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xfrm: Fix null pointer dereference when decoding sessions 

On some codepaths the skb does not have a dst entry
when xfrm_decode_session() is called. So check for
a valid skb_dst() before dereferencing the device
interface index. We use 0 as the device index if
there is no valid skb_dst(), or at reverse decoding
we use skb_iif as device interface index.

Bug was introduced with git commit bafd4bd4dc
("xfrm: Decode sessions with output interface.").

Reported-by: Meelis Roos <mroos@linux.ee>
Tested-by: Meelis Roos <mroos@linux.ee>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
This commit is contained in:
Steffen Klassert 2013-10-30 11:16:28 +01:00
parent eeb1b73378
commit 84502b5ef9
2 changed files with 10 additions and 2 deletions
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6
net/ipv4/xfrm4_policy.c
View File

@ -104,10 +104,14 @@ _decode_session4(struct sk_buff *skb, struct flowi *fl, int reverse)
const struct iphdr *iph = ip_hdr(skb);
u8 *xprth = skb_network_header(skb) + iph->ihl * 4;
struct flowi4 *fl4 = &fl->u.ip4;
int oif = 0;
if (skb_dst(skb))
oif = skb_dst(skb)->dev->ifindex;
memset(fl4, 0, sizeof(struct flowi4));
fl4->flowi4_mark = skb->mark;
fl4->flowi4_oif = skb_dst(skb)->dev->ifindex;
fl4->flowi4_oif = reverse ? skb->skb_iif : oif;
if (!ip_is_fragment(iph)) {
switch (iph->protocol) {

6
net/ipv6/xfrm6_policy.c
View File

@ -135,10 +135,14 @@ _decode_session6(struct sk_buff *skb, struct flowi *fl, int reverse)
struct ipv6_opt_hdr *exthdr;
const unsigned char *nh = skb_network_header(skb);
u8 nexthdr = nh[IP6CB(skb)->nhoff];
int oif = 0;
if (skb_dst(skb))
oif = skb_dst(skb)->dev->ifindex;
memset(fl6, 0, sizeof(struct flowi6));
fl6->flowi6_mark = skb->mark;
fl6->flowi6_oif = skb_dst(skb)->dev->ifindex;
fl6->flowi6_oif = reverse ? skb->skb_iif : oif;
fl6->daddr = reverse ? hdr->saddr : hdr->daddr;
fl6->saddr = reverse ? hdr->daddr : hdr->saddr;