On 02/07/2019 16:51, Petr Machata wrote:
>
> Colin Ian King <colin.k...@canonical.com> writes:
>
>> Hi,
>>
>> Static analysis with Coverity on today's linux-next has found a
>> potential null pointer dereference bug with the following commit:
>>
>> commit d92e4e6e33c8b19635be70fb8935b627d2e4f8fe
>> Author: Petr Machata <pe...@mellanox.com>
>> Date: Sun Jun 30 09:04:56 2019 +0300
>>
>> mlxsw: spectrum: PTP: Support timestamping on Spectrum-1
>>
>>
>> In function: mlxsw_sp1_ptp_packet_finish the offending code is as follows:
>>
>> /* Between capturing the packet and finishing it, there is a
>> window of
>> * opportunity for the originating port to go away (e.g. due to a
>> * split). Also make sure the SKB device reference is still valid.
>> */
>> mlxsw_sp_port = mlxsw_sp->ports[local_port];
>> if (!mlxsw_sp_port && (!skb->dev || skb->dev == mlxsw_sp_port->dev)) {
>> dev_kfree_skb_any(skb);
>> return;
>> }
>>
>> If mlxsw_sp_port is null and skb->dev is not-null then the comparison
>> "skb->dev == mlxsw_sp_port->dev" ends up with a null pointer dereference.
>>
>> I think the if statement should be:
>>
>> if (mlxsw_sp_port && (!skb->dev || skb->dev == mlxsw_sp_port->dev))
>>
>> ..but I'm not 100% sure as I may be missing something a bit more subtle
>> here.
>
> Yes, that line is wrong. It's missing a pair of parens, it should be:
>
> if (!(mlxsw_sp_port && (!skb->dev || skb->dev ==
> mlxsw_sp_port->dev))) {
>
> I.e. I need a port && I need the skb->dev to still refer to that port
> (or else be NULL). If that doesn't hold, bail out.
Ah, that makes sense.
>
> Thanks for the report, I'll spin a fix!
>
OK, thanks!
