dma-buf: Fix memory leak in sync_file_merge()

commit 6645d42d upstream.

In the implementation of sync_file_merge() the allocated sync_file is
leaked if number of fences overflows. Release sync_file by goto err.

Fixes: a02b9dc9 ("dma-buf/sync_file: refactor fence storage in struct sync_file")
Signed-off-by: Navid Emamdoost <navid.emamdoost@gmail.com>
Cc: stable@vger.kernel.org
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20191122220957.30427-1-navid.emamdoost@gmail.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/dma-buf/sync_file.c

@@ -230,7 +230,7 @@ static struct sync_file *sync_file_merge(const char *name, struct sync_file *a,
 	a_fences = get_fences(a, &a_num_fences);
 	b_fences = get_fences(b, &b_num_fences);
 	if (a_num_fences > INT_MAX - b_num_fences)
-		return NULL;
+		goto err;
 
 	num_fences = a_num_fences + b_num_fences;