USB: gadget: audio driver seg-fault fix

The included patch can be applied to the new usb gadget audio driver.

It addresses a seg-fault in uncovered in g_audio.ko.
The fault occurs in the function u_audio.c::gaudio_open_end_dev() when
device /dev/snd/pcmC0D0c (FILE_PCM_CAPTURE) is not present.

I suspect there may be similar problems with device /dev/snd/pcmC0D0p
(FILE_PCM_PLAYBACK) handling also.  I leave that for the developer(s),
as I was unsure as to the side-effects of not calling
playback_default_hw_params() in the initialization phase.

Signed-off-by: Robin Callender <robin_callender@hotmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 6 insertions, 4 deletions

diff --git a/drivers/usb/gadget/u_audio.c b/drivers/usb/gadget/u_audio.c
index 0f3d22fc030e..b5200d551458 100644
--- a/drivers/usb/gadget/u_audio.c
+++ b/drivers/usb/gadget/u_audio.c
@@ -253,11 +253,13 @@ static int gaudio_open_snd_dev(struct gaudio *card)
         snd->filp = filp_open(fn_cap, O_RDONLY, 0);
         if (IS_ERR(snd->filp)) {
                 ERROR(card, "No such PCM capture device: %s\n", fn_cap);
-                snd->filp = NULL;
+                snd->substream = NULL;
+                snd->card = NULL;
+        } else {
+                pcm_file = snd->filp->private_data;
+                snd->substream = pcm_file->substream;
+                snd->card = card;
         }
-        pcm_file = snd->filp->private_data;
-        snd->substream = pcm_file->substream;
-        snd->card = card;
 
         return 0;
 }