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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>
This commit is contained in:
Alexander Duyck 2015-03-10 14:39:34 -07:00 committed by David S. Miller
parent 416377ea39
commit ddb4b9a132
1 changed files with 2 additions and 4 deletions
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6
net/ipv4/fib_trie.c
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@ -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);
}