linux-ext4 - Re: [PATCH v2] fs/{posix_acl,ext2,jfs,ceph}: apply umask if ACL support is disabled

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Date: Thu, 14 Mar 2024 14:08:04 +0100
From: Max Kellermann <max.kellermann@...os.com>
To: Michael Forney <mforney@...rney.org>
Cc: Jan Kara <jack@...e.cz>, "Theodore Ts'o" <tytso@....edu>, Christian Brauner <brauner@...nel.org>, 
	Xiubo Li <xiubli@...hat.com>, Ilya Dryomov <idryomov@...il.com>, Jeff Layton <jlayton@...nel.org>, 
	Jan Kara <jack@...e.com>, Dave Kleikamp <shaggy@...nel.org>, ceph-devel@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-ext4@...r.kernel.org, 
	jfs-discussion@...ts.sourceforge.net, Yang Xu <xuyang2018.jy@...itsu.com>, 
	linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH v2] fs/{posix_acl,ext2,jfs,ceph}: apply umask if ACL
 support is disabled

On Wed, Mar 13, 2024 at 9:39 PM Michael Forney <mforney@...rney.org> wrote:
> Turns out that symlinks are inheriting umask on my system (which
> has CONFIG_EXT4_FS_POSIX_ACL=n):
>
> $ umask 022
> $ ln -s target symlink
> $ ls -l symlink
> lrwxr-xr-x    1 michael  michael           6 Mar 13 13:28 symlink -> target
> $
>
> Looking at the referenced functions, posix_acl_create() returns
> early before applying umask for symlinks, but ext4_init_acl() now
> applies the umask unconditionally.

Indeed, I forgot to exclude symlinks from this - sorry for the breakage.

> After reverting this commit, it works correctly. I am also unable
> to reproduce the mentioned issue with O_TMPFILE after reverting the
> commit. It seems that the bug was fixed properly in ac6800e279a2
> ('fs: Add missing umask strip in vfs_tmpfile'), and all branches
> that have this ext4_init_acl patch already had ac6800e279a2 backported.

I can post a patch that adds the missing check or a revert - what do
the FS maintainers prefer?

(There was a bug with O_TMPFILE ignoring umasks years ago - I first
posted the patch in 2018 or so - but by the time my patch actually got
merged, the bug had already been fixed somewhere else IIRC.)

Max