[32/38] ipv6: fix NULL dereference in udp6_ufo_fragment()

[Greg KH]

3.0-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Jason Wang <jasowang@xxxxxxxxxx>

This patch fixes the issue caused by ef81bb40bf15f350fe865f31fa42f1082772a576
which is a backport of upstream 87c48fa3b4630905f98268dde838ee43626a060c. The
problem does not exist in upstream.

We do not check whether route is attached before trying to assign ip
identification through route dest which lead NULL pointer dereference. This
happens when host bridge transmit a packet from guest.

This patch changes ipv6_select_ident() to accept in6_addr as its paramter and
fix the issue by using the destination address in ipv6 header when no route is
attached.

Signed-off-by: Jason Wang <jasowang@xxxxxxxxxx>
Acked-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>
---
 include/net/ipv6.h    |    2 +-
 net/ipv6/ip6_output.c |   10 +++++-----
 net/ipv6/udp.c        |    4 +++-
 3 files changed, 9 insertions(+), 7 deletions(-)

--- a/include/net/ipv6.h
+++ b/include/net/ipv6.h
@@ -463,7 +463,7 @@ static inline int ipv6_addr_diff(const s
 	return __ipv6_addr_diff(a1, a2, sizeof(struct in6_addr));
 }
 
-extern void ipv6_select_ident(struct frag_hdr *fhdr, struct rt6_info *rt);
+extern void ipv6_select_ident(struct frag_hdr *fhdr, struct in6_addr *addr);
 
 /*
  *	Prototypes exported by ipv6
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -620,9 +620,9 @@ static u32 __ipv6_select_ident(const str
 	return hash + newid;
 }
 
-void ipv6_select_ident(struct frag_hdr *fhdr, struct rt6_info *rt)
+void ipv6_select_ident(struct frag_hdr *fhdr, struct in6_addr *addr)
 {
-	fhdr->identification = htonl(__ipv6_select_ident(&rt->rt6i_dst.addr));
+	fhdr->identification = htonl(__ipv6_select_ident(addr));
 }
 
 int ip6_fragment(struct sk_buff *skb, int (*output)(struct sk_buff *))
@@ -709,7 +709,7 @@ int ip6_fragment(struct sk_buff *skb, in
 		skb_reset_network_header(skb);
 		memcpy(skb_network_header(skb), tmp_hdr, hlen);
 
-		ipv6_select_ident(fh, rt);
+		ipv6_select_ident(fh, &rt->rt6i_dst.addr);
 		fh->nexthdr = nexthdr;
 		fh->reserved = 0;
 		fh->frag_off = htons(IP6_MF);
@@ -855,7 +855,7 @@ slow_path:
 		fh->nexthdr = nexthdr;
 		fh->reserved = 0;
 		if (!frag_id) {
-			ipv6_select_ident(fh, rt);
+			ipv6_select_ident(fh, &rt->rt6i_dst.addr);
 			frag_id = fh->identification;
 		} else
 			fh->identification = frag_id;
@@ -1146,7 +1146,7 @@ static inline int ip6_ufo_append_data(st
 		skb_shinfo(skb)->gso_size = (mtu - fragheaderlen -
 					     sizeof(struct frag_hdr)) & ~7;
 		skb_shinfo(skb)->gso_type = SKB_GSO_UDP;
-		ipv6_select_ident(&fhdr, rt);
+		ipv6_select_ident(&fhdr, &rt->rt6i_dst.addr);
 		skb_shinfo(skb)->ip6_frag_id = fhdr.identification;
 		__skb_queue_tail(&sk->sk_write_queue, skb);
 
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -1309,6 +1309,7 @@ static struct sk_buff *udp6_ufo_fragment
 	u8 frag_hdr_sz = sizeof(struct frag_hdr);
 	int offset;
 	__wsum csum;
+	struct rt6_info *rt = (struct rt6_info *)skb_dst(skb);
 
 	mss = skb_shinfo(skb)->gso_size;
 	if (unlikely(skb->len <= mss))
@@ -1359,7 +1360,8 @@ static struct sk_buff *udp6_ufo_fragment
 	fptr = (struct frag_hdr *)(skb_network_header(skb) + unfrag_ip6hlen);
 	fptr->nexthdr = nexthdr;
 	fptr->reserved = 0;
-	ipv6_select_ident(fptr, (struct rt6_info *)skb_dst(skb));
+	ipv6_select_ident(fptr,
+			  rt ? &rt->rt6i_dst.addr : &ipv6_hdr(skb)->daddr);
 
 	/* Fragment the skb. ipv6 header and the remaining fields of the
 	 * fragment header are updated in ipv6_gso_segment()


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