ALSA: usb-audio: Fix double-free in error paths after snd_usb_add_audio_stream() call

create_fixed_stream_quirk(), snd_usb_parse_audio_interface() and
create_uaxx_quirk() functions allocate the audioformat object by themselves
and free it upon error before returning. However, once the object is linked
to a stream, it's freed again in snd_usb_audio_pcm_free(), thus it'll be
double-freed, eventually resulting in a memory corruption.

This patch fixes these failures in the error paths by unlinking the audioformat
object before freeing it.

Based on a patch by Takashi Iwai <tiwai@suse.de>

[Note for stable backports:
 this patch requires the commit 902eb7fd1e4a ('ALSA: usb-audio: Minor
 code cleanup in create_fixed_stream_quirk()')]

Bug 1823317
Bug 1935735

Change-Id: I4f65a902a19e7b21e8bc0fa21efd833c8360a3cf
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1283358
Reported-by: Ralf Spenneberg <ralf@spenneberg.net>
Cc: <stable@vger.kernel.org> # see the note above
Signed-off-by: Vladis Dronov <vdronov@redhat.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Gagan Grover <ggrover@nvidia.com>
Reviewed-on: http://git-master/r/1259999
(cherry picked from commit 14e09c3233fb7578c778b70ec3933ba5cadfccb6)
Reviewed-on: https://git-master.nvidia.com/r/1690292
GVS: Gerrit_Virtual_Submit
Reviewed-by: Bibek Basu <bbasu@nvidia.com>
Tested-by: Amulya Yarlagadda <ayarlagadda@nvidia.com>
Reviewed-by: Winnie Hsu <whsu@nvidia.com>

2 files changed, 16 insertions, 7 deletions

diff --git a/sound/usb/quirks.c b/sound/usb/quirks.c
index 3879eae7e874..a72bfeee6de2 100644
--- a/sound/usb/quirks.c
+++ b/sound/usb/quirks.c
@@ -136,6 +136,7 @@ static int create_fixed_stream_quirk(struct snd_usb_audio *chip,
 		snd_printk(KERN_ERR "cannot memdup\n");
 		return -ENOMEM;
 	}
+	INIT_LIST_HEAD(&fp->list);
 	if (fp->nr_rates > MAX_NR_RATES) {
 		kfree(fp);
 		return -EINVAL;
@@ -154,15 +155,12 @@ static int create_fixed_stream_quirk(struct snd_usb_audio *chip,
 		? SNDRV_PCM_STREAM_CAPTURE : SNDRV_PCM_STREAM_PLAYBACK;
 	err = snd_usb_add_audio_stream(chip, stream, fp);
 	if (err < 0) {
-		kfree(fp);
-		kfree(rate_table);
-		return err;
+		goto error;
 	}
 	if (fp->iface != get_iface_desc(&iface->altsetting[0])->bInterfaceNumber ||
 	    fp->altset_idx >= iface->num_altsetting) {
-		kfree(fp);
-		kfree(rate_table);
-		return -EINVAL;
+		err = -EINVAL;
+		goto error;
 	}
 	alts = &iface->altsetting[fp->altset_idx];
 	if (fp->datainterval == 0)
@@ -173,6 +171,11 @@ static int create_fixed_stream_quirk(struct snd_usb_audio *chip,
 	snd_usb_init_pitch(chip, fp->iface, alts, fp);
 	snd_usb_init_sample_rate(chip, fp->iface, alts, fp, fp->rate_max);
 	return 0;
+error:
+	list_del(&fp->list); /* unlink for avoiding double-free */
+	kfree(fp);
+	kfree(rate_table);
+	return err;
 }
 
 /*
@@ -239,6 +242,7 @@ static int create_uaxx_quirk(struct snd_usb_audio *chip,
 	fp->ep_attr = get_endpoint(alts, 0)->bmAttributes;
 	fp->datainterval = 0;
 	fp->maxpacksize = le16_to_cpu(get_endpoint(alts, 0)->wMaxPacketSize);
+	INIT_LIST_HEAD(&fp->list);
 
 	switch (fp->maxpacksize) {
 	case 0x120:
@@ -262,6 +266,7 @@ static int create_uaxx_quirk(struct snd_usb_audio *chip,
 		? SNDRV_PCM_STREAM_CAPTURE : SNDRV_PCM_STREAM_PLAYBACK;
 	err = snd_usb_add_audio_stream(chip, stream, fp);
 	if (err < 0) {
+		list_del(&fp->list); /* unlink for avoiding double-free */
 		kfree(fp);
 		return err;
 	}
diff --git a/sound/usb/stream.c b/sound/usb/stream.c
index 5b6f7a027c6a..7ddf4a437e4a 100644
--- a/sound/usb/stream.c
+++ b/sound/usb/stream.c
@@ -307,7 +307,9 @@ static struct snd_pcm_chmap_elem *convert_chmap(int channels, unsigned int bits,
 /*
  * add this endpoint to the chip instance.
  * if a stream with the same endpoint already exists, append to it.
- * if not, create a new pcm stream.
+ * if not, create a new pcm stream. note, fp is added to the substream
+ * fmt_list and will be freed on the chip instance release. do not free
+ * fp or do remove it from the substream fmt_list to avoid double-free.
  */
 int snd_usb_add_audio_stream(struct snd_usb_audio *chip,
 			     int stream,
@@ -755,6 +757,7 @@ int snd_usb_parse_audio_interface(struct snd_usb_audio *chip, int iface_no)
 		fp->attributes = parse_uac_endpoint_attributes(chip, alts, protocol, iface_no);
 		fp->clock = clock;
 		fp->chmap = convert_chmap(num_channels, chconfig, protocol);
+		INIT_LIST_HEAD(&fp->list);
 
 		/* some quirks for attributes here */
 
@@ -799,6 +802,7 @@ int snd_usb_parse_audio_interface(struct snd_usb_audio *chip, int iface_no)
 		snd_printdd(KERN_INFO "%d:%u:%d: add audio endpoint %#x\n", dev->devnum, iface_no, altno, fp->endpoint);
 		err = snd_usb_add_audio_stream(chip, stream, fp);
 		if (err < 0) {
+			list_del(&fp->list); /* unlink for avoiding double-free */
 			kfree(fp->rate_table);
 			kfree(fp->chmap);
 			kfree(fp);