Re: [net PATCH] net: sched: Fix one possible panic when no destroy callback

On Tue, 2017-06-27 at 10:08 -0700, Cong Wang wrote:

On Tue, Jun 27, 2017 at 9:50 AM, Eric Dumazet [off-list ref] wrote:

quoted

On Tue, 2017-06-27 at 09:30 -0700, Cong Wang wrote:

quoted

On Mon, Jun 26, 2017 at 6:35 PM,  [off-list ref] wrote:

quoted

From: Gao Feng <redacted>

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 these
qdisc codel, pfifo, pfifo_fast, and so on.

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

Signed-off-by: Gao Feng <redacted>

Looks good,

Acked-by: Cong Wang <redacted>

This is introduced by commit 87b60cfacf9f17cf71933c6e33b.
Please add proper Fixes tag next time.

Given that pfifo, pfifo_fast or codel can not fail their init,

How about codel_init() -> codel_change() -> nla_parse_nested() ?

Yeah, with a malicious user space then (iproute2/tc is fine), codel
could be problematic.

pfifo and pfifo_fast can definitely not hit this bug.

changelog needs a bit of attention, even if the bug is real.

Thanks.