avcodec/jpeg2000: Dynamically allocate codeblock data

Fixes: OOM
Fixes: 3541/clusterfuzz-testcase-minimized-6469958596820992

Adds support for decoding codeblock data larger than 8kb
Reduces decoder memory consumption

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

libavcodec/j2kenc.c

@@ -663,7 +663,8 @@ static void encode_cblk(Jpeg2000EncoderContext *s, Jpeg2000T1Context *t1, Jpeg20
         bpno = cblk->nonzerobits - 1;
     }
 
-    ff_mqc_initenc(&t1->mqc, cblk->data);
+    cblk->data[0] = 0;
+    ff_mqc_initenc(&t1->mqc, cblk->data + 1);
 
     for (passno = 0; bpno >= 0; passno++){
         nmsedec=0;
@@ -796,7 +797,7 @@ static int encode_packet(Jpeg2000EncoderContext *s, Jpeg2000ResLevel *rlevel, in
                 if (cblk->ninclpasses){
                     if (s->buf_end - s->buf < cblk->passes[cblk->ninclpasses-1].rate)
                         return -1;
-                    bytestream_put_buffer(&s->buf, cblk->data,   cblk->passes[cblk->ninclpasses-1].rate
+                    bytestream_put_buffer(&s->buf, cblk->data + 1,   cblk->passes[cblk->ninclpasses-1].rate
                                                                - cblk->passes[cblk->ninclpasses-1].flushed_len);
                     bytestream_put_buffer(&s->buf, cblk->passes[cblk->ninclpasses-1].flushed,
                                                    cblk->passes[cblk->ninclpasses-1].flushed_len);
@@ -937,6 +938,9 @@ static int encode_tile(Jpeg2000EncoderContext *s, Jpeg2000Tile *tile, int tileno
                                 }
                             }
                         }
+                        prec->cblk[cblkno].data = av_malloc(1 + 8192);
+                        if (!prec->cblk[cblkno].data)
+                            return AVERROR(ENOMEM);
                         encode_cblk(s, &t1, prec->cblk + cblkno, tile, xx1 - xx0, yy1 - yy0,
                                     bandpos, codsty->nreslevels - reslevelno - 1);
                         xx0 = xx1;

libavcodec/jpeg2000.c

@@ -357,7 +357,6 @@ static int init_prec(Jpeg2000Band *band,
                                  comp->reslevel[reslevelno-1].coord[1][0];
         }
 
-        cblk->zero      = 0;
         cblk->lblock    = 3;
         cblk->length    = 0;
         memset(cblk->lengthinc, 0, sizeof(cblk->lengthinc));
@@ -598,11 +597,20 @@ void ff_jpeg2000_cleanup(Jpeg2000Component *comp, Jpeg2000CodingStyle *codsty)
             for (precno = 0; precno < reslevel->num_precincts_x * reslevel->num_precincts_y; precno++) {
                 if (band->prec) {
                     Jpeg2000Prec *prec = band->prec + precno;
+                    int nb_code_blocks = prec->nb_codeblocks_height * prec->nb_codeblocks_width;
+
                     av_freep(&prec->zerobits);
                     av_freep(&prec->cblkincl);
+                    if (prec->cblk) {
+                        int cblkno;
+                        for (cblkno = 0; cblkno < nb_code_blocks; cblkno ++) {
+                            Jpeg2000Cblk *cblk = &prec->cblk[cblkno];
+                            av_freep(&cblk->data);
+                        }
                         av_freep(&prec->cblk);
                     }
                 }
+            }
 
             av_freep(&band->prec);
         }

libavcodec/jpeg2000.h

@@ -168,8 +168,8 @@ typedef struct Jpeg2000Cblk {
     uint16_t lengthinc[JPEG2000_MAX_PASSES];
     uint8_t nb_lengthinc;
     uint8_t lblock;
-    uint8_t zero;
-    uint8_t data[8192];
+    uint8_t *data;
+    size_t data_allocated;
     int nb_terminations;
     int nb_terminationsinc;
     int data_start[JPEG2000_MAX_PASSES];

libavcodec/jpeg2000dec.c

@@ -1001,10 +1001,18 @@ static int jpeg2000_decode_packet(Jpeg2000DecoderContext *s, Jpeg2000Tile *tile,
 
                 if ((ret = get_bits(s, av_log2(newpasses1) + cblk->lblock)) < 0)
                     return ret;
-                if (ret > sizeof(cblk->data)) {
+                if (ret > cblk->data_allocated) {
+                    size_t new_size = FFMAX(2*cblk->data_allocated, ret);
+                    void *new = av_realloc(cblk->data, new_size);
+                    if (new) {
+                        cblk->data = new;
+                        cblk->data_allocated = new_size;
+                    }
+                }
+                if (ret > cblk->data_allocated) {
                     avpriv_request_sample(s->avctx,
                                         "Block with lengthinc greater than %"SIZE_SPECIFIER"",
-                                        sizeof(cblk->data));
+                                        cblk->data_allocated);
                     return AVERROR_PATCHWELCOME;
                 }
                 cblk->lengthinc[cblk->nb_lengthinc++] = ret;
@@ -1030,8 +1038,16 @@ static int jpeg2000_decode_packet(Jpeg2000DecoderContext *s, Jpeg2000Tile *tile,
         for (cblkno = 0; cblkno < nb_code_blocks; cblkno++) {
             Jpeg2000Cblk *cblk = prec->cblk + cblkno;
             for (cwsno = 0; cwsno < cblk->nb_lengthinc; cwsno ++) {
+                if (cblk->data_allocated < cblk->length + cblk->lengthinc[cwsno] + 4) {
+                    size_t new_size = FFMAX(2*cblk->data_allocated, cblk->length + cblk->lengthinc[cwsno] + 4);
+                    void *new = av_realloc(cblk->data, new_size);
+                    if (new) {
+                        cblk->data = new;
+                        cblk->data_allocated = new_size;
+                    }
+                }
                 if (   bytestream2_get_bytes_left(&s->g) < cblk->lengthinc[cwsno]
-                    || sizeof(cblk->data) < cblk->length + cblk->lengthinc[cwsno] + 4
+                    || cblk->data_allocated < cblk->length + cblk->lengthinc[cwsno] + 4
                 ) {
                     av_log(s->avctx, AV_LOG_ERROR,
                         "Block length %"PRIu16" or lengthinc %d is too large, left %d\n",