avcodec/pafvideo: Check for bitstream end in decode_0()

Fixes: Timeout
Fixes: 3529/clusterfuzz-testcase-5057068371279872

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpegSigned-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/pafvideo.c

@@ -181,6 +181,8 @@ static int decode_0(PAFVideoDecContext *c, uint8_t *pkt, uint8_t code)
             dend   = c->frame[page] + c->frame_size;
             offset = (x & 0x7F) * 2;
             j      = bytestream2_get_le16(&c->gb) + offset;
+            if (bytestream2_get_bytes_left(&c->gb) < (j - offset) * 16)
+                return AVERROR_INVALIDDATA;
             do {
                 offset++;
                 if (dst + 3 * c->width + 4 > dend)
@@ -198,7 +200,8 @@ static int decode_0(PAFVideoDecContext *c, uint8_t *pkt, uint8_t code)
     do {
         set_src_position(c, &src, &send);
         if ((src + 3 * c->width + 4 > send) ||
-            (dst + 3 * c->width + 4 > dend))
+            (dst + 3 * c->width + 4 > dend) ||
+            bytestream2_get_bytes_left(&c->gb) < 4)
             return AVERROR_INVALIDDATA;
         copy_block4(dst, src, c->width, c->width, 4);
         i++;