3.2-stable review patch.  If anyone has any objections, please let me know.

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

From: "David S. Miller" <davem@davemloft.net>

[ Upstream commit dccd9ecc374462e5d6a5b8f8110415a86c2213d8 ]

Due to RCU lookups and RCU based release, fib_info objects can
be found during lookup which have fi->fib_dead set.

We must ignore these entries, otherwise we risk dereferencing
the parts of the entry which are being torn down.

Reported-by: Yevgen Pronenko <redacted>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Ben Hutchings <redacted>
---
 net/ipv4/fib_trie.c |    2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/ipv4/fib_trie.c b/net/ipv4/fib_trie.c
index 3ce23f9..cd2d639 100644
--- a/net/ipv4/fib_trie.c
+++ b/net/ipv4/fib_trie.c

@@ -1372,6 +1372,8 @@ static int check_leaf(struct fib_table *tb, struct trie *t, struct leaf *l,
 
 			if (fa->fa_tos && fa->fa_tos != flp->flowi4_tos)
 				continue;
+			if (fi->fib_dead)
+				continue;
 			if (fa->fa_info->fib_scope < flp->flowi4_scope)
 				continue;
 			fib_alias_accessed(fa);