avformat/rsd: reject short ADPCM_THP extradata reads

Use ffio_read_size() to enforce exact-length reads of the per-channel
ADPCM_THP coefficient tables. Previously the return value of
avio_read() was unchecked, silently accepting truncated extradata.

(cherry picked from commit 06d19d000d)
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavformat/rsd.c

@@ -22,6 +22,7 @@
 #include "libavutil/intreadwrite.h"
 #include "avformat.h"
 #include "avio.h"
+#include "avio_internal.h"
 #include "demux.h"
 #include "internal.h"
 
@@ -131,9 +132,9 @@ static int rsd_read_header(AVFormatContext *s)
             return ret;
 
         for (i = 0; i < par->ch_layout.nb_channels; i++) {
-            if (avio_feof(pb))
-                return AVERROR_EOF;
-            avio_read(s->pb, st->codecpar->extradata + 32 * i, 32);
+            ret = ffio_read_size(s->pb, st->codecpar->extradata + 32 * i, 32);
+            if (ret < 0)
+                return ret;
             avio_skip(s->pb, 8);
         }
         break;