From df29c989c7578476921d4f5ec277ee3cc9e87350 Mon Sep 17 00:00:00 2001
From: Robin Watts <Robin.Watts@artifex.com>
Date: Mon, 27 Jan 2020 10:12:24 -0800
Subject: [PATCH] Fix OSS-Fuzz issue 20332: buffer overflow in
 jbig2_image_compose.

With extreme values of x/y/w/h we can get overflow. Test for this
and exit safely.

Thanks for OSS-Fuzz for reporting.
---
 jbig2_image.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/jbig2_image.c b/jbig2_image.c
index 23e12ae..74050b9 100644
--- a/jbig2_image.c
+++ b/jbig2_image.c
@@ -30,6 +30,10 @@
 #include "jbig2_priv.h"
 #include "jbig2_image.h"
 
+#if !defined (UINT32_MAX)
+#define UINT32_MAX  0xffffffffu
+#endif
+
 /* allocate a Jbig2Image structure and its associated bitmap */
 Jbig2Image *
 jbig2_image_new(Jbig2Ctx *ctx, uint32_t width, uint32_t height)
@@ -229,6 +233,15 @@ jbig2_image_compose(Jbig2Ctx *ctx, Jbig2Image *dst, Jbig2Image *src, int x, int
     uint8_t *d, *dd;
     uint8_t mask, rightmask;
 
+    if ((UINT32_MAX - src->width  < (x > 0 ? x : -x)) ||
+        (UINT32_MAX - src->height < (y > 0 ? y : -y)))
+    {
+#ifdef JBIG2_DEBUG
+        jbig2_error(ctx, JBIG2_SEVERITY_DEBUG, -1, "overflow in compose_image");
+#endif
+        return 0;
+    }
+
     if (op != JBIG2_COMPOSE_OR) {
         /* hand off the the general routine */
         return jbig2_image_compose_unopt(ctx, dst, src, x, y, op);
-- 
2.26.2