[PATCH] drivers/media/v4l2-core/v4l2-h264.c : add detection of null pointers

[Dong Chuanjian]

Continue the program when the pointer assignment is successful.

Signed-off-by: Dong Chuanjian <chuanjian@xxxxxxxxxxxx>

diff --git a/drivers/media/v4l2-core/v4l2-h264.c b/drivers/media/v4l2-core/v4l2-h264.c
index 72bd64f65198..1163cd48ff33 100644
--- a/drivers/media/v4l2-core/v4l2-h264.c
+++ b/drivers/media/v4l2-core/v4l2-h264.c
@@ -343,18 +343,19 @@ static const char *format_ref_list_b(const struct v4l2_h264_reflist_builder *bui
 	int n = 0, i;
 
 	*out_str = kmalloc(tmp_str_size, GFP_KERNEL);
-
-	n += snprintf(*out_str + n, tmp_str_size - n, "|");
-
-	for (i = 0; i < builder->num_valid; i++) {
-		int frame_num = builder->refs[reflist[i].index].frame_num;
-		u32 poc = v4l2_h264_get_poc(builder, reflist + i);
-		bool longterm = builder->refs[reflist[i].index].longterm;
-
-		n += scnprintf(*out_str + n, tmp_str_size - n, "%i%c%c|",
-			       longterm ? frame_num : poc,
-			       longterm ? 'l' : 's',
-			       ref_type_to_char(reflist[i].fields));
+	if (*out_str != NULL) {
+		n += snprintf(*out_str + n, tmp_str_size - n, "|");
+
+		for (i = 0; i < builder->num_valid; i++) {
+			int frame_num = builder->refs[reflist[i].index].frame_num;
+			u32 poc = v4l2_h264_get_poc(builder, reflist + i);
+			bool longterm = builder->refs[reflist[i].index].longterm;
+
+			n += scnprintf(*out_str + n, tmp_str_size - n, "%i%c%c|",
+				       longterm ? frame_num : poc,
+				       longterm ? 'l' : 's',
+				       ref_type_to_char(reflist[i].fields));
+		}
 	}
 
 	return *out_str;
-- 
2.18.2