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>

3 files changed, 19 insertions, 1 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;
diff --git a/drivers/media/video/em28xx/em28xx-audio.c b/drivers/media/video/em28xx/em28xx-audio.c
index 343dff0f8a04..3c006103c1eb 100644
--- a/drivers/media/video/em28xx/em28xx-audio.c
+++ b/drivers/media/video/em28xx/em28xx-audio.c
@@ -268,6 +268,12 @@ static int snd_em28xx_capture_open(struct snd_pcm_substream *substream)
 
         dprintk("opening device and trying to acquire exclusive lock\n");
 
+        if (!dev) {
+                printk(KERN_ERR "BUG: em28xx can't find device struct."
+                                " Can't proceed with open\n");
+                return -ENODEV;
+        }
+
         /* Sets volume, mute, etc */
 
         dev->mute = 0;
diff --git a/drivers/media/video/saa7134/saa7134-alsa.c b/drivers/media/video/saa7134/saa7134-alsa.c
index ba3082422a01..f118de6e3672 100644
--- a/drivers/media/video/saa7134/saa7134-alsa.c
+++ b/drivers/media/video/saa7134/saa7134-alsa.c
@@ -613,9 +613,15 @@ static int snd_card_saa7134_capture_open(struct snd_pcm_substream * substream)
         struct snd_pcm_runtime *runtime = substream->runtime;
         snd_card_saa7134_pcm_t *pcm;
         snd_card_saa7134_t *saa7134 = snd_pcm_substream_chip(substream);
-        struct saa7134_dev *dev = saa7134->dev;
+        struct saa7134_dev *dev;
         int amux, err;
 
+        if (!saa7134) {
+                printk(KERN_ERR "BUG: saa7134 can't find device struct."
+                                " Can't proceed with open\n");
+                return -ENODEV;
+        }
+        dev = saa7134->dev;
         mutex_lock(&dev->dmasound.lock);
 
         dev->dmasound.read_count  = 0;