linux-kernel - [CFT][PATCH 3/3] userns: Unbreak the unprivileged remount tests

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Message-ID: <87r3whx0a8.fsf_-_@x220.int.ebiederm.org>
Date:	Tue, 02 Dec 2014 14:30:07 -0600
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Andy Lutomirski <luto@...capital.net>
Cc:	Linux Containers <containers@...ts.linux-foundation.org>,
	Josh Triplett <josh@...htriplett.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Kees Cook <keescook@...omium.org>,
	Michael Kerrisk-manpages <mtk.manpages@...il.com>,
	Linux API <linux-api@...r.kernel.org>,
	linux-man <linux-man@...r.kernel.org>,
	"linux-kernel\@vger.kernel.org" <linux-kernel@...r.kernel.org>,
	LSM <linux-security-module@...r.kernel.org>,
	Casey Schaufler <casey@...aufler-ca.com>,
	"Serge E. Hallyn" <serge@...lyn.com>,
	Richard Weinberger <richard@....at>,
	Kenton Varda <kenton@...dstorm.io>,
	stable <stable@...r.kernel.org>
Subject: [CFT][PATCH 3/3] userns: Unbreak the unprivileged remount tests


A security fix in caused the way the unprivileged remount tests were
using user namespaces to break.  Tweak the way user namespaces are
being used so the test works again.

Cc: stable@...r.kernel.org
Signed-off-by: "Eric W. Biederman" <ebiederm@...ssion.com>
---

This is what it takes to fix a broken application, in it's full glory.
This fix works even if new functionality does not exist.

 tools/testing/selftests/mount/unprivileged-remount-test.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/tools/testing/selftests/mount/unprivileged-remount-test.c b/tools/testing/selftests/mount/unprivileged-remount-test.c
index 9669d375625a..d47227494137 100644
--- a/tools/testing/selftests/mount/unprivileged-remount-test.c
+++ b/tools/testing/selftests/mount/unprivileged-remount-test.c
@@ -144,13 +144,12 @@ static void create_and_enter_userns(void)
 			strerror(errno));
 	}
 
+	if (access("/proc/self/setgroups", F_OK) == 0) {
+		write_file("/proc/self/setgroups", "0");
+	}
 	write_file("/proc/self/uid_map", "0 %d 1", uid);
 	write_file("/proc/self/gid_map", "0 %d 1", gid);
 
-	if (setgroups(0, NULL) != 0) {
-		die("setgroups failed: %s\n",
-			strerror(errno));
-	}
 	if (setgid(0) != 0) {
 		die ("setgid(0) failed %s\n",
 			strerror(errno));
-- 
1.9.1

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