Component match callback function needs to check if expected data is
passed to it. 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.

Fixes: 7b882fe3e3e8b ("ALSA: hda - handle multiple i915 device instances")
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>
---
- Add "Fixes" tag
- Send to stable@vger.kernel.org

 sound/hda/hdac_i915.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/sound/hda/hdac_i915.c b/sound/hda/hdac_i915.c
index efe810af28c5..958b0975fa40 100644
--- a/sound/hda/hdac_i915.c
+++ b/sound/hda/hdac_i915.c
@@ -102,13 +102,13 @@ static int i915_component_master_match(struct device *dev, int subcomponent,
 	struct pci_dev *hdac_pci, *i915_pci;
 	struct hdac_bus *bus = data;
 
-	if (!dev_is_pci(dev))
+	if (!dev_is_pci(dev) || !bus)
 		return 0;
 
 	hdac_pci = to_pci_dev(bus->dev);
 	i915_pci = to_pci_dev(dev);
 
-	if (!strcmp(dev->driver->name, "i915") &&
+	if (dev->driver && !strcmp(dev->driver->name, "i915") &&
 	    subcomponent == I915_COMPONENT_AUDIO &&
 	    connectivity_check(i915_pci, hdac_pci))
 		return 1;
-- 
2.35.1.1021.g381101b075-goog

On Wed, 30 Mar 2022 23:19:13 +0200,
Won Chung wrote:
> 
> Component match callback function needs to check if expected data is
> passed to it. 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.
> 
> Fixes: 7b882fe3e3e8b ("ALSA: hda - handle multiple i915 device instances")
> 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>
> ---
> - Add "Fixes" tag
> - Send to stable@vger.kernel.org

You rather need to add "Cc: stable@vger.kernel.org" line to the patch
itself (around sign-off block), not actually Cc'ing the mail.
I edited manually, but please do it so at the next time.

Although I applied the patch as-is now, I wonder...


> -	if (!strcmp(dev->driver->name, "i915") &&
> +	if (dev->driver && !strcmp(dev->driver->name, "i915") &&

Can NULL dev->driver be really seen?  I thought the components are
added by the drivers, hence they ought to have the driver field set.
But there can be corner cases I overlooked.


thanks,

Takashi

On Thu, Mar 31, 2022 at 12:27 AM Takashi Iwai <tiwai@suse.de> wrote:
>
> On Wed, 30 Mar 2022 23:19:13 +0200,
> Won Chung wrote:
> >
> > Component match callback function needs to check if expected data is
> > passed to it. 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.
> >
> > Fixes: 7b882fe3e3e8b ("ALSA: hda - handle multiple i915 device instances")
> > 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>
> > ---
> > - Add "Fixes" tag
> > - Send to stable@vger.kernel.org
>
> You rather need to add "Cc: stable@vger.kernel.org" line to the patch
> itself (around sign-off block), not actually Cc'ing the mail.
> I edited manually, but please do it so at the next time.
>
> Although I applied the patch as-is now, I wonder...
>
>
> > -     if (!strcmp(dev->driver->name, "i915") &&
> > +     if (dev->driver && !strcmp(dev->driver->name, "i915") &&
>
> Can NULL dev->driver be really seen?  I thought the components are
> added by the drivers, hence they ought to have the driver field set.
> But there can be corner cases I overlooked.
>
>
> thanks,
>
> Takashi

Hi Takashi,

When I try using component_add in a different driver (usb4 in my
case), I think dev->driver here is NULL because the i915 drivers do
not have their component master fully bound when this new component is
registered. When I test it, it seems to be causing a crash.

Would it be okay for me to resend a new patch with the flags
corrected? I have mistakenly added Heikki and Mika as "Signed-off-by"
instead of "Suggested-by". I am sorry for that.

Thanks,
Won

On Thu, 31 Mar 2022 10:38:34 +0200,
Won Chung wrote:
> 
> On Thu, Mar 31, 2022 at 12:27 AM Takashi Iwai <tiwai@suse.de> wrote:
> >
> > On Wed, 30 Mar 2022 23:19:13 +0200,
> > Won Chung wrote:
> > >
> > > Component match callback function needs to check if expected data is
> > > passed to it. 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.
> > >
> > > Fixes: 7b882fe3e3e8b ("ALSA: hda - handle multiple i915 device instances")
> > > 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>
> > > ---
> > > - Add "Fixes" tag
> > > - Send to stable@vger.kernel.org
> >
> > You rather need to add "Cc: stable@vger.kernel.org" line to the patch
> > itself (around sign-off block), not actually Cc'ing the mail.
> > I edited manually, but please do it so at the next time.
> >
> > Although I applied the patch as-is now, I wonder...
> >
> >
> > > -     if (!strcmp(dev->driver->name, "i915") &&
> > > +     if (dev->driver && !strcmp(dev->driver->name, "i915") &&
> >
> > Can NULL dev->driver be really seen?  I thought the components are
> > added by the drivers, hence they ought to have the driver field set.
> > But there can be corner cases I overlooked.
> >
> >
> > thanks,
> >
> > Takashi
> 
> Hi Takashi,
> 
> When I try using component_add in a different driver (usb4 in my
> case), I think dev->driver here is NULL because the i915 drivers do
> not have their component master fully bound when this new component is
> registered. When I test it, it seems to be causing a crash.

Hm, from where component_add*() is called?  Basically dev->driver must
be already set before the corresponding driver gets bound at
__driver_probe_deviec().  So, if the device is added to component from
the corresponding driver's probe, dev->driver must be non-NULL.

> Would it be okay for me to resend a new patch with the flags
> corrected? I have mistakenly added Heikki and Mika as "Signed-off-by"
> instead of "Suggested-by". I am sorry for that.

Ah that's bad.  I'll reset the branch, then.  Please resubmit
properly.


thanks,

Takashi