avformat/rl2: Fix DoS due to lack of eof check

Fixes: loop.rl2

Found-by: Xiaohei and Wangchu from Alibaba Security Team
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavformat/rl2.c

@@ -170,12 +170,21 @@ static av_cold int rl2_read_header(AVFormatContext *s)
     }
 
     /** read offset and size tables */
-    for(i=0; i < frame_count;i++)
+    for(i=0; i < frame_count;i++) {
+        if (avio_feof(pb))
+            return AVERROR_INVALIDDATA;
         chunk_size[i] = avio_rl32(pb);
-    for(i=0; i < frame_count;i++)
+    }
+    for(i=0; i < frame_count;i++) {
+        if (avio_feof(pb))
+            return AVERROR_INVALIDDATA;
         chunk_offset[i] = avio_rl32(pb);
-    for(i=0; i < frame_count;i++)
+    }
+    for(i=0; i < frame_count;i++) {
+        if (avio_feof(pb))
+            return AVERROR_INVALIDDATA;
         audio_size[i] = avio_rl32(pb) & 0xFFFF;
+    }
 
     /** build the sample index */
     for(i=0;i<frame_count;i++){