linux-kernel - [PATCH 1/1] kernel/sysctl.c: avoid overflow

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Message-Id: <1465608788-4813-1-git-send-email-xypron.glpk@gmx.de>
Date:	Sat, 11 Jun 2016 03:33:08 +0200
From:	Heinrich Schuchardt <xypron.glpk@....de>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Kees Cook <keescook@...omium.org>,
	Don Zickus <dzickus@...hat.com>,
	Al Viro <viro@...iv.linux.org.uk>,
	Dave Young <dyoung@...hat.com>,
	Hugh Dickins <hughd@...gle.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Daniel Cashman <dcashman@...gle.com>, Willy Tarreau <w@....eu>,
	Alexei Starovoitov <ast@...mgrid.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Ilya Dryomov <idryomov@...il.com>,
	linux-kernel@...r.kernel.org,
	Heinrich Schuchardt <xypron.glpk@....de>
Subject: [PATCH 1/1] kernel/sysctl.c: avoid overflow

An undetected overflow may occur in do_proc_dointvec_minmax_conv_param.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@....de>
---
 kernel/sysctl.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 35f0dcb..a9e7be3 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -2313,7 +2313,17 @@ static int do_proc_dointvec_minmax_conv(bool *negp, unsigned long *lvalp,
 {
 	struct do_proc_dointvec_minmax_conv_param *param = data;
 	if (write) {
-		int val = *negp ? -*lvalp : *lvalp;
+		int val;
+
+		if (*negp) {
+			if (*lvalp > (unsigned long) INT_MAX + 1)
+				return -EINVAL;
+			val = -*lvalp;
+		} else {
+			if (*lvalp > (unsigned long) INT_MAX)
+				return -EINVAL;
+			val = *lvalp;
+		}
 		if ((param->min && *param->min > val) ||
 		    (param->max && *param->max < val))
 			return -EINVAL;
-- 
2.1.4