linux-kernel - Re: [PATCH]ALSA: HDA: Fix Oops caused by dereference NULL pointer

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Date:	Tue, 07 May 2013 07:34:59 +0200
From:	Takashi Iwai <tiwai@...e.de>
To:	Wang YanQing <udknight@...il.com>
Cc:	alsa-devel@...a-project.org, linux-kernel@...r.kernel.org,
	perex@...ex.cz, david.henningsson@...onical.com
Subject: Re: [PATCH]ALSA: HDA: Fix Oops caused by dereference NULL pointer

At Tue, 7 May 2013 11:27:33 +0800,
Wang YanQing wrote:
> 
> The interrupt handler azx_interrupt will call azx_update_rirb,
> which may call snd_hda_queue_unsol_event, snd_hda_queue_unsol_event
> will dereference chip->bus pointer.
> 
> The problem is we alloc chip->bus in azx_codec_create
> which will be called after we enable IRQ and enable unsolicited
> event in azx_probe.
> 
> This will cause Oops due dereference NULL pointer. I meet it, good luck:)
> 
> Signed-off-by: Wang YanQing <udknight@...il.com>

Thanks, applied with a slight fix (put before the tracepoint so that
it won't give more NULL dereference, and also put another NULL check
of bus->workq as done in hda_intel.c.)


Takashi

> ---
>  sound/pci/hda/hda_codec.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/sound/pci/hda/hda_codec.c b/sound/pci/hda/hda_codec.c
> index 622f726..9c76752 100644
> --- a/sound/pci/hda/hda_codec.c
> +++ b/sound/pci/hda/hda_codec.c
> @@ -618,6 +618,9 @@ int snd_hda_queue_unsol_event(struct hda_bus *bus, u32 res, u32 res_ex)
>  	unsigned int wp;
>  
>  	trace_hda_unsol_event(bus, res, res_ex);
> +	if (!bus)
> +		return 0;
> +
>  	unsol = bus->unsol;
>  	if (!unsol)
>  		return 0;
> -- 
> 1.7.12.4.dirty
> 
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