MFC r278739:

Disallow pattern spaces which would cause intermediate calculations to
overflow size_t.

Obtained from:	DragonFly (2841837793bd095a82f477e9c370cfe6cfb3862c dillon)
Security:	CERT VU#695940

1 files changed, 17 insertions, 0 deletions

diff --git a/lib/libc/regex/regcomp.c b/lib/libc/regex/regcomp.c
index 2ecb88c..ae92f6a 100644
--- a/lib/libc/regex/regcomp.c
+++ b/lib/libc/regex/regcomp.c
@@ -192,6 +192,7 @@ regcomp(regex_t * __restrict preg,
 	struct parse *p = &pa;
 	int i;
 	size_t len;
+	size_t maxlen;
 #ifdef REDEBUG
 #	define	GOODFLAGS(f)	(f)
 #else
@@ -213,7 +214,23 @@ regcomp(regex_t * __restrict preg,
 	g = (struct re_guts *)malloc(sizeof(struct re_guts));
 	if (g == NULL)
 		return(REG_ESPACE);
+	/*
+	 * Limit the pattern space to avoid a 32-bit overflow on buffer
+	 * extension.  Also avoid any signed overflow in case of conversion
+	 * so make the real limit based on a 31-bit overflow.
+	 *
+	 * Likely not applicable on 64-bit systems but handle the case
+	 * generically (who are we to stop people from using ~715MB+
+	 * patterns?).
+	 */
+	maxlen = ((size_t)-1 >> 1) / sizeof(sop) * 2 / 3;
+	if (len >= maxlen) {
+		free((char *)g);
+		return(REG_ESPACE);
+	}
 	p->ssize = len/(size_t)2*(size_t)3 + (size_t)1;	/* ugh */
+	assert(p->ssize >= len);
+
 	p->strip = (sop *)malloc(p->ssize * sizeof(sop));
 	p->slen = 0;
 	if (p->strip == NULL) {