diff mbox series

[v3,1/4] fs/posix_acl: apply umask if superblock disables ACL support

Message ID 20200407142243.2032-1-mk@cm4all.com (mailing list archive)
State New, archived
Headers show
Series [v3,1/4] fs/posix_acl: apply umask if superblock disables ACL support | expand

Commit Message

Max Kellermann April 7, 2020, 2:22 p.m. UTC 
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
succeeded.  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 <mk@cm4all.com>
Reviewed-by: J. Bruce Fields <bfields@redhat.com>
Cc: stable@vger.kernel.org
---
 fs/posix_acl.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

Comments

Christoph Hellwig April 17, 2020, 7:35 a.m. UTC | #1 
On Tue, Apr 07, 2020 at 04:22:40PM +0200, Max Kellermann wrote:
>  
> -	if (S_ISLNK(*mode) || !IS_POSIXACL(dir))
> +	if (S_ISLNK(*mode))
>  		return 0;
>  
> +	if (!IS_POSIXACL(dir)) {
> +		*mode &= ~current_umask();
> +		return 0;
> +	}
> +

I think the first hunk is obviously correct, but I don't think we need
the second one, as the handling of the get_acl() eturn value should do
the right thing.  If you want to optimize it a bit, it might be worth to
move the !IS_POSIXACL check in get_acl to the top of the function,
before checking the cached ACL.
diff mbox series

Patch

diff --git a/fs/posix_acl.c b/fs/posix_acl.c
index 249672bf54fe..e5e7a2295b99 100644
--- a/fs/posix_acl.c
+++ b/fs/posix_acl.c
@@ -589,9 +589,14 @@  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();