From a533b70a657c03137dd49cbcfee70aac086ab2b1 Mon Sep 17 00:00:00 2001
From: weichenchen <weichen.chen@linux.alibaba.com>
Date: Fri, 25 Dec 2020 13:44:45 +0800
Subject: [PATCH] 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 <weichen.chen@linux.alibaba.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
---
net/core/neighbour.c | 6 ++----
1 file changed, 2 insertions(+), 4 deletions(-)
diff --git a/net/core/neighbour.c b/net/core/neighbour.c
index 9500d28a43b0..277ed854aef1 100644
--- 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);
--
2.30.9