linux-kernel - [PATCH 2/3] sysctl: detect overflows in proc_get

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Date:	Sun, 29 Mar 2015 21:28:28 +0200
From:	Heinrich Schuchardt <xypron.glpk@....de>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Michal Nazarewicz <mina86@...a86.com>,
	Ingo Molnar <mingo@...nel.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Joe Perches <joe@...ches.com>, Josh Hunt <johunt@...mai.com>,
	Rasmus Villemoes <linux@...musvillemoes.dk>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Daniel Walter <dwalter@...gle.com>,
	David Rientjes <rientjes@...gle.com>,
	Kees Cook <keescook@...omium.org>,
	"David S. Miller" <davem@...emloft.net>,
	Johannes Weiner <hannes@...xchg.org>,
	Aaron Tomlin <atomlin@...hat.com>,
	Prarit Bhargava <prarit@...hat.com>,
	Eric B Munson <emunson@...mai.com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Sam Ravnborg <sam@...nborg.org>, linux-kernel@...r.kernel.org,
	Heinrich Schuchardt <xypron.glpk@....de>
Subject: [PATCH 2/3] sysctl: detect overflows in proc_get_long

When converting strings to unsigned long overflows may occur.
These currently are not detected.

E.g. on a 32bit system
echo 0x800001234 > /proc/sys/kernel/threads-max
has the same effect as
echo 0x1234 > /proc/sys/kernel/threads-max

The patch replaces the call to deprecated simple_strtoul by a call
to kstrtoul_e.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@....de>
---
 kernel/sysctl.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 88ea2d6..4d9d139 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -1884,7 +1884,8 @@ static int proc_get_long(char **buf, size_t *size,
 	if (!isdigit(*p))
 		return -EINVAL;
 
-	*val = simple_strtoul(p, &p, 0);
+	if (kstrtoul_e(p, &p, 0, val) < 0)
+		return -EINVAL;
 
 	len = p - tmp;
 
-- 
2.1.4

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