linux-kernel - Re: [PATCH v2] sound/hda: Add NULL check to component match callback function

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Date:   Thu, 31 Mar 2022 09:27:35 +0200
From:   Takashi Iwai <tiwai@...e.de>
To:     Won Chung <wonchung@...gle.com>
Cc:     Jaroslav Kysela <perex@...ex.cz>, Takashi Iwai <tiwai@...e.com>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Benson Leung <bleung@...omium.org>,
        Prashant Malani <pmalani@...omium.org>,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH v2] sound/hda: Add NULL check to component match callback function

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@...ux.intel.com>
> Signed-off-by: Mika Westerberg <mika.westerberg@...ux.intel.com>
> Signed-off-by: Won Chung <wonchung@...gle.com>
> ---
> - Add "Fixes" tag
> - Send to stable@...r.kernel.org

You rather need to add "Cc: stable@...r.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