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xfrm4: Fix uninitialized memory read in _decode_session4

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[ Upstream commit 8742dc86d0 ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Steffen Klassert
2019-02-26 07:04:50 +01:00
committed by Chris
parent 67046f936d
commit ec23e7cfc0
1 changed files with 13 additions and 11 deletions
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24
net/ipv4/xfrm4_policy.c
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@@ -112,7 +112,8 @@ 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;
@@ -123,6 +124,11 @@ _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:
@@ -134,7 +140,7 @@ _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];
@@ -147,7 +153,7 @@ _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];
@@ -160,7 +166,7 @@ _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];
@@ -172,7 +178,7 @@ _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];
@@ -184,7 +190,7 @@ _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]));
@@ -197,7 +203,7 @@ _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;
@@ -214,10 +220,6 @@ _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 inline int xfrm4_garbage_collect(struct dst_ops *ops)