avformat/nsvdec: Fix memleaks on errors while reading the header

Fixes: memleaks
Fixes: 21084/clusterfuzz-testcase-minimized-ffmpeg_DEMUXER_fuzzer-5655975492321280

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Reviewed-by: Paul B Mahol <onemda@gmail.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
(cherry picked from commit 96c0469455)
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavformat/nsvdec.c

@@ -211,6 +211,7 @@ static const AVCodecTag nsv_codec_audio_tags[] = {
 
 //static int nsv_load_index(AVFormatContext *s);
 static int nsv_read_chunk(AVFormatContext *s, int fill_header);
+static int nsv_read_close(AVFormatContext *s);
 
 /* try to find something we recognize, and set the state accordingly */
 static int nsv_resync(AVFormatContext *s)
@@ -492,25 +493,32 @@ static int nsv_read_header(AVFormatContext *s)
     nsv->ahead[0].data = nsv->ahead[1].data = NULL;
 
     for (i = 0; i < NSV_MAX_RESYNC_TRIES; i++) {
-        if (nsv_resync(s) < 0)
-            return -1;
+        err = nsv_resync(s);
+        if (err < 0)
+            goto fail;
         if (nsv->state == NSV_FOUND_NSVF) {
             err = nsv_parse_NSVf_header(s);
             if (err < 0)
-                return err;
+                goto fail;
         }
             /* we need the first NSVs also... */
         if (nsv->state == NSV_FOUND_NSVS) {
             err = nsv_parse_NSVs_header(s);
             if (err < 0)
-                return err;
+                goto fail;
             break; /* we just want the first one */
         }
     }
-    if (s->nb_streams < 1) /* no luck so far */
-        return -1;
+    if (s->nb_streams < 1) { /* no luck so far */
+        err = AVERROR_INVALIDDATA;
+        goto fail;
+    }
+
     /* now read the first chunk, so we can attempt to decode more info */
     err = nsv_read_chunk(s, 1);
+fail:
+    if (err < 0)
+        nsv_read_close(s);
 
     av_log(s, AV_LOG_TRACE, "parsed header\n");
     return err;