) goto err; + delta += next->truesize; + if (delta) + add_frag_mem_limit(qp->q.net, delta); next->ip_defrag_offset += i; qp->q.meat -= i; if (next->ip_summed != CHECKSUM_UNNECESSARY)