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SubjectRe: [PATCH] net: sched: sch_teql: fix null-pointer dereference
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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@virtuozzo.com>
>> ---
>
> This makes sense, thanks !
>
> Reviewed-by: Eric Dumazet <edumazet@google.com>

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.

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