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Subject[PATCH 4.9 104/119] ASoC: Fix use-after-free at card unregistration
Date
4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Takashi Iwai <tiwai@suse.de>

commit 4efda5f2130da033aeedc5b3205569893b910de2 upstream.

soc_cleanup_card_resources() call snd_card_free() at the last of its
procedure. This turned out to lead to a use-after-free.
PCM runtimes have been already removed via soc_remove_pcm_runtimes(),
while it's dereferenced later in soc_pcm_free() called via
snd_card_free().

The fix is simple: just move the snd_card_free() call to the beginning
of the whole procedure. This also gives another benefit: it
guarantees that all operations have been shut down before actually
releasing the resources, which was racy until now.

Reported-and-tested-by: Robert Jarzmik <robert.jarzmik@free.fr>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
sound/soc/soc-core.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

--- a/sound/soc/soc-core.c
+++ b/sound/soc/soc-core.c
@@ -2076,6 +2076,9 @@ static int soc_cleanup_card_resources(st
list_for_each_entry(rtd, &card->rtd_list, list)
flush_delayed_work(&rtd->delayed_work);

+ /* free the ALSA card at first; this syncs with pending operations */
+ snd_card_free(card->snd_card);
+
/* remove and free each DAI */
soc_remove_dai_links(card);
soc_remove_pcm_runtimes(card);
@@ -2090,9 +2093,7 @@ static int soc_cleanup_card_resources(st
if (card->remove)
card->remove(card);

- snd_card_free(card->snd_card);
return 0;
-
}

/* removes a socdev */

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