V4L/DVB (8026): Avoids an OOPS if dev struct can't be successfully recovered

On some alsa versions, it seems that snd_pcm_substream_chip(substream)
is returning a NULL pointer. This causes an OOPS, as reported by:

https://bugs.launchpad.net/ubuntu/+source/linux-ubuntu-modules-2.6.24/+bug/212271
https://bugs.launchpad.net/ubuntu/+source/alsa-driver/+bug/212960

This patch avoids the OOPS by not letting and open() succeed.

Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>

1 files changed, 6 insertions, 0 deletions

diff --git a/drivers/media/video/cx88/cx88-alsa.c b/drivers/media/video/cx88/cx88-alsa.c
index e976fc6bef7c..80c8883e54b5 100644
--- a/drivers/media/video/cx88/cx88-alsa.c
+++ b/drivers/media/video/cx88/cx88-alsa.c
@@ -332,6 +332,12 @@ static int snd_cx88_pcm_open(struct snd_pcm_substream *substream)
         struct snd_pcm_runtime *runtime = substream->runtime;
         int err;
 
+        if (!chip) {
+                printk(KERN_ERR "BUG: cx88 can't find device struct."
+                                " Can't proceed with open\n");
+                return -ENODEV;
+        }
+
         err = snd_pcm_hw_constraint_pow2(runtime, 0, SNDRV_PCM_HW_PARAM_PERIODS);
         if (err < 0)
                 goto _error;