linux-kernel - Re: [PATCH v2 1/4] fs/posix_acl: apply umask if superblock disables ACL support

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Date:   Tue, 20 Aug 2019 17:26:52 -0400
From:   bfields@...ldses.org (J. Bruce Fields)
To:     Max Kellermann <mk@...all.com>
Cc:     linux-fsdevel@...r.kernel.org, linux-nfs@...r.kernel.org,
        trond.myklebust@...merspace.com, bfields@...hat.com, tytso@....edu,
        adilger.kernel@...ger.ca, hughd@...gle.com,
        anna.schumaker@...app.com, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org
Subject: Re: [PATCH v2 1/4] fs/posix_acl: apply umask if superblock disables
 ACL support

What happened to these patches?  All four make sense to me, for what
it's worth; feel free to add a

	Reviewed-by: J. Bruce Fields <bfields@...hat.com>

--b.

On Sat, Jul 13, 2019 at 06:11:57AM +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
> 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 <mk@...all.com>
> Cc: stable@...r.kernel.org
> ---
>  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 84ad1c90d535..4071c66f234a 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();
> -- 
> 2.20.1