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From:   Won Chung <wonchung@google.com>
Date:   Wed, 30 Mar 2022 11:43:33 -0700
Message-ID: <CAOvb9yimjRJiX-RD8L_BUdpSWeZ+a76do=f-1-NDXC2Q2VjQ6g@mail.gmail.com>
Subject: Re: [PATCH] misc/mei: Add NULL check to component match callback functions
To:     Prashant Malani <pmalani@chromium.org>
Cc:     Tomas Winkler <tomas.winkler@intel.com>,
        Heikki Krogerus <heikki.krogerus@linux.intel.com>,
        Mika Westerberg <mika.westerberg@linux.intel.com>,
        Benson Leung <bleung@google.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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On Wed, Mar 30, 2022 at 11:18 AM Prashant Malani <pmalani@google.com> wrote:
>
> Hi Won,
>
> On Wed, 30 Mar 2022 at 10:58, Won Chung <wonchung@google.com> wrote:
>>
>> Component match callback functions need to check if expected data is
>> passed to them. Without this check, it can cause a NULL pointer
>> dereference when another driver registers a component before i915
>> drivers have their component master fully bind.
>>
> IMO this should have a "Fixes"  tag, and be picked back to stable branches.
> Also, please use my chromium.org account (pmalani@chromium.org) for upstream communications.
>
> Thanks!
>>
>> Signed-off-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
>> Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
>> Signed-off-by: Won Chung <wonchung@google.com>
>> ---
>>  drivers/misc/mei/hdcp/mei_hdcp.c | 2 +-
>>  drivers/misc/mei/pxp/mei_pxp.c   | 2 +-
>>  2 files changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/misc/mei/hdcp/mei_hdcp.c b/drivers/misc/mei/hdcp/mei_hdcp.c
>> index ec2a4fce8581..843dbc2b21b1 100644
>> --- a/drivers/misc/mei/hdcp/mei_hdcp.c
>> +++ b/drivers/misc/mei/hdcp/mei_hdcp.c
>> @@ -784,7 +784,7 @@ static int mei_hdcp_component_match(struct device *dev, int subcomponent,
>>  {
>>         struct device *base = data;
>>
>> -       if (strcmp(dev->driver->name, "i915") ||
>> +       if (!base || !dev->driver || strcmp(dev->driver->name, "i915") ||
>>             subcomponent != I915_COMPONENT_HDCP)
>>                 return 0;
>>
>> diff --git a/drivers/misc/mei/pxp/mei_pxp.c b/drivers/misc/mei/pxp/mei_pxp.c
>> index f7380d387bab..e32a81da8af6 100644
>> --- a/drivers/misc/mei/pxp/mei_pxp.c
>> +++ b/drivers/misc/mei/pxp/mei_pxp.c
>> @@ -131,7 +131,7 @@ static int mei_pxp_component_match(struct device *dev, int subcomponent,
>>  {
>>         struct device *base = data;
>>
>> -       if (strcmp(dev->driver->name, "i915") ||
>> +       if (!base || !dev->driver || strcmp(dev->driver->name, "i915") ||
>>             subcomponent != I915_COMPONENT_PXP)
>>                 return 0;
>>
>> --
>> 2.35.1.1021.g381101b075-goog
>>
>
>
> --
> -Prashant

Hi Prashant,

This currently does not fix a patch in the upstream, but is for a
future patch of adding component_add to usb4_port. Would we need the
"Fixes" tag for a future patch too?
Thinking again, I think it might be a better idea to have this as a
series of patches along with the patch to be sent after this one.

I changed the recipient email to send this to your chromium.org
account. Sorry for that.

Thanks,
Won