linux-kernel - [PATCH v2 2/3] kernel/sysctl.c: add missing range check in do_proc_dointvec_minmax

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Message-Id: <20190207123426.9202-3-zev@bewilderbeest.net>
Date:   Thu,  7 Feb 2019 06:34:25 -0600
From:   Zev Weiss <zev@...ilderbeest.net>
To:     Luis Chamberlain <mcgrof@...nel.org>,
        Kees Cook <keescook@...omium.org>
Cc:     linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>, yzaikin@...gle.com,
        brendanhiggins@...gle.com, Zev Weiss <zev@...ilderbeest.net>,
        stable@...r.kernel.org
Subject: [PATCH v2 2/3] kernel/sysctl.c: add missing range check in do_proc_dointvec_minmax_conv

This bug has apparently existed since the introduction of this function
in the pre-git era (4500e91754d3 in Thomas Gleixner's history.git,
"[NET]: Add proc_dointvec_userhz_jiffies, use it for proper handling of
neighbour sysctls.").  As a minimal fix we can simply duplicate the
corresponding check in do_proc_dointvec_conv().

Cc: <stable@...r.kernel.org> # v2.6.2+
Signed-off-by: Zev Weiss <zev@...ilderbeest.net>
---
 kernel/sysctl.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 5fc724e4e454..a71c4b3935bc 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -2564,7 +2564,16 @@ 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;
-- 
2.20.1