net: neighbor: fix a crash caused by mod zero

pneigh_enqueue() tries to obtain a random delay by mod NEIGH_VAR(p, PROXY_DELAY). However, NEIGH_VAR(p, PROXY_DELAY) migth be zero at that point because someone could write zero to /proc/sys/net/ipv4/neigh/[device]/proxy_delay after the callers check it. This patch uses prandom_u32_max() to get a random delay instead which avoids potential division by zero. Signed-off-by: weichenchen <[email protected]> Signed-off-by: David S. Miller <[email protected]>
berg · Dec 28, 2020 · a533b70 · a533b70
1 parent 21fdca2
commit a533b70
Showing 1 changed file with 2 additions and 4 deletions.
diff --git a/net/core/neighbour.c b/net/core/neighbour.c
@@ -1569,10 +1569,8 @@ static void neigh_proxy_process(struct timer_list *t)
 void pneigh_enqueue(struct neigh_table *tbl, struct neigh_parms *p,
 		    struct sk_buff *skb)
 {
-	unsigned long now = jiffies;
-
-	unsigned long sched_next = now + (prandom_u32() %
-					  NEIGH_VAR(p, PROXY_DELAY));
+	unsigned long sched_next = jiffies +
+			prandom_u32_max(NEIGH_VAR(p, PROXY_DELAY));
 
 	if (tbl->proxy_queue.qlen > NEIGH_VAR(p, PROXY_QLEN)) {
 		kfree_skb(skb);