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mpls: In mpls_egress verify the packet length. 

Reobert Shearman noticed that mpls_egress is failing to verify that
the bytes to be examined are in fact present in the packet before
mpls_egress reads those bytes.

As suggested by David Miller reduce this to a single pskb_may_pull
call so that we don't do unnecessary work in the fast path.

Reported-by: Robert Shearman <rshearma@brocade.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric W. Biederman 2015-03-12 18:22:59 -05:00 committed by David S. Miller
parent 2c29b2354a
commit 76fecd8275
1 changed files with 16 additions and 1 deletions
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17
net/mpls/af_mpls.c
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@ -92,9 +92,24 @@ static bool mpls_egress(struct mpls_route *rt, struct sk_buff *skb,
* The strange cases if we choose to support them will require
* manual configuration.
*/
struct iphdr *hdr4 = ip_hdr(skb);
struct iphdr *hdr4;
bool success = true;
/* The IPv4 code below accesses through the IPv4 header
* checksum, which is 12 bytes into the packet.
* The IPv6 code below accesses through the IPv6 hop limit
* which is 8 bytes into the packet.
*
* For all supported cases there should always be at least 12
* bytes of packet data present. The IPv4 header is 20 bytes
* without options and the IPv6 header is always 40 bytes
* long.
*/
if (!pskb_may_pull(skb, 12))
return false;
/* Use ip_hdr to find the ip protocol version */
hdr4 = ip_hdr(skb);
if (hdr4->version == 4) {
skb->protocol = htons(ETH_P_IP);
csum_replace2(&hdr4->check,