avformat/wc3movie: Cleanup on wc3_read_header() failure

Fixes: memleak
Fixes: 23660/clusterfuzz-testcase-minimized-ffmpeg_DEMUXER_fuzzer-6007508031504384

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavformat/wc3movie.c

@@ -139,10 +139,14 @@ static int wc3_read_header(AVFormatContext *s)
             /* load up the name */
             buffer = av_malloc(size+1);
             if (!buffer)
-                return AVERROR(ENOMEM);
+            if (!buffer) {
+                ret = AVERROR(ENOMEM);
+                goto fail;
+            }
             if ((ret = avio_read(pb, buffer, size)) != size) {
                 av_freep(&buffer);
-                return AVERROR(EIO);
+                ret =  AVERROR(EIO);
+                goto fail;
             }
             buffer[size] = 0;
             av_dict_set(&s->metadata, "title", buffer,
@@ -164,21 +168,26 @@ static int wc3_read_header(AVFormatContext *s)
         default:
             av_log(s, AV_LOG_ERROR, "unrecognized WC3 chunk: %s\n",
                    av_fourcc2str(fourcc_tag));
-            return AVERROR_INVALIDDATA;
+            ret = AVERROR_INVALIDDATA;
+            goto fail;
         }
 
         fourcc_tag = avio_rl32(pb);
         /* chunk sizes are 16-bit aligned */
         size = (avio_rb32(pb) + 1) & (~1);
-        if (avio_feof(pb))
-            return AVERROR(EIO);
+        if (avio_feof(pb)) {
+            ret = AVERROR(EIO);
+            goto fail;
+        }
 
     } while (fourcc_tag != BRCH_TAG);
 
     /* initialize the decoder streams */
     st = avformat_new_stream(s, NULL);
-    if (!st)
-        return AVERROR(ENOMEM);
+    if (!st) {
+        ret = AVERROR(ENOMEM);
+        goto fail;
+    }
     avpriv_set_pts_info(st, 33, 1, WC3_FRAME_FPS);
     wc3->video_stream_index = st->index;
     st->codecpar->codec_type = AVMEDIA_TYPE_VIDEO;
@@ -188,8 +197,10 @@ static int wc3_read_header(AVFormatContext *s)
     st->codecpar->height = wc3->height;
 
     st = avformat_new_stream(s, NULL);
-    if (!st)
-        return AVERROR(ENOMEM);
+    if (!st) {
+        ret = AVERROR(ENOMEM);
+        goto fail;
+    }
     avpriv_set_pts_info(st, 33, 1, WC3_FRAME_FPS);
     wc3->audio_stream_index = st->index;
     st->codecpar->codec_type = AVMEDIA_TYPE_AUDIO;
@@ -204,6 +215,9 @@ static int wc3_read_header(AVFormatContext *s)
     st->codecpar->block_align = WC3_AUDIO_BITS * WC3_AUDIO_CHANNELS;
 
     return 0;
+fail:
+    wc3_read_close(s);
+    return ret;
 }
 
 static int wc3_read_packet(AVFormatContext *s,