From 24ddcfc7e37c0ce3b0f1852042ee431a53fd774c 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 22e21ef..f036cef 100644
--- a/jbig2_image.c
+++ b/jbig2_image.c
@@ -34,6 +34,10 @@
 #define INT32_MAX  0x7fffffff
 #endif
 
+#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)
@@ -255,6 +259,15 @@ 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 (src == NULL)
         return 0;
 
-- 
2.26.2