xfrm4: Fix uninitialized memory read in _decode_session4
We currently don't reload pointers pointing into skb header
after doing pskb_may_pull() in _decode_session4(). So in case
pskb_may_pull() changed the pointers, we read from random
memory. Fix this by putting all the needed infos on the
stack, so that we don't need to access the header pointers
after doing pskb_may_pull().
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
diff --git a/net/ipv4/xfrm4_policy.c b/net/ipv4/xfrm4_policy.c
index d73a6d6..2b144b9 100644
--- a/net/ipv4/xfrm4_policy.c
+++ b/net/ipv4/xfrm4_policy.c
@@ -111,7 +111,8 @@
_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;
+ int ihl = iph->ihl;
+ u8 *xprth = skb_network_header(skb) + ihl * 4;
struct flowi4 *fl4 = &fl->u.ip4;
int oif = 0;
@@ -122,6 +123,11 @@
fl4->flowi4_mark = skb->mark;
fl4->flowi4_oif = reverse ? skb->skb_iif : oif;
+ fl4->flowi4_proto = iph->protocol;
+ fl4->daddr = reverse ? iph->saddr : iph->daddr;
+ fl4->saddr = reverse ? iph->daddr : iph->saddr;
+ fl4->flowi4_tos = iph->tos;
+
if (!ip_is_fragment(iph)) {
switch (iph->protocol) {
case IPPROTO_UDP:
@@ -133,7 +139,7 @@
pskb_may_pull(skb, xprth + 4 - skb->data)) {
__be16 *ports;
- xprth = skb_network_header(skb) + iph->ihl * 4;
+ xprth = skb_network_header(skb) + ihl * 4;
ports = (__be16 *)xprth;
fl4->fl4_sport = ports[!!reverse];
@@ -146,7 +152,7 @@
pskb_may_pull(skb, xprth + 2 - skb->data)) {
u8 *icmp;
- xprth = skb_network_header(skb) + iph->ihl * 4;
+ xprth = skb_network_header(skb) + ihl * 4;
icmp = xprth;
fl4->fl4_icmp_type = icmp[0];
@@ -159,7 +165,7 @@
pskb_may_pull(skb, xprth + 4 - skb->data)) {
__be32 *ehdr;
- xprth = skb_network_header(skb) + iph->ihl * 4;
+ xprth = skb_network_header(skb) + ihl * 4;
ehdr = (__be32 *)xprth;
fl4->fl4_ipsec_spi = ehdr[0];
@@ -171,7 +177,7 @@
pskb_may_pull(skb, xprth + 8 - skb->data)) {
__be32 *ah_hdr;
- xprth = skb_network_header(skb) + iph->ihl * 4;
+ xprth = skb_network_header(skb) + ihl * 4;
ah_hdr = (__be32 *)xprth;
fl4->fl4_ipsec_spi = ah_hdr[1];
@@ -183,7 +189,7 @@
pskb_may_pull(skb, xprth + 4 - skb->data)) {
__be16 *ipcomp_hdr;
- xprth = skb_network_header(skb) + iph->ihl * 4;
+ xprth = skb_network_header(skb) + ihl * 4;
ipcomp_hdr = (__be16 *)xprth;
fl4->fl4_ipsec_spi = htonl(ntohs(ipcomp_hdr[1]));
@@ -196,7 +202,7 @@
__be16 *greflags;
__be32 *gre_hdr;
- xprth = skb_network_header(skb) + iph->ihl * 4;
+ xprth = skb_network_header(skb) + ihl * 4;
greflags = (__be16 *)xprth;
gre_hdr = (__be32 *)xprth;
@@ -213,10 +219,6 @@
break;
}
}
- fl4->flowi4_proto = iph->protocol;
- fl4->daddr = reverse ? iph->saddr : iph->daddr;
- fl4->saddr = reverse ? iph->daddr : iph->saddr;
- fl4->flowi4_tos = iph->tos;
}
static void xfrm4_update_pmtu(struct dst_entry *dst, struct sock *sk,
