avcodec/jpeg2000dec: Check precno before using it in JPEG2000_PGOD_CPRL

Fixes out of array reads
Fixes: asan_heap-oob_f0de57_6823_mjp2.mov

Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/jpeg2000dec.c

@@ -889,6 +889,10 @@ static int jpeg2000_decode_packets(Jpeg2000DecoderContext *s, Jpeg2000Tile *tile
                         prcx   = ff_jpeg2000_ceildivpow2(x, reducedresno) >> rlevel->log2_prec_width;
                         prcy   = ff_jpeg2000_ceildivpow2(y, reducedresno) >> rlevel->log2_prec_height;
                         precno = prcx + rlevel->num_precincts_x * prcy;
+
+                        if (prcx >= rlevel->num_precincts_x || prcy >= rlevel->num_precincts_y)
+                            return AVERROR_PATCHWELCOME;
+
                         for (layno = 0; layno < tile->codsty[0].nlayers; layno++) {
                             if ((ret = jpeg2000_decode_packet(s, codsty, rlevel,
                                                               precno, layno,