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xfrm4: Fix uninitialized memory read in _decode_session4

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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: 1da177e4c3 ("Linux-2.6.12-rc2")
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
This commit is contained in:
Steffen Klassert 2019-02-26 07:04:50 +01:00
parent 025c65e119
commit 8742dc86d0
1 changed files with 13 additions and 11 deletions
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24
net/ipv4/xfrm4_policy.c
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@ -111,7 +111,8 @@ static void
_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 @@ _decode_session4(struct sk_buff *skb, struct flowi *fl, int reverse)
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 @@ _decode_session4(struct sk_buff *skb, struct flowi *fl, int reverse)
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 @@ _decode_session4(struct sk_buff *skb, struct flowi *fl, int reverse)
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 @@ _decode_session4(struct sk_buff *skb, struct flowi *fl, int reverse)
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 @@ _decode_session4(struct sk_buff *skb, struct flowi *fl, int reverse)
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 @@ _decode_session4(struct sk_buff *skb, struct flowi *fl, int reverse)
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 @@ _decode_session4(struct sk_buff *skb, struct flowi *fl, int reverse)
__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 @@ _decode_session4(struct sk_buff *skb, struct flowi *fl, int reverse)
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,