Commit 836b34a9 authored by Vladis Dronov's avatar Vladis Dronov Committed by Takashi Iwai
Browse files

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 902eb7fd ('ALSA: usb-audio: Minor
 code cleanup in create_fixed_stream_quirk()')]

Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1283358


Reported-by: default avatarRalf Spenneberg <ralf@spenneberg.net>
Cc: <stable@vger.kernel.org> # see the note above
Signed-off-by: default avatarVladis Dronov <vdronov@redhat.com>
Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
parent 8eb22214

sound/usb/quirks.c

+4 −0
Original line number Diff line number Diff line
@@ -150,6 +150,7 @@ static int create_fixed_stream_quirk(struct snd_usb_audio *chip, 
		usb_audio_err(chip, "cannot memdup\n");

		return -ENOMEM;

	}

	INIT_LIST_HEAD(&fp->list);

	if (fp->nr_rates > MAX_NR_RATES) {

		kfree(fp);

		return -EINVAL;
@@ -193,6 +194,7 @@ static int create_fixed_stream_quirk(struct snd_usb_audio *chip, 
	return 0;



 error:

	list_del(&fp->list); /* unlink for avoiding double-free */

	kfree(fp);

	kfree(rate_table);

	return err;
@@ -469,6 +471,7 @@ 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:
@@ -492,6 +495,7 @@ 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;

	}

sound/usb/stream.c

+5 −1
Original line number Diff line number Diff line
@@ -314,7 +314,9 @@ 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,
@@ -675,6 +677,7 @@ int snd_usb_parse_audio_interface(struct snd_usb_audio *chip, int iface_no) 
					* (fp->maxpacksize & 0x7ff);

		fp->attributes = parse_uac_endpoint_attributes(chip, alts, protocol, iface_no);

		fp->clock = clock;

		INIT_LIST_HEAD(&fp->list);



		/* some quirks for attributes here */
@@ -723,6 +726,7 @@ int snd_usb_parse_audio_interface(struct snd_usb_audio *chip, int iface_no) 
		dev_dbg(&dev->dev, "%u:%d: add audio endpoint %#x\n", 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);

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