[PATCH AUTOSEL 5.2 62/63] sch_netem: fix a divide by zero in tabledist()

[Sasha Levin]

From: Eric Dumazet <eduma...@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 <eduma...@google.com>
Reported-by: syzbot <syzkal...@googlegroups.com>
Signed-off-by: Jakub Kicinski <jakub.kicin...@netronome.com>
Signed-off-by: Sasha Levin <sas...@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 b17f2ed970e29..f5cb35e550f8d 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);
-- 
2.20.1