From: Eric Dumazet <edumazet@google.com>
Date: Wed, 18 Sep 2019 15:05:39 +0000 (-0700)
Subject: sch_netem: fix a divide by zero in tabledist()
X-Git-Tag: v5.4-rc1~14^2~75
X-Git-Url: https://asedeno.scripts.mit.edu/gitweb/?a=commitdiff_plain;h=b41d936b5ecfdb3a4abc525ce6402a6c49cffddc;p=linux.git

sch_netem: fix a divide by zero in tabledist()

syzbot managed to crash the kernel in tabledist() loading
an empty distribution table.

	t = dist->table[rnd % dist->size];

Simply return an error when such load is attempted.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: syzbot <syzkaller@googlegroups.com>
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
---

diff --git a/net/sched/sch_netem.c b/net/sched/sch_netem.c
index b17f2ed970e2..f5cb35e550f8 100644
--- a/net/sched/sch_netem.c
+++ b/net/sched/sch_netem.c
@@ -777,7 +777,7 @@ static int get_dist_table(struct Qdisc *sch, struct disttable **tbl,
 	struct disttable *d;
 	int i;
 
-	if (n > NETEM_DIST_MAX)
+	if (!n || n > NETEM_DIST_MAX)
 		return -EINVAL;
 
 	d = kvmalloc(sizeof(struct disttable) + n * sizeof(s16), GFP_KERNEL);