From 5d499272b95a6b890a1397e11d20937de000d31b Mon Sep 17 00:00:00 2001
From: Ray Johnston <ray.johnston@artifex.com>
Date: Wed, 22 Jul 2020 09:57:54 -0700
Subject: [PATCH 410/532] Bug 702582, CVE 2020-15900 Memory Corruption in
 Ghostscript 9.52

Fix the 'rsearch' calculation for the 'post' size to give the correct
size.  Previous calculation would result in a size that was too large,
and could underflow to max uint32_t. Also fix 'rsearch' to return the
correct 'pre' string with empty string match.

A future change may 'undefine' this undocumented, non-standard operator
during initialization as we do with the many other non-standard internal
PostScript operators and procedures.
---
 psi/zstring.c | 17 +++++++++++------
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/psi/zstring.c b/psi/zstring.c
index 33662da..58e1af2 100644
--- a/psi/zstring.c
+++ b/psi/zstring.c
@@ -142,13 +142,18 @@ search_impl(i_ctx_t *i_ctx_p, bool forward)
     return 0;
 found:
     op->tas.type_attrs = op1->tas.type_attrs;
-    op->value.bytes = ptr;
-    r_set_size(op, size);
+    op->value.bytes = ptr;				/* match */
+    op->tas.rsize = size;				/* match */
     push(2);
-    op[-1] = *op1;
-    r_set_size(op - 1, ptr - op[-1].value.bytes);
-    op1->value.bytes = ptr + size;
-    r_set_size(op1, count + (!forward ? (size - 1) : 0));
+    op[-1] = *op1;					/* pre */
+    op[-3].value.bytes = ptr + size;			/* post */
+    if (forward) {
+        op[-1].tas.rsize = ptr - op[-1].value.bytes;	/* pre */
+        op[-3].tas.rsize = count;			/* post */
+    } else {
+        op[-1].tas.rsize = count;			/* pre */
+        op[-3].tas.rsize -= count + size;		/* post */
+    }
     make_true(op);
     return 0;
 }
-- 
1.8.3.1

