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Subject[patch 48/69] IPV6: Do no rely on skb->dst before it is assigned.
-stable review patch.  If anyone has any objections, please let us know.
---------------------

From: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>

Because skb->dst is assigned in ip6_route_input(), it is really
bad to use it in hop-by-hop option handler(s).

Closes: Bug #8450 (Eric Sesterhenn <snakebyte@gmx.de>)
Signed-off-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Chris Wright <chrisw@sous-sol.org>

---
net/ipv6/exthdrs.c | 16 ++++++++++++----
1 file changed, 12 insertions(+), 4 deletions(-)

--- linux-2.6.21.1.orig/net/ipv6/exthdrs.c
+++ linux-2.6.21.1/net/ipv6/exthdrs.c
@@ -652,6 +652,14 @@ EXPORT_SYMBOL_GPL(ipv6_invert_rthdr);
Hop-by-hop options.
**********************************/

+/*
+ * Note: we cannot rely on skb->dst before we assign it in ip6_route_input().
+ */
+static inline struct inet6_dev *ipv6_skb_idev(struct sk_buff *skb)
+{
+ return skb->dst ? ip6_dst_idev(skb->dst) : __in6_dev_get(skb->dev);
+}
+
/* Router Alert as of RFC 2711 */

static int ipv6_hop_ra(struct sk_buff **skbp, int optoff)
@@ -678,25 +686,25 @@ static int ipv6_hop_jumbo(struct sk_buff
if (skb->nh.raw[optoff+1] != 4 || (optoff&3) != 2) {
LIMIT_NETDEBUG(KERN_DEBUG "ipv6_hop_jumbo: wrong jumbo opt length/alignment %d\n",
skb->nh.raw[optoff+1]);
- IP6_INC_STATS_BH(ip6_dst_idev(skb->dst),
+ IP6_INC_STATS_BH(ipv6_skb_idev(skb),
IPSTATS_MIB_INHDRERRORS);
goto drop;
}

pkt_len = ntohl(*(__be32*)(skb->nh.raw+optoff+2));
if (pkt_len <= IPV6_MAXPLEN) {
- IP6_INC_STATS_BH(ip6_dst_idev(skb->dst), IPSTATS_MIB_INHDRERRORS);
+ IP6_INC_STATS_BH(ipv6_skb_idev(skb), IPSTATS_MIB_INHDRERRORS);
icmpv6_param_prob(skb, ICMPV6_HDR_FIELD, optoff+2);
return 0;
}
if (skb->nh.ipv6h->payload_len) {
- IP6_INC_STATS_BH(ip6_dst_idev(skb->dst), IPSTATS_MIB_INHDRERRORS);
+ IP6_INC_STATS_BH(ipv6_skb_idev(skb), IPSTATS_MIB_INHDRERRORS);
icmpv6_param_prob(skb, ICMPV6_HDR_FIELD, optoff);
return 0;
}

if (pkt_len > skb->len - sizeof(struct ipv6hdr)) {
- IP6_INC_STATS_BH(ip6_dst_idev(skb->dst), IPSTATS_MIB_INTRUNCATEDPKTS);
+ IP6_INC_STATS_BH(ipv6_skb_idev(skb), IPSTATS_MIB_INTRUNCATEDPKTS);
goto drop;
}

--
-
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