Patch "ipv6: Check rt->dst.from for the DST_NOCACHE route" has been added to the 4.2-stable tree

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    ipv6: Check rt->dst.from for the DST_NOCACHE route

to the 4.2-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     ipv6-check-rt-dst.from-for-the-dst_nocache-route.patch
and it can be found in the queue-4.2 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From foo@baz Fri Dec 11 11:38:35 EST 2015
From: Martin KaFai Lau <kafai@fb.com>
Date: Wed, 11 Nov 2015 11:51:08 -0800
Subject: ipv6: Check rt->dst.from for the DST_NOCACHE route

From: Martin KaFai Lau <kafai@fb.com>

[ Upstrem commit 02bcf4e082e4dc634409a6a6cb7def8806d6e5e6 ]

All DST_NOCACHE rt6_info used to have rt->dst.from set to
its parent.

After commit 8e3d5be73681 ("ipv6: Avoid double dst_free"),
DST_NOCACHE is also set to rt6_info which does not have
a parent (i.e. rt->dst.from is NULL).

This patch catches the rt->dst.from == NULL case.

Fixes: 8e3d5be73681 ("ipv6: Avoid double dst_free")
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Cc: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 include/net/ip6_fib.h |    3 ++-
 net/ipv6/route.c      |    3 ++-
 2 files changed, 4 insertions(+), 2 deletions(-)

--- a/include/net/ip6_fib.h
+++ b/include/net/ip6_fib.h
@@ -165,7 +165,8 @@ static inline void rt6_update_expires(st
 
 static inline u32 rt6_get_cookie(const struct rt6_info *rt)
 {
-	if (rt->rt6i_flags & RTF_PCPU || unlikely(rt->dst.flags & DST_NOCACHE))
+	if (rt->rt6i_flags & RTF_PCPU ||
+	    (unlikely(rt->dst.flags & DST_NOCACHE) && rt->dst.from))
 		rt = (struct rt6_info *)(rt->dst.from);
 
 	return rt->rt6i_node ? rt->rt6i_node->fn_sernum : 0;
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -1284,7 +1284,8 @@ static struct dst_entry *ip6_dst_check(s
 
 	rt6_dst_from_metrics_check(rt);
 
-	if ((rt->rt6i_flags & RTF_PCPU) || unlikely(dst->flags & DST_NOCACHE))
+	if (rt->rt6i_flags & RTF_PCPU ||
+	    (unlikely(dst->flags & DST_NOCACHE) && rt->dst.from))
 		return rt6_dst_from_check(rt, cookie);
 	else
 		return rt6_check(rt, cookie);


Patches currently in stable-queue which might be from kafai@fb.com are

queue-4.2/ipv6-check-rt-dst.from-for-the-dst_nocache-route.patch
queue-4.2/ipv6-avoid-creating-rtf_cache-from-a-rt-that-is-not-managed-by-fib6-tree.patch
queue-4.2/ipv6-check-expire-on-dst_nocache-route.patch