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xfrm6: Fix ICMPv6 and MH header checks in _decode_session6

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Ensure there's enough data left prior calling pskb_may_pull(). If
skb->data was already advanced, we'll call pskb_may_pull() with a
negative value converted to unsigned int -- leading to a huge
positive value. That won't matter in practice as pskb_may_pull()
will likely fail in this case, but it leads to underflow reports on
kernels handling such kind of over-/underflows, e.g. a PaX enabled
kernel instrumented with the size_overflow plugin.

Reported-by: satmd <satmd@lain.at>
Reported-and-tested-by: Marcin Jurkowski <marcin1j@gmail.com>
Signed-off-by: Mathias Krause <mathias.krause@secunet.com>
Cc: PaX Team <pageexec@freemail.hu>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
This commit is contained in:
Mathias Krause 2015-09-11 09:57:20 +02:00 committed by Steffen Klassert
parent 93efac3f2e
commit 04a6b8bfee
1 changed files with 4 additions and 2 deletions
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6
net/ipv6/xfrm6_policy.c
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@ -178,7 +178,8 @@ _decode_session6(struct sk_buff *skb, struct flowi *fl, int reverse)
return;
case IPPROTO_ICMPV6:
if (!onlyproto && pskb_may_pull(skb, nh + offset + 2 - skb->data)) {
if (!onlyproto && (nh + offset + 2 < skb->data ||
pskb_may_pull(skb, nh + offset + 2 - skb->data))) {
u8 *icmp;
nh = skb_network_header(skb);
@ -192,7 +193,8 @@ _decode_session6(struct sk_buff *skb, struct flowi *fl, int reverse)
#if IS_ENABLED(CONFIG_IPV6_MIP6)
case IPPROTO_MH:
offset += ipv6_optlen(exthdr);
if (!onlyproto && pskb_may_pull(skb, nh + offset + 3 - skb->data)) {
if (!onlyproto && (nh + offset + 3 < skb->data ||
pskb_may_pull(skb, nh + offset + 3 - skb->data))) {
struct ip6_mh *mh;
nh = skb_network_header(skb);