[PATCH 4.2 013/124] fib_trie: leaf_walk_rcu should not compute key if key is less than pn->key

[Greg Kroah-Hartman]

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

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

From: Alexander Duyck <aduyck@xxxxxxxxxxxx>

[ Upstream commit c2229fe1430d4e1c70e36520229dd64a87802b20 ]

We were computing the child index in cases where the key value we were
looking for was actually less than the base key of the tnode.  As a result
we were getting incorrect index values that would cause us to skip over
some children.

To fix this I have added a test that will force us to use child index 0 if
the key we are looking for is less than the key of the current tnode.

Fixes: 8be33e955cb9 ("fib_trie: Fib walk rcu should take a tnode and key instead of a trie and a leaf")
Reported-by: Brian Rak <brak@xxxxxxxxxxxxxxx>
Signed-off-by: Alexander Duyck <aduyck@xxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 net/ipv4/fib_trie.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/net/ipv4/fib_trie.c
+++ b/net/ipv4/fib_trie.c
@@ -1561,7 +1561,7 @@ static struct key_vector *leaf_walk_rcu(
 	do {
 		/* record parent and next child index */
 		pn = n;
-		cindex = key ? get_index(key, pn) : 0;
+		cindex = (key > pn->key) ? get_index(key, pn) : 0;
 
 		if (cindex >> pn->bits)
 			break;


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