ipv4: frags: handle possible skb truesize change

[ Upstream commit 4672694bd4f1aebdab0ad763ae4716e89cb15221 ]

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 <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/net/ipv4/ip_fragment.c b/net/ipv4/ip_fragment.c
index df8fe0503de0e5050699be822ce04b383a677aa9..4cb1befc39494fcec05f6a93f949bb6eefc4e0a3 100644 (file)
--- a/net/ipv4/ip_fragment.c
+++ b/net/ipv4/ip_fragment.c
@@ -447,11 +447,16 @@ found:
                int i = end - FRAG_CB(next)->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);
                        FRAG_CB(next)->offset += i;
                        qp->q.meat -= i;
                        if (next->ip_summed != CHECKSUM_UNNECESSARY)