tree 9df83d2f2172866a59d72860f29ee24a94ba0b44
parent 13550ffc9515d234c43d79ef4a87328e88182baa
author Gao Feng <gfree.wind@vip.163.com> 1498625634 +0800
committer Greg Kroah-Hartman <gregkh@linuxfoundation.org> 1500615737 +0200

net: sched: Fix one possible panic when no destroy callback

commit c1a4872ebfb83b1af7144f7b29ac8c4b344a12a8 upstream.

When qdisc fail to init, qdisc_create would invoke the destroy callback
to cleanup. But there is no check if the callback exists really. So it
would cause the panic if there is no real destroy callback like the qdisc
codel, fq, and so on.

Take codel as an example following:
When a malicious user constructs one invalid netlink msg, it would cause
codel_init->codel_change->nla_parse_nested failed.
Then kernel would invoke the destroy callback directly but qdisc codel
doesn't define one. It causes one panic as a result.

Now add one the check for destroy to avoid the possible panic.

Fixes: 87b60cfacf9f ("net_sched: fix error recovery at qdisc creation")
Signed-off-by: Gao Feng <gfree.wind@vip.163.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>