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ASoC: Fix use-after-free at card unregistration 

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>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
This commit is contained in:
Takashi Iwai 2017-05-24 10:19:45 +02:00 committed by syphyr
parent 2f97a86170
commit 652ea8e9d4
1 changed files with 3 additions and 2 deletions
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5
sound/soc/soc-core.c
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@ -1901,6 +1901,9 @@ static int soc_cleanup_card_resources(struct snd_soc_card *card)
for (i = 0; i < card->num_aux_devs; i++)
soc_remove_aux_dev(card, i);
/* 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);
@ -1912,9 +1915,7 @@ static int soc_cleanup_card_resources(struct snd_soc_card *card)
snd_soc_dapm_free(&card->dapm);
snd_card_free(card->snd_card);
return 0;
}
/* removes a socdev */