V4L/DVB (6305): V4L: videobuf-core.c avoid NULL dereferences in videobuf-core

The return value of videobuf_alloc() is unchecked but this function will
return NULL on an error.  Check for NULL and make videobuf_reqbufs()
return the number of successfully allocated buffers.

Also, fix saa7146_video.c and bttv-driver.c to use this returned
buffer count.

Tested against the vivi driver.  Not tested against saa7146 or bt8xx
devices.

Signed-off-by: Brandon Philips <bphilips@suse.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>

1 files changed, 2 insertions, 0 deletions

diff --git a/drivers/media/common/saa7146_video.c b/drivers/media/common/saa7146_video.c
index 29dbc602a484..f245a3b2ef47 100644
--- a/drivers/media/common/saa7146_video.c
+++ b/drivers/media/common/saa7146_video.c
@@ -1212,6 +1212,8 @@ int saa7146_video_do_ioctl(struct inode *inode, struct file *file, unsigned int
                         mutex_unlock(&q->lock);
                         return err;
                 }
+
+                gbuffers = err;
                 memset(mbuf,0,sizeof(*mbuf));
                 mbuf->frames = gbuffers;
                 mbuf->size   = gbuffers * gbufsize;