Re: [PATCH] net: sched: sch_teql: fix null-pointer dereference

[Pavel Tikhomirov]

On 4/8/21 6:26 PM, Eric Dumazet wrote:
> On 4/8/21 5:14 PM, Pavel Tikhomirov wrote:
> > Reproduce:
> >
> >    modprobe sch_teql
> >    tc qdisc add dev teql0 root teql0
> >
> > This leads to (for instance in Centos 7 VM) OOPS:
> >
> >
> >
> > Null pointer dereference happens on master->slaves dereference in
> > teql_destroy() as master is null-pointer.
> >
> > When qdisc_create() calls teql_qdisc_init() it imediately fails after
> > check "if (m->dev == dev)" because both devices are teql0, and it does
> > not set qdisc_priv(sch)->m leaving it zero on error path, then
> > qdisc_create() imediately calls teql_destroy() which does not expect
> > zero master pointer and we get OOPS.
> >
> > Signed-off-by: Pavel Tikhomirov <ptikhomirov@xxxxxxxxxxxxx>
> > ---
>
> This makes sense, thanks !
>
> Reviewed-by: Eric Dumazet <edumazet@xxxxxxxxxx>

Thanks!

> I would think bug origin is
>
> Fixes: 87b60cfacf9f ("net_sched: fix error recovery at qdisc creation")
>
> Can you confirm you have this backported to 3.10.0-1062.7.1.el7.x86_64 ?

According to our source copy it looks backported to 1062.7.1, please see:
https://src.openvz.org/projects/OVZ/repos/vzkernel/browse/net/sched/sch_api.c?at=refs%2Ftags%2Frh7-3.10.0-1062.7.1.el7#1167

--
Best regards, Tikhomirov Pavel
Software Developer, Virtuozzo.