[PATCH AUTOSEL 4.19 43/43] sch_netem: fix a divide by zero in tabledist()

Sasha Levin
2019-10-01T16:50:34Z

From: Eric Dumazet <edumazet@google.com>

[ Upstream commit b41d936b5ecfdb3a4abc525ce6402a6c49cffddc ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/sched/sch_netem.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/sched/sch_netem.c b/net/sched/sch_netem.c
index 4dfe10b9f96c8..86350fe5cfc8f 100644
--- a/net/sched/sch_netem.c
+++ b/net/sched/sch_netem.c
@@ -749,7 +749,7 @@ 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);
--
2.20.1