This fixes a null pointer dereference in MuJS regexp.c as
reported at:

http://seclists.org/oss-sec/2017/q1/74

Patch lifted from upstream source repository:

http://git.ghostscript.com/?p=mujs.git;h=fd003eceda531e13fbdd1aeb6e9c73156496e569

From fd003eceda531e13fbdd1aeb6e9c73156496e569 Mon Sep 17 00:00:00 2001
From: Tor Andersson <tor@ccxvii.net>
Date: Fri, 2 Dec 2016 14:56:20 -0500
Subject: [PATCH] Fix 697381: check allocation when compiling regular
 expressions.

Also use allocator callback function.
---
 thirdparty/mujs/jsgc.c     |  2 +-
 thirdparty/mujs/jsregexp.c |  2 +-
 thirdparty/mujs/jsstate.c  |  6 ------
 thirdparty/mujs/regexp.c   | 45 +++++++++++++++++++++++++++++++++++----------
 thirdparty/mujs/regexp.h   |  7 +++++++
 5 files changed, 44 insertions(+), 18 deletions(-)

diff --git a/thirdparty/mujs/jsgc.c b/thirdparty/mujs/jsgc.c
index 4f7e7dc..f80111e 100644
--- a/thirdparty/mujs/jsgc.c
+++ b/thirdparty/mujs/jsgc.c
@@ -46,7 +46,7 @@ static void jsG_freeobject(js_State *J, js_Object *obj)
 		jsG_freeproperty(J, obj->head);
 	if (obj->type == JS_CREGEXP) {
 		js_free(J, obj->u.r.source);
-		js_regfree(obj->u.r.prog);
+		js_regfreex(J->alloc, J->actx, obj->u.r.prog);
 	}
 	if (obj->type == JS_CITERATOR)
 		jsG_freeiterator(J, obj->u.iter.head);
diff --git a/thirdparty/mujs/jsregexp.c b/thirdparty/mujs/jsregexp.c
index a2d5156..7b09c06 100644
--- a/thirdparty/mujs/jsregexp.c
+++ b/thirdparty/mujs/jsregexp.c
@@ -16,7 +16,7 @@ void js_newregexp(js_State *J, const char *pattern, int flags)
 	if (flags & JS_REGEXP_I) opts |= REG_ICASE;
 	if (flags & JS_REGEXP_M) opts |= REG_NEWLINE;
 
-	prog = js_regcomp(pattern, opts, &error);
+	prog = js_regcompx(J->alloc, J->actx, pattern, opts, &error);
 	if (!prog)
 		js_syntaxerror(J, "regular expression: %s", error);
 
diff --git a/thirdparty/mujs/jsstate.c b/thirdparty/mujs/jsstate.c
index 638cab3..fd5bcf6 100644
--- a/thirdparty/mujs/jsstate.c
+++ b/thirdparty/mujs/jsstate.c
@@ -9,12 +9,6 @@
 
 static void *js_defaultalloc(void *actx, void *ptr, int size)
 {
-	if (size == 0) {
-		free(ptr);
-		return NULL;
-	}
-	if (!ptr)
-		return malloc((size_t)size);
 	return realloc(ptr, (size_t)size);
 }
 
diff --git a/thirdparty/mujs/regexp.c b/thirdparty/mujs/regexp.c
index 9852be2..01c18a3 100644
--- a/thirdparty/mujs/regexp.c
+++ b/thirdparty/mujs/regexp.c
@@ -807,23 +807,31 @@ static void dumpprog(Reprog *prog)
 }
 #endif
 
-Reprog *regcomp(const char *pattern, int cflags, const char **errorp)
+Reprog *regcompx(void *(*alloc)(void *ctx, void *p, int n), void *ctx,
+	const char *pattern, int cflags, const char **errorp)
 {
 	struct cstate g;
 	Renode *node;
 	Reinst *split, *jump;
 	int i;
 
-	g.prog = malloc(sizeof (Reprog));
-	g.pstart = g.pend = malloc(sizeof (Renode) * strlen(pattern) * 2);
+	g.pstart = NULL;
+	g.prog = NULL;
 
 	if (setjmp(g.kaboom)) {
 		if (errorp) *errorp = g.error;
-		free(g.pstart);
-		free(g.prog);
+		alloc(ctx, g.pstart, 0);
+		alloc(ctx, g.prog, 0);
 		return NULL;
 	}
 
+	g.prog = alloc(ctx, NULL, sizeof (Reprog));
+	if (!g.prog)
+		die(&g, "cannot allocate regular expression");
+	g.pstart = g.pend = alloc(ctx, NULL, sizeof (Renode) * strlen(pattern) * 2);
+	if (!g.pstart)
+		die(&g, "cannot allocate regular expression parse list");
+
 	g.source = pattern;
 	g.ncclass = 0;
 	g.nsub = 1;
@@ -840,7 +848,9 @@ Reprog *regcomp(const char *pattern, int cflags, const char **errorp)
 		die(&g, "syntax error");
 
 	g.prog->nsub = g.nsub;
-	g.prog->start = g.prog->end = malloc((count(node) + 6) * sizeof (Reinst));
+	g.prog->start = g.prog->end = alloc(ctx, NULL, (count(node) + 6) * sizeof (Reinst));
+	if (!g.prog->start)
+		die(&g, "cannot allocate regular expression instruction list");
 
 	split = emit(g.prog, I_SPLIT);
 	split->x = split + 3;
@@ -859,20 +869,35 @@ Reprog *regcomp(const char *pattern, int cflags, const char **errorp)
 	dumpprog(g.prog);
 #endif
 
-	free(g.pstart);
+	alloc(ctx, g.pstart, 0);
 
 	if (errorp) *errorp = NULL;
 	return g.prog;
 }
 
-void regfree(Reprog *prog)
+void regfreex(void *(*alloc)(void *ctx, void *p, int n), void *ctx, Reprog *prog)
 {
 	if (prog) {
-		free(prog->start);
-		free(prog);
+		alloc(ctx, prog->start, 0);
+		alloc(ctx, prog, 0);
 	}
 }
 
+static void *default_alloc(void *ctx, void *p, int n)
+{
+	return realloc(p, (size_t)n);
+}
+
+Reprog *regcomp(const char *pattern, int cflags, const char **errorp)
+{
+	return regcompx(default_alloc, NULL, pattern, cflags, errorp);
+}
+
+void regfree(Reprog *prog)
+{
+	regfreex(default_alloc, NULL, prog);
+}
+
 /* Match */
 
 static int isnewline(int c)
diff --git a/thirdparty/mujs/regexp.h b/thirdparty/mujs/regexp.h
index 4bb4615..6bb73e8 100644
--- a/thirdparty/mujs/regexp.h
+++ b/thirdparty/mujs/regexp.h
@@ -1,6 +1,8 @@
 #ifndef regexp_h
 #define regexp_h
 
+#define regcompx js_regcompx
+#define regfreex js_regfreex
 #define regcomp js_regcomp
 #define regexec js_regexec
 #define regfree js_regfree
@@ -8,6 +10,11 @@
 typedef struct Reprog Reprog;
 typedef struct Resub Resub;
 
+Reprog *regcompx(void *(*alloc)(void *ctx, void *p, int n), void *ctx,
+	const char *pattern, int cflags, const char **errorp);
+void regfreex(void *(*alloc)(void *ctx, void *p, int n), void *ctx,
+	Reprog *prog);
+
 Reprog *regcomp(const char *pattern, int cflags, const char **errorp);
 int regexec(Reprog *prog, const char *string, Resub *sub, int eflags);
 void regfree(Reprog *prog);
-- 
2.9.1