[FFmpeg-cvslog] avcodec/jpeg2000htdec: Check magp before using it in a shift

[Michael Niedermayer]

ffmpeg | branch: master | Michael Niedermayer <michael at niedermayer.cc> | Wed Mar 20 03:27:13 2024 +0100| [19ad05e9e0f045b13de8de7300ca3bd34ea8ca53] | committer: Michael Niedermayer

avcodec/jpeg2000htdec: Check magp before using it in a shift

Fixes: shift exponent -1 is negative
Fixes: 65378/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_JPEG2000_fuzzer-5457678193197056

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

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=19ad05e9e0f045b13de8de7300ca3bd34ea8ca53
---

 libavcodec/jpeg2000dec.c | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/libavcodec/jpeg2000dec.c b/libavcodec/jpeg2000dec.c
index 857379da2d..28bf6be2fe 100644
--- a/libavcodec/jpeg2000dec.c
+++ b/libavcodec/jpeg2000dec.c
@@ -1886,7 +1886,7 @@ static inline void roi_scale_cblk(Jpeg2000Cblk *cblk,
     }
 }
 
-static inline void tile_codeblocks(const Jpeg2000DecoderContext *s, Jpeg2000Tile *tile)
+static inline int tile_codeblocks(const Jpeg2000DecoderContext *s, Jpeg2000Tile *tile)
 {
     Jpeg2000T1Context t1;
 
@@ -1911,6 +1911,8 @@ static inline void tile_codeblocks(const Jpeg2000DecoderContext *s, Jpeg2000Tile
                 int nb_precincts, precno;
                 Jpeg2000Band *band = rlevel->band + bandno;
                 int cblkno = 0, bandpos;
+                /* See Rec. ITU-T T.800, Equation E-2 */
+                int magp = quantsty->expn[subbandno] + quantsty->nguardbits - 1;
 
                 bandpos = bandno + (reslevelno > 0);
 
@@ -1918,6 +1920,11 @@ static inline void tile_codeblocks(const Jpeg2000DecoderContext *s, Jpeg2000Tile
                     band->coord[1][0] == band->coord[1][1])
                     continue;
 
+                if ((codsty->cblk_style & JPEG2000_CTSY_HTJ2K_F) && magp >= 31) {
+                    avpriv_request_sample(s->avctx, "JPEG2000_CTSY_HTJ2K_F and magp >= 31");
+                    return AVERROR_PATCHWELCOME;
+                }
+
                 nb_precincts = rlevel->num_precincts_x * rlevel->num_precincts_y;
                 /* Loop on precincts */
                 for (precno = 0; precno < nb_precincts; precno++) {
@@ -1928,8 +1935,6 @@ static inline void tile_codeblocks(const Jpeg2000DecoderContext *s, Jpeg2000Tile
                          cblkno < prec->nb_codeblocks_width * prec->nb_codeblocks_height;
                          cblkno++) {
                         int x, y, ret;
-                        /* See Rec. ITU-T T.800, Equation E-2 */
-                        int magp = quantsty->expn[subbandno] + quantsty->nguardbits - 1;
 
                         Jpeg2000Cblk *cblk = prec->cblk + cblkno;
 
@@ -1969,6 +1974,7 @@ static inline void tile_codeblocks(const Jpeg2000DecoderContext *s, Jpeg2000Tile
             ff_dwt_decode(&comp->dwt, codsty->transform == FF_DWT97 ? (void*)comp->f_data : (void*)comp->i_data);
 
     } /*end comp */
+    return 0;
 }
 
 #define WRITE_FRAME(D, PIXEL)                                                                     \
@@ -2045,7 +2051,9 @@ static int jpeg2000_decode_tile(AVCodecContext *avctx, void *td,
     AVFrame *picture = td;
     Jpeg2000Tile *tile = s->tile + jobnr;
 
-    tile_codeblocks(s, tile);
+    int ret = tile_codeblocks(s, tile);
+    if (ret < 0)
+        return ret;
 
     /* inverse MCT transformation */
     if (tile->codsty[0].mct)