avformat/mpc8: Check and propagate more errors

Fixes: Timeout
Fixes: 48846/clusterfuzz-testcase-minimized-ffmpeg_dem_MPC8_fuzzer-5278532493770752

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

libavformat/mpc8.c

@@ -135,37 +135,40 @@ static void mpc8_get_chunk_header(AVIOContext *pb, int *tag, int64_t *size)
         *size += pos;
 }
 
-static void mpc8_parse_seektable(AVFormatContext *s, int64_t off)
+static int mpc8_parse_seektable(AVFormatContext *s, int64_t off)
 {
     MPCContext *c = s->priv_data;
     int tag;
     int64_t size, pos, ppos[2];
     uint8_t *buf;
     int i, t, seekd, ret;
+    int64_t ret64;
     GetBitContext gb;
 
     if (s->nb_streams == 0) {
         av_log(s, AV_LOG_ERROR, "No stream added before parsing seek table\n");
-        return;
+        return AVERROR_INVALIDDATA;
     }
 
-    avio_seek(s->pb, off, SEEK_SET);
+    ret64 = avio_seek(s->pb, off, SEEK_SET);
+    if (ret64 < 0)
+        return AVERROR_INVALIDDATA;
     mpc8_get_chunk_header(s->pb, &tag, &size);
-    if(tag != TAG_SEEKTABLE){
+    if(tag != TAG_SEEKTABLE || avio_feof(s->pb)){
         av_log(s, AV_LOG_ERROR, "No seek table at given position\n");
-        return;
+        return AVERROR_INVALIDDATA;
     }
     if (size > INT_MAX/10 || size<=0) {
         av_log(s, AV_LOG_ERROR, "Bad seek table size\n");
-        return;
+        return AVERROR_INVALIDDATA;
     }
     if(!(buf = av_malloc(size + AV_INPUT_BUFFER_PADDING_SIZE)))
-        return;
+        return AVERROR(ENOMEM);
     ret = avio_read(s->pb, buf, size);
     if (ret != size) {
         av_log(s, AV_LOG_ERROR, "seek table truncated\n");
         av_free(buf);
-        return;
+        return AVERROR_INVALIDDATA;
     }
     memset(buf+size, 0, AV_INPUT_BUFFER_PADDING_SIZE);
 
@@ -174,14 +177,14 @@ static void mpc8_parse_seektable(AVFormatContext *s, int64_t off)
     if(size > UINT_MAX/4 || size > c->samples/1152){
         av_log(s, AV_LOG_ERROR, "Seek table is too big\n");
         av_free(buf);
-        return;
+        return AVERROR_INVALIDDATA;
     }
     seekd = get_bits(&gb, 4);
     for(i = 0; i < 2; i++){
         pos = gb_get_v(&gb);
         if (av_sat_add64(pos, c->header_pos) != pos + (uint64_t)c->header_pos) {
             av_free(buf);
-            return;
+            return AVERROR_INVALIDDATA;
         }
 
         pos += c->header_pos;
@@ -191,7 +194,7 @@ static void mpc8_parse_seektable(AVFormatContext *s, int64_t off)
     for(; i < size; i++){
         if (get_bits_left(&gb) < 13) {
             av_free(buf);
-            return;
+            return AVERROR_INVALIDDATA;
         }
         t = get_unary(&gb, 1, 33) << 12;
         t += get_bits(&gb, 12);
@@ -203,26 +206,31 @@ static void mpc8_parse_seektable(AVFormatContext *s, int64_t off)
         ppos[0] = pos;
     }
     av_free(buf);
+    return 0;
 }
 
-static void mpc8_handle_chunk(AVFormatContext *s, int tag, int64_t chunk_pos, int64_t size)
+static int mpc8_handle_chunk(AVFormatContext *s, int tag, int64_t chunk_pos, int64_t size)
 {
     AVIOContext *pb = s->pb;
     int64_t pos, off;
+    int ret;
 
     switch(tag){
     case TAG_SEEKTBLOFF:
         pos = avio_tell(pb);
         off = ffio_read_varlen(pb);
         if (pos > INT64_MAX - size || off < 0 || off > INT64_MAX - chunk_pos)
-            return;
+            return AVERROR_INVALIDDATA;
         pos += size;
-        mpc8_parse_seektable(s, chunk_pos + off);
+        ret = mpc8_parse_seektable(s, chunk_pos + off);
+        if (ret < 0)
+            return AVERROR_INVALIDDATA;
         avio_seek(pb, pos, SEEK_SET);
         break;
     default:
         avio_skip(pb, size);
     }
+    return 0;
 }
 
 static int mpc8_read_header(AVFormatContext *s)
@@ -249,7 +257,9 @@ static int mpc8_read_header(AVFormatContext *s)
         }
         if(tag == TAG_STREAMHDR)
             break;
-        mpc8_handle_chunk(s, tag, pos, size);
+        ret = mpc8_handle_chunk(s, tag, pos, size);
+        if (ret < 0)
+            return ret;
     }
     if(tag != TAG_STREAMHDR){
         av_log(s, AV_LOG_ERROR, "Stream header not found\n");