ALSA: ac97: Fix possible error value of *rac97

Before committing 79597c8bf64c, *rac97 always be NULL if there is
an error. When error happens, make sure *rac97 is NULL is safer.

For examble, in snd_vortex_mixer():
	err = snd_ac97_mixer(pbus, &ac97, &vortex->codec);
	vortex->isquad = ((vortex->codec == NULL) ?
		0 : (vortex->codec->ext_id&0x80));
If error happened but vortex->codec isn't NULL, this may cause some
problems.

Move the judgement order to be clearer and better.

Fixes: 79597c8bf64c ("ALSA: ac97: Fix possible NULL dereference in snd_ac97_mixer")
Suggested-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Acked-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Signed-off-by: Su Hui <suhui@nfschina.com>
Link: https://lore.kernel.org/r/20230823025212.1000961-1-suhui@nfschina.com
Signed-off-by: Takashi Iwai <tiwai@suse.de>

diff --git a/sound/pci/ac97/ac97_codec.c b/sound/pci/ac97/ac97_codec.c
index 80a65b8..25f93e5 100644 (file)
--- a/sound/pci/ac97/ac97_codec.c
+++ b/sound/pci/ac97/ac97_codec.c
@@ -2069,10 +2069,9 @@ int snd_ac97_mixer(struct snd_ac97_bus *bus, struct snd_ac97_template *template,
                .dev_disconnect =       snd_ac97_dev_disconnect,
        };
 
-       if (!rac97)
-               return -EINVAL;
-       if (snd_BUG_ON(!bus || !template))
+       if (snd_BUG_ON(!bus || !template || !rac97))
                return -EINVAL;
+       *rac97 = NULL;
        if (snd_BUG_ON(template->num >= 4))
                return -EINVAL;
        if (bus->codec[template->num])