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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 902eb7fd1e ('ALSA: usb-audio: Minor
 code cleanup in create_fixed_stream_quirk()')]

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>
This commit is contained in:
Vladis Dronov 2016-03-31 12:05:43 -04:00 committed by Takashi Iwai
parent 8eb22214b7
commit 836b34a935
2 changed files with 9 additions and 1 deletions
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4
sound/usb/quirks.c
View File

@ -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;
}

6
sound/usb/stream.c
View File

@ -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);