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Subject[PATCH] ASoC: topology: Avoid card NULL deref in snd_soc_tplg_component_remove()
Date
Don't deference card in comp->card->snd_card before checking for NULL card.

During the unloading of ASoC kernel modules, there is a kernel oops in
snd_soc_tplg_component_remove() that happens because comp->card is set to
NULL in soc_cleanup_component().

Cc: Liam Girdwood <lgirdwood@gmail.com>
Cc: Mark Brown <broonie@kernel.org>
Cc: Jaroslav Kysela <perex@perex.cz>
Cc: Takashi Iwai <tiwai@suse.com>
Cc: alsa-devel@alsa-project.org
Cc: linux-kernel@vger.kernel.org
Cc: stable@vger.kernel.org
Fixes: 7e567b5ae063 ("ASoC: topology: Add missing rwsem around snd_ctl_remove() calls")
Signed-off-by: Dean Gehnert <deang@tpi.com>
---
sound/soc/soc-topology.c | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/sound/soc/soc-topology.c b/sound/soc/soc-topology.c
index 3f9d314fba16..cf0efe1147c2 100644
--- a/sound/soc/soc-topology.c
+++ b/sound/soc/soc-topology.c
@@ -2613,15 +2613,18 @@ EXPORT_SYMBOL_GPL(snd_soc_tplg_component_load);
/* remove dynamic controls from the component driver */
int snd_soc_tplg_component_remove(struct snd_soc_component *comp)
{
- struct snd_card *card = comp->card->snd_card;
+ struct snd_card *card;
struct snd_soc_dobj *dobj, *next_dobj;
int pass;

/* process the header types from end to start */
for (pass = SOC_TPLG_PASS_END; pass >= SOC_TPLG_PASS_START; pass--) {

+ card = (comp->card) ? comp->card->snd_card : NULL;
+
/* remove mixer controls */
- down_write(&card->controls_rwsem);
+ if (card)
+ down_write(&card->controls_rwsem);
list_for_each_entry_safe(dobj, next_dobj, &comp->dobj_list,
list) {

@@ -2660,7 +2663,8 @@ int snd_soc_tplg_component_remove(struct snd_soc_component *comp)
break;
}
}
- up_write(&card->controls_rwsem);
+ if (card)
+ up_write(&card->controls_rwsem);
}

/* let caller know if FW can be freed when no objects are left */
--
2.17.1
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