avcodec/h2645_parse: Use av_fast_realloc() for nals array

Fixes: Timeout (17sec ->281ms)
Fixes: 17833/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_H264_fuzzer-5638346914660352

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

libavcodec/h2645_parse.c

@@ -455,8 +455,12 @@ int ff_h2645_packet_split(H2645Packet *pkt, const uint8_t *buf, int length,
 
         if (pkt->nals_allocated < pkt->nb_nals + 1) {
             int new_size = pkt->nals_allocated + 1;
-            void *tmp = av_realloc_array(pkt->nals, new_size, sizeof(*pkt->nals));
+            void *tmp;
 
+            if (new_size >= INT_MAX / sizeof(*pkt->nals))
+                return AVERROR(ENOMEM);
+
+            tmp = av_fast_realloc(pkt->nals, &pkt->nal_buffer_size, new_size * sizeof(*pkt->nals));
             if (!tmp)
                 return AVERROR(ENOMEM);
 

libavcodec/h2645_parse.h

@@ -78,6 +78,7 @@ typedef struct H2645Packet {
     H2645RBSP rbsp;
     int nb_nals;
     int nals_allocated;
+    unsigned nal_buffer_size;
 } H2645Packet;
 
 /**