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>

3 files changed, 17 insertions, 5 deletions

diff --git a/drivers/media/common/saa7146_video.c b/drivers/media/common/saa7146_video.c
index 29dbc602a48..f245a3b2ef4 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;
diff --git a/drivers/media/video/bt8xx/bttv-driver.c b/drivers/media/video/bt8xx/bttv-driver.c
index 49278537eec..7a332b3efe5 100644
--- a/drivers/media/video/bt8xx/bttv-driver.c
+++ b/drivers/media/video/bt8xx/bttv-driver.c
@@ -3072,6 +3072,8 @@ static int bttv_do_ioctl(struct inode *inode, struct file *file,
                                              V4L2_MEMORY_MMAP);
                 if (retval < 0)
                         goto fh_unlock_and_return;
+
+                gbuffers = retval;
                 memset(mbuf,0,sizeof(*mbuf));
                 mbuf->frames = gbuffers;
                 mbuf->size   = gbuffers * gbufsize;
diff --git a/drivers/media/video/videobuf-core.c b/drivers/media/video/videobuf-core.c
index f5c5ea8b6b0..25a98496e3d 100644
--- a/drivers/media/video/videobuf-core.c
+++ b/drivers/media/video/videobuf-core.c
@@ -329,7 +329,7 @@ int videobuf_reqbufs(struct videobuf_queue *q,
                 goto done;
         }
 
-        req->count = count;
+        req->count = retval;
 
  done:
         mutex_unlock(&q->lock);
@@ -698,7 +698,7 @@ int videobuf_read_start(struct videobuf_queue *q)
 {
         enum v4l2_field field;
         unsigned long flags=0;
-        int count = 0, size = 0;
+        unsigned int count = 0, size = 0;
         int err, i;
 
         q->ops->buf_setup(q,&count,&size);
@@ -709,9 +709,11 @@ int videobuf_read_start(struct videobuf_queue *q)
         size = PAGE_ALIGN(size);
 
         err = videobuf_mmap_setup(q, count, size, V4L2_MEMORY_USERPTR);
-        if (err)
+        if (err < 0)
                 return err;
 
+        count = err;
+
         for (i = 0; i < count; i++) {
                 field = videobuf_next_field(q);
                 err = q->ops->buf_prepare(q,q->bufs[i],field);
@@ -876,6 +878,9 @@ int videobuf_mmap_setup(struct videobuf_queue *q,
         for (i = 0; i < bcount; i++) {
                 q->bufs[i] = videobuf_alloc(q);
 
+                if (q->bufs[i] == NULL)
+                        break;
+
                 q->bufs[i]->i      = i;
                 q->bufs[i]->input  = UNSET;
                 q->bufs[i]->memory = memory;
@@ -891,10 +896,13 @@ int videobuf_mmap_setup(struct videobuf_queue *q,
                 }
         }
 
+        if (!i)
+                return -ENOMEM;
+
         dprintk(1,"mmap setup: %d buffers, %d bytes each\n",
-                bcount,bsize);
+                i, bsize);
 
-        return 0;
+        return i;
 }
 
 int videobuf_mmap_free(struct videobuf_queue *q)