linux-kernel - [PATCH] simple_strtoul: prevent integer overflows

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Date:	Thu, 5 May 2011 01:54:41 -0400
From:	Mansour Moufid <mansourmoufid@...il.com>
To:	torvalds@...ux-foundation.org
Cc:	linux-kernel@...r.kernel.org
Subject: [PATCH] simple_strtoul: prevent integer overflows

From: Mansour Moufid <mansourmoufid@...il.com>

This patch prevents integer overflows in the functions
`simple_strtoull' and `simple_strtoul', in the file lib/vsprintf.c.
This applies to stable version 2.6.38.5.

I'm aware of the kstrto* functions, but simple_strto* are still used
in some network-exposed code (netfilter).

Signed-off-by: Mansour Moufid <mansourmoufid@...il.com>
---
--- vsprintf.c.orig	2011-05-04 22:00:07.000000000 -0400
+++ vsprintf.c	2011-05-04 22:27:45.000000000 -0400
@@ -63,11 +63,20 @@ unsigned long long simple_strtoull(const
 		cp += 2;

 	while (isxdigit(*cp)) {
-		unsigned int value;
+		unsigned int value = 0;

-		value = isdigit(*cp) ? *cp - '0' : TOLOWER(*cp) - 'a' + 10;
+		if (isdigit(*cp))
+			value = *cp - '0';
+		else if (isalpha(*cp))
+			value = TOLOWER(*cp) - 'a' + 10;
+		else
+			break;
 		if (value >= base)
 			break;
+		if (result > (ULLONG_MAX - value) / base) {
+			result = ULLONG_MAX;
+			break;
+		}
 		result = result * base + value;
 		cp++;
 	}
@@ -86,7 +95,12 @@ EXPORT_SYMBOL(simple_strtoull);
  */
 unsigned long simple_strtoul(const char *cp, char **endp, unsigned int base)
 {
-	return simple_strtoull(cp, endp, base);
+	unsigned long long result = simple_strtoull(cp, endp, base);
+
+	if (result <= ULONG_MAX)
+		return result;
+
+	return ULONG_MAX;
 }
 EXPORT_SYMBOL(simple_strtoul);
--
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