From fa3d30fd18c348bb4b1f3858fb860f4fcd4b2045 Mon Sep 17 00:00:00 2001
From: Tor Andersson <tor.andersson@gmail.com>
Date: Thu, 12 Jan 2017 15:13:14 +0100
Subject: [PATCH] Fix 697448: Limit the maximum program size to something
 reasonable.

A regular expression with lots of nested repetition can lead to
integer overflow when calculating the size of the program.

Check max program size when counting the number of instructions required
for a loop, so we can bail before integer overflow can happen.
---
 regexp.c | 38 ++++++++++++++++++++++++--------------
 1 file changed, 24 insertions(+), 14 deletions(-)

diff --git a/regexp.c b/regexp.c
index 01c18a3..4a5948b 100644
--- a/regexp.c
+++ b/regexp.c
@@ -16,6 +16,7 @@
 #define REPINF 255
 #define MAXTHREAD 1000
 #define MAXSUB REG_MAXSUB
+#define MAXPROG (32 << 10)
 
 typedef struct Reclass Reclass;
 typedef struct Renode Renode;
@@ -595,23 +596,25 @@ struct Reinst {
 	Reinst *y;
 };
 
-static int count(Renode *node)
+static int count(struct cstate *g, Renode *node)
 {
-	int min, max;
+	int min, max, n;
 	if (!node) return 0;
 	switch (node->type) {
 	default: return 1;
-	case P_CAT: return count(node->x) + count(node->y);
-	case P_ALT: return count(node->x) + count(node->y) + 2;
+	case P_CAT: return count(g, node->x) + count(g, node->y);
+	case P_ALT: return count(g, node->x) + count(g, node->y) + 2;
 	case P_REP:
 		min = node->m;
 		max = node->n;
-		if (min == max) return count(node->x) * min;
-		if (max < REPINF) return count(node->x) * max + (max - min);
-		return count(node->x) * (min + 1) + 2;
-	case P_PAR: return count(node->x) + 2;
-	case P_PLA: return count(node->x) + 2;
-	case P_NLA: return count(node->x) + 2;
+		if (min == max) n = count(g, node->x) * min;
+		else if (max < REPINF) n = count(g, node->x) * max + (max - min);
+		else n = count(g, node->x) * (min + 1) + 2;
+		if (n < 0 || n > MAXPROG) die(g, "program too large");
+		return n;
+	case P_PAR: return count(g, node->x) + 2;
+	case P_PLA: return count(g, node->x) + 2;
+	case P_NLA: return count(g, node->x) + 2;
 	}
 }
 
@@ -813,7 +816,7 @@ Reprog *regcompx(void *(*alloc)(void *ctx, void *p, int n), void *ctx,
 	struct cstate g;
 	Renode *node;
 	Reinst *split, *jump;
-	int i;
+	int i, n;
 
 	g.pstart = NULL;
 	g.prog = NULL;
@@ -847,8 +850,17 @@ Reprog *regcompx(void *(*alloc)(void *ctx, void *p, int n), void *ctx,
 	if (g.lookahead != 0)
 		die(&g, "syntax error");
 
+#ifdef TEST
+	dumpnode(node);
+	putchar('\n');
+#endif
+
+	n = 6 + count(&g, node);
+	if (n < 0 || n > MAXPROG)
+		die(&g, "program too large");
+
 	g.prog->nsub = g.nsub;
-	g.prog->start = g.prog->end = alloc(ctx, NULL, (count(node) + 6) * sizeof (Reinst));
+	g.prog->start = g.prog->end = alloc(ctx, NULL, n * sizeof (Reinst));
 	if (!g.prog->start)
 		die(&g, "cannot allocate regular expression instruction list");
 
@@ -864,8 +876,6 @@ Reprog *regcompx(void *(*alloc)(void *ctx, void *p, int n), void *ctx,
 	emit(g.prog, I_END);
 
 #ifdef TEST
-	dumpnode(node);
-	putchar('\n');
 	dumpprog(g.prog);
 #endif
 
-- 
2.9.1