avformat/flvdec: Check for avio_read() failure in amf_get_string()

Suggested-by: Anton Khirnov <anton@khirnov.net>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavformat/flvdec.c

@@ -384,13 +384,18 @@ static int flv_set_video_codec(AVFormatContext *s, AVStream *vstream,
 
 static int amf_get_string(AVIOContext *ioc, char *buffer, int buffsize)
 {
+    int ret;
     int length = avio_rb16(ioc);
     if (length >= buffsize) {
         avio_skip(ioc, length);
         return -1;
     }
 
-    avio_read(ioc, buffer, length);
+    ret = avio_read(ioc, buffer, length);
+    if (ret < 0)
+        return ret;
+    if (ret < length)
+        return AVERROR_INVALIDDATA;
 
     buffer[length] = '\0';