linux-kernel - [PATCH AUTOSEL 4.19 003/141] sysctl: return -EINVAL if val violates minmax

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Message-Id: <20190601132158.25821-3-sashal@kernel.org>
Date:   Sat,  1 Jun 2019 09:19:39 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Christian Brauner <christian@...uner.io>,
        Luis Chamberlain <mcgrof@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        Alexey Dobriyan <adobriyan@...il.com>,
        Al Viro <viro@...iv.linux.org.uk>,
        Dominik Brodowski <linux@...inikbrodowski.net>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        Joe Lawrence <joe.lawrence@...hat.com>,
        Waiman Long <longman@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Sasha Levin <sashal@...nel.org>, linux-fsdevel@...r.kernel.org
Subject: [PATCH AUTOSEL 4.19 003/141] sysctl: return -EINVAL if val violates minmax

From: Christian Brauner <christian@...uner.io>

[ Upstream commit e260ad01f0aa9e96b5386d5cd7184afd949dc457 ]

Currently when userspace gives us a values that overflow e.g.  file-max
and other callers of __do_proc_doulongvec_minmax() we simply ignore the
new value and leave the current value untouched.

This can be problematic as it gives the illusion that the limit has
indeed be bumped when in fact it failed.  This commit makes sure to
return EINVAL when an overflow is detected.  Please note that this is a
userspace facing change.

Link: http://lkml.kernel.org/r/20190210203943.8227-4-christian@brauner.io
Signed-off-by: Christian Brauner <christian@...uner.io>
Acked-by: Luis Chamberlain <mcgrof@...nel.org>
Cc: Kees Cook <keescook@...omium.org>
Cc: Alexey Dobriyan <adobriyan@...il.com>
Cc: Al Viro <viro@...iv.linux.org.uk>
Cc: Dominik Brodowski <linux@...inikbrodowski.net>
Cc: "Eric W. Biederman" <ebiederm@...ssion.com>
Cc: Joe Lawrence <joe.lawrence@...hat.com>
Cc: Waiman Long <longman@...hat.com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 kernel/sysctl.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 9a85c7ae73621..f8576509c7bef 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -2791,8 +2791,10 @@ static int __do_proc_doulongvec_minmax(void *data, struct ctl_table *table, int
 			if (neg)
 				continue;
 			val = convmul * val / convdiv;
-			if ((min && val < *min) || (max && val > *max))
-				continue;
+			if ((min && val < *min) || (max && val > *max)) {
+				err = -EINVAL;
+				break;
+			}
 			*i = val;
 		} else {
 			val = convdiv * (*i) / convmul;
-- 
2.20.1