Patch "ASoC: Fix use-after-free at card unregistration" has been added to the 4.4-stable tree

This is a note to let you know that I've just added the patch titled

ASoC: Fix use-after-free at card unregistration

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
asoc-fix-use-after-free-at-card-unregistration.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Takashi Iwai <[email protected]>
Date: Wed, 24 May 2017 10:19:45 +0200
Subject: ASoC: Fix use-after-free at card unregistration

From: Takashi Iwai <[email protected]>

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.

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

@@ -1775,6 +1775,9 @@ static int soc_cleanup_card_resources(st
 	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);
 

@@ -1786,9 +1789,7 @@ static int soc_cleanup_card_resources(st
 
 	snd_soc_dapm_free(&card->dapm);
 
-	snd_card_free(card->snd_card);
 	return 0;
-
 }
 
 /* removes a socdev */

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/alsa-timer-fix-race-between-read-and-ioctl.patch queue-4.4/alsa-timer-fix-missing-queue-indices-reset-at-sndrv_timer_ioctl_select.patch queue-4.4/asoc-fix-use-after-free-at-card-unregistration.patch queue-4.4/ptrace-properly-initialize-ptracer_cred-on-fork.patch