swf: check return values for av_get/new_packet().

Prevents crashers when using the packet if allocation failed.

Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
CC: libav-stable@libav.org

libavformat/swfdec.c

@@ -84,7 +84,7 @@ static int swf_read_packet(AVFormatContext *s, AVPacket *pkt)
     SWFContext *swf = s->priv_data;
     AVIOContext *pb = s->pb;
     AVStream *vst = NULL, *ast = NULL, *st = 0;
-    int tag, len, i, frame, v;
+    int tag, len, i, frame, v, res;
 
     for(;;) {
         uint64_t pos = avio_tell(pb);
@@ -147,7 +147,8 @@ static int swf_read_packet(AVFormatContext *s, AVPacket *pkt)
                 st = s->streams[i];
                 if (st->codec->codec_type == AVMEDIA_TYPE_VIDEO && st->id == ch_id) {
                     frame = avio_rl16(pb);
-                    av_get_packet(pb, pkt, len-2);
+                    if ((res = av_get_packet(pb, pkt, len-2)) < 0)
+                        return res;
                     pkt->pos = pos;
                     pkt->pts = frame;
                     pkt->stream_index = st->index;
@@ -160,9 +161,11 @@ static int swf_read_packet(AVFormatContext *s, AVPacket *pkt)
                 if (st->codec->codec_type == AVMEDIA_TYPE_AUDIO && st->id == -1) {
             if (st->codec->codec_id == CODEC_ID_MP3) {
                 avio_skip(pb, 4);
-                av_get_packet(pb, pkt, len-4);
+                if ((res = av_get_packet(pb, pkt, len-4)) < 0)
+                    return res;
             } else { // ADPCM, PCM
-                av_get_packet(pb, pkt, len);
+                if ((res = av_get_packet(pb, pkt, len)) < 0)
+                    return res;
             }
             pkt->pos = pos;
             pkt->stream_index = st->index;
@@ -187,7 +190,8 @@ static int swf_read_packet(AVFormatContext *s, AVPacket *pkt)
                 st = vst;
             }
             avio_rl16(pb); /* BITMAP_ID */
-            av_new_packet(pkt, len-2);
+            if ((res = av_new_packet(pkt, len-2)) < 0)
+                return res;
             avio_read(pb, pkt->data, 4);
             if (AV_RB32(pkt->data) == 0xffd8ffd9 ||
                 AV_RB32(pkt->data) == 0xffd9ffd8) {