ALSA: usb-audio: Fix double-free in error paths after snd_usb_add_audio_stream()...
Vladis Dronov [Thu, 31 Mar 2016 16:05:43 +0000 (12:05 -0400)]
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

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
GVS: Gerrit_Virtual_Submit
Reviewed-by: Mitch Luban <mluban@nvidia.com>

sound/usb/quirks.c
sound/usb/stream.c

index 94cd28c..8256d01 100644 (file)
@@ -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;
        }
index 1f75ed5..c31e082 100644 (file)
@@ -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);