[PATCH 3.16 38/72] sch_netem: fix a divide by zero in tabledist()

Ben Hutchings
2019-12-08T13:57:40Z

From: Eric Dumazet <edumazet@google.com>

commit b41d936b5ecfdb3a4abc525ce6402a6c49cffddc upstream.

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: Ben Hutchings <ben@decadent.org.uk>
---
net/sched/sch_netem.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/net/sched/sch_netem.c
+++ b/net/sched/sch_netem.c
@@ -737,7 +737,7 @@ static int get_dist_table(struct Qdisc *
int i;
size_t s;

- if (n > NETEM_DIST_MAX)
+ if (!n || n > NETEM_DIST_MAX)
return -EINVAL;

s = sizeof(struct disttable) + n * sizeof(s16);