Check for several overreads, fixes issue 2512.

Patch by Daniel Kang, daniel.d.kang at gmail

Originally committed as revision 26289 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/truemotion2.c

@@ -260,7 +260,8 @@ static int tm2_read_deltas(TM2Context *ctx, int stream_id) {
     return 0;
 }
 
-static int tm2_read_stream(TM2Context *ctx, const uint8_t *buf, int stream_id) {
+static int tm2_read_stream(TM2Context *ctx, const uint8_t *buf, int stream_id, int buf_size)
+{
     int i;
     int cur = 0;
     int skip = 0;
@@ -274,6 +275,11 @@ static int tm2_read_stream(TM2Context *ctx, const uint8_t *buf, int stream_id) {
     if(len == 0)
         return 4;
 
+    if (len >= INT_MAX/4-1 || len < 0 || len > buf_size) {
+        av_log(ctx->avctx, AV_LOG_ERROR, "Error, invalid stream size.\n");
+        return -1;
+    }
+
     toks = AV_RB32(buf); buf += 4; cur += 4;
     if(toks & 1) {
         len = AV_RB32(buf); buf += 4; cur += 4;
@@ -313,8 +319,13 @@ static int tm2_read_stream(TM2Context *ctx, const uint8_t *buf, int stream_id) {
     len = AV_RB32(buf); buf += 4; cur += 4;
     if(len > 0) {
         init_get_bits(&ctx->gb, buf, (skip - cur) * 8);
-        for(i = 0; i < toks; i++)
+        for(i = 0; i < toks; i++) {
+            if (get_bits_left(&ctx->gb) <= 0) {
+                av_log(ctx->avctx, AV_LOG_ERROR, "Incorrect number of tokens: %i\n", toks);
+                return -1;
+            }
             ctx->tokens[stream_id][i] = tm2_get_token(&ctx->gb, &codes);
+        }
     } else {
         for(i = 0; i < toks; i++)
             ctx->tokens[stream_id][i] = codes.recode[0];
@@ -788,7 +799,7 @@ static int decode_frame(AVCodecContext *avctx,
     }
 
     for(i = 0; i < TM2_NUM_STREAMS; i++){
-        t = tm2_read_stream(l, swbuf + skip, tm2_stream_order[i]);
+        t = tm2_read_stream(l, swbuf + skip, tm2_stream_order[i], buf_size);
         if(t == -1){
             av_free(swbuf);
             return -1;