sch_netem: fix a divide by zero in tabledist()

[ 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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/net/sched/sch_netem.c b/net/sched/sch_netem.c
index e9812e21dbc9b99b573cc8339201e7caec0e232b..12e3ae09c4ba119fcac57c8171c83e4417f5f2e9 100644 (file)
--- a/net/sched/sch_netem.c
+++ b/net/sched/sch_netem.c
@@ -711,7 +711,7 @@ static int get_dist_table(struct Qdisc *sch, const struct nlattr *attr)
        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);