From f6551f822fe020843299bd807ec6989abd070b2c Mon Sep 17 00:00:00 2001
From: Even Rouault <even.rouault@spatialys.com>
Date: Sat, 29 Jul 2017 16:29:11 +0200
Subject: [PATCH] opj_t1_clbl_decode_processor(): avoid undefined behaviour if
 roishift >= 31. Fixes
 https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=2506. Credit to OSS
 Fuzz

---
 src/lib/openjp2/t1.c | 24 ++++++++++++++++--------
 1 file changed, 16 insertions(+), 8 deletions(-)

diff --git a/src/lib/openjp2/t1.c b/src/lib/openjp2/t1.c
index bd615d59..3615a0e6 100644
--- a/src/lib/openjp2/t1.c
+++ b/src/lib/openjp2/t1.c
@@ -1685,14 +1685,22 @@ static void opj_t1_clbl_decode_processor(void* user_data, opj_tls_t* tls)
     cblk_h = t1->h;
 
     if (tccp->roishift) {
-        OPJ_INT32 thresh = 1 << tccp->roishift;
-        for (j = 0; j < cblk_h; ++j) {
-            for (i = 0; i < cblk_w; ++i) {
-                OPJ_INT32 val = datap[(j * cblk_w) + i];
-                OPJ_INT32 mag = abs(val);
-                if (mag >= thresh) {
-                    mag >>= tccp->roishift;
-                    datap[(j * cblk_w) + i] = val < 0 ? -mag : mag;
+        if (tccp->roishift >= 31) {
+            for (j = 0; j < cblk_h; ++j) {
+                for (i = 0; i < cblk_w; ++i) {
+                    datap[(j * cblk_w) + i] = 0;
+                }
+            }
+        } else {
+            OPJ_INT32 thresh = 1 << tccp->roishift;
+            for (j = 0; j < cblk_h; ++j) {
+                for (i = 0; i < cblk_w; ++i) {
+                    OPJ_INT32 val = datap[(j * cblk_w) + i];
+                    OPJ_INT32 mag = abs(val);
+                    if (mag >= thresh) {
+                        mag >>= tccp->roishift;
+                        datap[(j * cblk_w) + i] = val < 0 ? -mag : mag;
+                    }
                 }
             }
         }