fib_trie: Address possible NULL pointer dereference in resize

If the inflate call failed it would return NULL.  As a result tp would be
set to NULL and cause use to trigger a NULL pointer dereference in
should_halve if the inflate failed on the first attempt.

In order to prevent this we should decrement max_work before we actually
attempt to inflate as this will force us to exit before attempting to halve
a node we should have inflated.  In order to keep things symmetric between
inflate and halve I went ahead and also moved the decrement of max_work for
the halve case as well so we take care of that before we actually attempt
to halve the tnode.

Fixes: 88bae714 ("fib_trie: Add key vector to root, return parent key_vector in resize")
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Alexander Duyck <alexander.h.duyck@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv4/fib_trie.c b/net/ipv4/fib_trie.c
index 44cab1d41463ce732da3b033ec8e29a373ff4306..83290beaf7cf8c3eafe3e3e29b04a821f3a1e90f 100644 (file)
--- a/net/ipv4/fib_trie.c
+++ b/net/ipv4/fib_trie.c
@@ -830,7 +830,7 @@ static struct key_vector *resize(struct trie *t, struct key_vector *tn)
        /* Double as long as the resulting node has a number of
         * nonempty nodes that are above the threshold.
         */
-       while (should_inflate(tp, tn) && max_work) {
+       while (should_inflate(tp, tn) && max_work--) {
                tp = inflate(t, tn);
                if (!tp) {
 #ifdef CONFIG_IP_FIB_TRIE_STATS
@@ -839,7 +839,6 @@ static struct key_vector *resize(struct trie *t, struct key_vector *tn)
                        break;
                }
 
-               max_work--;
                tn = get_child(tp, cindex);
        }
 
@@ -850,7 +849,7 @@ static struct key_vector *resize(struct trie *t, struct key_vector *tn)
        /* Halve as long as the number of empty children in this
         * node is above threshold.
         */
-       while (should_halve(tp, tn) && max_work) {
+       while (should_halve(tp, tn) && max_work--) {
                tp = halve(t, tn);
                if (!tp) {
 #ifdef CONFIG_IP_FIB_TRIE_STATS
@@ -859,7 +858,6 @@ static struct key_vector *resize(struct trie *t, struct key_vector *tn)
                        break;
                }
 
-               max_work--;
                tn = get_child(tp, cindex);
        }