CHROMIUM: dma-buf: restore args on failure of dma_buf_mmap

Callers to dma_buf_mmap expect to fput() the vma struct's vm_file
themselves on failure.  Not restoring the struct's data on failure
causes a double-decrement of the vm_file's refcount.

Signed-off-by: John Sheu <sheu@google.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Sumit Semwal <sumit.semwal@linaro.org>

drivers/base/dma-buf.c

@@ -447,6 +447,9 @@ EXPORT_SYMBOL_GPL(dma_buf_kunmap);
 int dma_buf_mmap(struct dma_buf *dmabuf, struct vm_area_struct *vma,
 		 unsigned long pgoff)
 {
+	struct file *oldfile;
+	int ret;
+
 	if (WARN_ON(!dmabuf || !vma))
 		return -EINVAL;
 
@@ -460,14 +463,22 @@ int dma_buf_mmap(struct dma_buf *dmabuf, struct vm_area_struct *vma,
 		return -EINVAL;
 
 	/* readjust the vma */
-	if (vma->vm_file)
-		fput(vma->vm_file);
-
-	vma->vm_file = get_file(dmabuf->file);
-
+	get_file(dmabuf->file);
+	oldfile = vma->vm_file;
+	vma->vm_file = dmabuf->file;
 	vma->vm_pgoff = pgoff;
 
-	return dmabuf->ops->mmap(dmabuf, vma);
+	ret = dmabuf->ops->mmap(dmabuf, vma);
+	if (ret) {
+		/* restore old parameters on failure */
+		vma->vm_file = oldfile;
+		fput(dmabuf->file);
+	} else {
+		if (oldfile)
+			fput(oldfile);
+	}
+	return ret;
+
 }
 EXPORT_SYMBOL_GPL(dma_buf_mmap);