* re: mlxsw: spectrum: PTP: Support timestamping on Spectrum-1 - potential null ptr dereference
@ 2019-07-02 15:01 Colin Ian King
2019-07-02 15:51 ` Petr Machata
0 siblings, 1 reply; 3+ messages in thread
From: Colin Ian King @ 2019-07-02 15:01 UTC (permalink / raw)
To: Petr Machata, Jiri Pirko, Ido Schimmel, David S. Miller, netdev,
linux-kernel
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 <petrm@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.
Colin
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: mlxsw: spectrum: PTP: Support timestamping on Spectrum-1 - potential null ptr dereference
2019-07-02 15:01 mlxsw: spectrum: PTP: Support timestamping on Spectrum-1 - potential null ptr dereference Colin Ian King
@ 2019-07-02 15:51 ` Petr Machata
2019-07-02 15:52 ` Colin Ian King
0 siblings, 1 reply; 3+ messages in thread
From: Petr Machata @ 2019-07-02 15:51 UTC (permalink / raw)
To: Colin Ian King
Cc: Jiri Pirko, Ido Schimmel, David S. Miller, netdev, linux-kernel
Colin Ian King <colin.king@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 <petrm@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.
Thanks for the report, I'll spin a fix!
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: mlxsw: spectrum: PTP: Support timestamping on Spectrum-1 - potential null ptr dereference
2019-07-02 15:51 ` Petr Machata
@ 2019-07-02 15:52 ` Colin Ian King
0 siblings, 0 replies; 3+ messages in thread
From: Colin Ian King @ 2019-07-02 15:52 UTC (permalink / raw)
To: Petr Machata
Cc: Jiri Pirko, Ido Schimmel, David S. Miller, netdev, linux-kernel
On 02/07/2019 16:51, Petr Machata wrote:
>
> Colin Ian King <colin.king@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 <petrm@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!
^ permalink raw reply [flat|nested] 3+ messages in thread
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