[alsa-devel] 3.6-rc Cirrus HDA reconfig oops...

[Takashi Iwai]

At Sun, 9 Sep 2012 13:02:16 +0800,
Daniel J Blueman wrote:
> 
> With a non-specialised Cirrus HDA codec, it's readily possible to
> cause a kernel oops as root with 3.6-rc kernels [1].
> 
> patch_cirrus.c:
> 
> static int cs_init(struct hda_codec *codec)
> {
> 	struct cs_spec *spec = codec->spec;
> 
> 	/* init_verb sequence for C0/C1/C2 errata*/
> 	snd_hda_sequence_write(codec, cs_errata_init_verbs);
> 
> 	snd_hda_sequence_write(codec, cs_coef_init_verbs);
> 
> 	if (spec->gpio_mask) {
> 		snd_hda_codec_write(codec, 0x01, 0, AC_VERB_SET_GPIO_MASK,
> 				    spec->gpio_mask);
> 
> Here, spec is NULL, so loading spec->gpio_mask causes a fatal
> pagefault at address 0x180 (ie the offset of gpio_mask in the struct).
> I was going to prepare a patch to guard for this, but since spec is
> expected in so many places, there is a likely a behavioural issue
> preventing a spec struct being generated.
> 
> Let me know for further testing and debug.

It's because of calling a leftover callback.
The patch below should fix the issue.  I'll queue it up to for-linus
branch.


thanks,

Takashi

---
From: Takashi Iwai <tiwai at suse.de>
Subject: [PATCH] ALSA: hda - Fix Oops at codec reset/reconfig

snd_hda_codec_reset() calls restore_pincfgs() where the codec is
powered up again, which eventually tries to resume and initialize via
the callbacks of the codec.  However, it's the place just after codec
free callback, thus no codec callbacks should be called after that.
On a codec like CS4206, it results in Oops due to the access in init
callback.

This patch fixes the issue by clearing the codec callbacks properly
after freeing codec.

Reported-by: Daniel J Blueman <daniel at quora.org>
Cc: <stable at vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai at suse.de>
---
 sound/pci/hda/hda_codec.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/sound/pci/hda/hda_codec.c b/sound/pci/hda/hda_codec.c
index f25c24c..aa4cbca 100644
--- a/sound/pci/hda/hda_codec.c
+++ b/sound/pci/hda/hda_codec.c
@@ -2353,6 +2353,7 @@ int snd_hda_codec_reset(struct hda_codec *codec)
 	}
 	if (codec->patch_ops.free)
 		codec->patch_ops.free(codec);
+	memset(&codec->patch_ops, 0, sizeof(codec->patch_ops));
 	snd_hda_jack_tbl_clear(codec);
 	codec->proc_widget_hook = NULL;
 	codec->spec = NULL;
-- 
1.7.11.5