From: Vladis Dronov <vdro...@redhat.com>
Subject: [PATCH] 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" <ti...@suse.de>
[Note for stable backports:
this patch requires the commit 902eb7fd1e4a ('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 <r...@spenneberg.net>
Cc: <sta...@vger.kernel.org> # see the note above
Signed-off-by: Vladis Dronov <vdro...@redhat.com>
---
sound/usb/quirks.c | 4 ++++
sound/usb/stream.c | 6 +++++-
2 files changed, 9 insertions(+), 1 deletion(-)
diff --git a/sound/usb/quirks.c b/sound/usb/quirks.c
index fb62bce..6178bb5 100644
--- a/sound/usb/quirks.c
+++ b/sound/usb/quirks.c
@@ -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;
}
diff --git a/sound/usb/stream.c b/sound/usb/stream.c
index 51258a1..6fe7f21 100644
--- a/sound/usb/stream.c
+++ b/sound/usb/stream.c
@@ -316,7 +316,9 @@ 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,
@@ -677,6 +679,7 @@ 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 */
@@ -725,6 +728,7 @@ 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);
--
2.5.5
