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

[Eric Dumazet]

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>

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 ?