[PATCH] selftests/capabilities: Fix the test_execve test

* [PATCH] selftests/capabilities: Fix the test_execve test
@ 2017-06-29 15:46 Andy Lutomirski
  2017-06-29 16:32 ` Eric W. Biederman
  2017-06-29 16:55 ` Greg KH
  0 siblings, 2 replies; 4+ messages in thread
From: Andy Lutomirski @ 2017-06-29 15:46 UTC (permalink / raw)
  To: Naresh Kamboju, Shuah Khan
  Cc: Andy Lutomirski, stable, Eric W. Biederman, Kees Cook, Greg KH,
	linux-kselftest

test_execve does rather odd mount manipulations to safely create
temporary setuid and setgid executables that aren't visible to the
rest of the system.  Those executables end up in the test's cwd, but
that cwd is MNT_DETACHed.

The core namespace code considers MNT_DETACHed trees to belong to no
mount namespace at all and, in general, MNT_DETACHed trees are only
barely function.  This interacted with commit 380cf5ba6b0a ("fs:
Treat foreign mounts as nosuid") to cause all MNT_DETACHed trees to
act as though they're nosuid, breaking the test.

Fix it by just not detaching the tree.  It's still in a private
mount namespace and is therefore still invisible to the rest of the
system (except via /proc, and the same nosuid logic will protect all
other programs on the system from believing in test_execve's setuid
bits).

While we're at it, fix some blatant whitespace problems.

Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org>
Fixes: 380cf5ba6b0a ("fs: Treat foreign mounts as nosuid")
Cc: stable@vger.kernel.org
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Shuah Khan <shuahkh@osg.samsung.com>
Cc: Greg KH <greg@kroah.com>
Cc: linux-kselftest@vger.kernel.org
Signed-off-by: Andy Lutomirski <luto@kernel.org>
---
 tools/testing/selftests/capabilities/test_execve.c | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/tools/testing/selftests/capabilities/test_execve.c b/tools/testing/selftests/capabilities/test_execve.c
index 10a21a958aaf..763f37fecfb8 100644
--- a/tools/testing/selftests/capabilities/test_execve.c
+++ b/tools/testing/selftests/capabilities/test_execve.c
@@ -138,9 +138,6 @@ static void chdir_to_tmpfs(void)
 
 	if (chdir(cwd) != 0)
 		err(1, "chdir to private tmpfs");
-
-	if (umount2(".", MNT_DETACH) != 0)
-		err(1, "detach private tmpfs");
 }
 
 static void copy_fromat_to(int fromfd, const char *fromname, const char *toname)
@@ -248,7 +245,7 @@ static int do_tests(int uid, const char *our_path)
 			err(1, "chown");
 		if (chmod("validate_cap_sgidnonroot", S_ISGID | 0710) != 0)
 			err(1, "chmod");
-}
+	}
 
 	capng_get_caps_process();
 
@@ -384,7 +381,7 @@ static int do_tests(int uid, const char *our_path)
 	} else {
 		printf("[RUN]\tNon-root +ia, sgidnonroot => i\n");
 		exec_other_validate_cap("./validate_cap_sgidnonroot",
-						false, false, true, false);
+					false, false, true, false);
 
 		if (fork_wait()) {
 			printf("[RUN]\tNon-root +ia, sgidroot => i\n");
-- 
2.9.4

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