Received-SPF: pass (google.com: best guess record for domain of linux-nfs-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
From:   Max Kellermann <max.kellermann@gmail.com>
To:     linux-fsdevel@vger.kernel.org, linux-nfs@vger.kernel.org,
        trond.myklebust@hammerspace.com, bfields@redhat.com,
        gregkh@linuxfoundation.org, tytso@mit.edu,
        adilger.kernel@dilger.ca, hughd@google.com,
        anna.schumaker@netapp.com
Cc:     linux-kernel@vger.kernel.org,
        Max Kellermann <max.kellermann@gmail.com>
Subject: [PATCH 1/4] fs/posix_acl: apply umask if superblock disables ACL support
Date:   Wed,  3 Jul 2019 14:47:12 +0200
Message-Id: <20190703124715.4319-1-max.kellermann@gmail.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Sender: linux-nfs-owner@vger.kernel.org
Precedence: bulk

The function posix_acl_create() applies the umask only if the inode
has no ACL (= NULL) or if ACLs are not supported by the filesystem
driver (= -EOPNOTSUPP).

However, this happens only after after the IS_POSIXACL() check
succeeeded.  If the superblock doesn't enable ACL support, umask will
never be applied.  A filesystem which has no ACL support will of
course not enable SB_POSIXACL, rendering the umask-applying code path
unreachable.

This fixes a bug which causes the umask to be ignored with O_TMPFILE
on tmpfs:

 https://github.com/MusicPlayerDaemon/MPD/issues/558
 https://bugs.gentoo.org/show_bug.cgi?id=686142#c3
 https://bugzilla.kernel.org/show_bug.cgi?id=203625

Signed-off-by: Max Kellermann <max.kellermann@gmail.com>
---
 fs/posix_acl.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/fs/posix_acl.c b/fs/posix_acl.c
index 2fd0fde16fe1..815f7b36ef94 100644
--- a/fs/posix_acl.c
+++ b/fs/posix_acl.c
@@ -588,9 +588,14 @@ posix_acl_create(struct inode *dir, umode_t *mode,
 	*acl = NULL;
 	*default_acl = NULL;
 
-	if (S_ISLNK(*mode) || !IS_POSIXACL(dir))
+	if (S_ISLNK(*mode))
 		return 0;
 
+	if (!IS_POSIXACL(dir)) {
+		*mode &= ~current_umask();
+		return 0;
+	}
+
 	p = get_acl(dir, ACL_TYPE_DEFAULT);
 	if (!p || p == ERR_PTR(-EOPNOTSUPP)) {
 		*mode &= ~current_umask();
-- 
2.20.1