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Date: Fri, 18 Dec 2020 12:20:19 +0800 From: weichenchen <weichen.chen@...ux.alibaba.com> To: davem@...emloft.net, kuba@...nel.org Cc: liuhangbin@...il.com, dsahern@...nel.org, jdike@...mai.com, mrv@...atatu.com, lirongqing@...du.com, nikolay@...ulusnetworks.com, roopa@...ulusnetworks.com, netdev@...r.kernel.org, linux-kernel@...r.kernel.org, splendidsky.cwc@...baba-inc.com, yanxu.zw@...baba-inc.com, weichenchen <weichen.chen@...ux.alibaba.com> 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 double-checks NEIGH_VAR(p, PROXY_DELAY) in pneigh_enqueue() to ensure not to take zero as modulus. Signed-off-by: weichenchen <weichen.chen@...ux.alibaba.com> --- net/core/neighbour.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/net/core/neighbour.c b/net/core/neighbour.c index 9500d28a43b0..eb5d015c53d3 100644 --- a/net/core/neighbour.c +++ b/net/core/neighbour.c @@ -1570,9 +1570,14 @@ void pneigh_enqueue(struct neigh_table *tbl, struct neigh_parms *p, struct sk_buff *skb) { unsigned long now = jiffies; + unsigned long sched_next; - unsigned long sched_next = now + (prandom_u32() % - NEIGH_VAR(p, PROXY_DELAY)); + int delay = NEIGH_VAR(p, PROXY_DELAY); + + if (delay <= 0) + sched_next = now; + else + sched_next = now + (prandom_u32() % delay); if (tbl->proxy_queue.qlen > NEIGH_VAR(p, PROXY_QLEN)) { kfree_skb(skb); -- 2.20.1 (Apple Git-117)
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