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net: neighbor: fix a crash caused by mod zero

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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>
This commit is contained in:
weichenchen 2020-12-25 13:44:45 +08:00 committed by David S. Miller
parent 21fdca22eb
commit a533b70a65
1 changed files with 2 additions and 4 deletions
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6
net/core/neighbour.c
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@ -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);