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ipv6: discard overlapping fragment 

RFC5722 prohibits reassembling fragments when some data overlaps.

Bug spotted by Zhang Zuotao <zuotao.zhang@6wind.com>.

Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Nicolas Dichtel 2010-09-03 05:13:05 +00:00 committed by David S. Miller
parent deabc772f3
commit 70789d7052
1 changed files with 15 additions and 56 deletions
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71
net/ipv6/reassembly.c
View File

@ -149,13 +149,6 @@ int ip6_frag_match(struct inet_frag_queue *q, void *a)
}
EXPORT_SYMBOL(ip6_frag_match);
/* Memory Tracking Functions. */
static void frag_kfree_skb(struct netns_frags *nf, struct sk_buff *skb)
{
atomic_sub(skb->truesize, &nf->mem);
kfree_skb(skb);
}
void ip6_frag_init(struct inet_frag_queue *q, void *a)
{
struct frag_queue *fq = container_of(q, struct frag_queue, q);
@ -346,58 +339,22 @@ static int ip6_frag_queue(struct frag_queue *fq, struct sk_buff *skb,
}
found:
/* We found where to put this one. Check for overlap with
* preceding fragment, and, if needed, align things so that
* any overlaps are eliminated.
/* RFC5722, Section 4:
* 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, including those not yet received) MUST be silently
* discarded.
*/
if (prev) {
int i = (FRAG6_CB(prev)->offset + prev->len) - offset;
if (i > 0) {
offset += i;
if (end <= offset)
goto err;
if (!pskb_pull(skb, i))
goto err;
if (skb->ip_summed != CHECKSUM_UNNECESSARY)
skb->ip_summed = CHECKSUM_NONE;
}
}
/* Check for overlap with preceding fragment. */
if (prev &&
(FRAG6_CB(prev)->offset + prev->len) - offset > 0)
goto discard_fq;
/* Look for overlap with succeeding segments.
* If we can merge fragments, do it.
*/
while (next && FRAG6_CB(next)->offset < end) {
int i = end - FRAG6_CB(next)->offset; /* overlap is 'i' bytes */
if (i < next->len) {
/* Eat head of the next overlapped fragment
* and leave the loop. The next ones cannot overlap.
*/
if (!pskb_pull(next, i))
goto err;
FRAG6_CB(next)->offset += i; /* next fragment */
fq->q.meat -= i;
if (next->ip_summed != CHECKSUM_UNNECESSARY)
next->ip_summed = CHECKSUM_NONE;
break;
} else {
struct sk_buff *free_it = next;
/* Old fragment is completely overridden with
* new one drop it.
*/
next = next->next;
if (prev)
prev->next = next;
else
fq->q.fragments = next;
fq->q.meat -= free_it->len;
frag_kfree_skb(fq->q.net, free_it);
}
}
/* Look for overlap with succeeding segment. */
if (next && FRAG6_CB(next)->offset < end)
goto discard_fq;
FRAG6_CB(skb)->offset = offset;
@ -436,6 +393,8 @@ found:
write_unlock(&ip6_frags.lock);
return -1;
discard_fq:
fq_kill(fq);
err:
IP6_INC_STATS(net, ip6_dst_idev(skb_dst(skb)),
IPSTATS_MIB_REASMFAILS);