nsvdec: Be more careful with av_malloc().

Check results for av_malloc() and fix an overflow in one call.

Related to CVE-2011-3940.

Based in part on work from Michael Niedermayer.

Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind

libavformat/nsvdec.c

@@ -314,7 +314,9 @@ static int nsv_parse_NSVf_header(AVFormatContext *s)
         char *token, *value;
         char quote;
 
-        p = strings = av_mallocz(strings_size + 1);
+        p = strings = av_mallocz((size_t)strings_size + 1);
+        if (!p)
+            return AVERROR(ENOMEM);
         endp = strings + strings_size;
         avio_read(pb, strings, strings_size);
         while (p < endp) {
@@ -349,6 +351,8 @@ static int nsv_parse_NSVf_header(AVFormatContext *s)
         if((unsigned)table_entries_used >= UINT_MAX / sizeof(uint32_t))
             return -1;
         nsv->nsvs_file_offset = av_malloc((unsigned)table_entries_used * sizeof(uint32_t));
+        if (!nsv->nsvs_file_offset)
+            return AVERROR(ENOMEM);
 
         for(i=0;i<table_entries_used;i++)
             nsv->nsvs_file_offset[i] = avio_rl32(pb) + size;
@@ -356,6 +360,8 @@ static int nsv_parse_NSVf_header(AVFormatContext *s)
         if(table_entries > table_entries_used &&
            avio_rl32(pb) == MKTAG('T','O','C','2')) {
             nsv->nsvs_timestamps = av_malloc((unsigned)table_entries_used*sizeof(uint32_t));
+            if (!nsv->nsvs_timestamps)
+                return AVERROR(ENOMEM);
             for(i=0;i<table_entries_used;i++) {
                 nsv->nsvs_timestamps[i] = avio_rl32(pb);
             }