linux-kernel - Re: [PATCH] fs/posix_acl: apply umask if superblock disables ACL support

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Date:   Tue, 19 Sep 2023 15:10:10 +0200
From:   Christian Brauner <brauner@...nel.org>
To:     Max Kellermann <max.kellermann@...os.com>
Cc:     Alexander Viro <viro@...iv.linux.org.uk>,
        "J . Bruce Fields" <bfields@...hat.com>, stable@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] fs/posix_acl: apply umask if superblock disables ACL
 support

On Tue, Sep 19, 2023 at 10:18:07AM +0200, Max Kellermann wrote:
> 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.

The fix is in the wrong place if !IS_POSIXACL() umask stripping happens
in the VFS. So if at all we need to fix stripping umask for O_TMPFILE in
the vfs.

Have you verified that commit ac6800e279a2 ("fs: Add missing umask strip
in vfs_tmpfile") doesn't already fix this?