[PATCH]ALSA: HDA: Fix Oops caused by dereference NULL pointer

[PATCH]ALSA: HDA: Fix Oops caused by dereference NULL pointer

[Wang YanQing]

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@gmail.com>
---
 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

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

[Takashi Iwai]

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@gmail.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
>