linux-kernel - Re: file system permissions regression affecting root

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Message-ID: <CACh33FqzSc26qyvdueZ3ee28j28cyz42n++xnE=BUXe507NLKA@mail.gmail.com>
Date:   Wed, 13 May 2020 09:52:17 -0700
From:   Patrick Donnelly <batrick@...bytes.com>
To:     Al Viro <viro@...iv.linux.org.uk>
Cc:     open list <linux-kernel@...r.kernel.org>,
        Jeff Layton <jlayton@...hat.com>, xiubli@...hat.com,
        kchai@...hat.com
Subject: Re: file system permissions regression affecting root

On Wed, May 13, 2020 at 9:11 AM Al Viro <viro@...iv.linux.org.uk> wrote:
>
> On Wed, May 13, 2020 at 08:00:28AM -0700, Patrick Donnelly wrote:
> > In newer kernels (at least 5.6), it appears root is not able to write
> > to files owned by other users in a sticky directory:
>
> Yes.  Controlled by /proc/sys/fs/protected_regular, which systemd crowd
> has decided to enable in commit 2732587540035227fe59e4b64b60127352611b35
>  [...]

Thanks for the information Al!

However, it seems odd that this depends on the owner of the directory.
i.e. this protection only seems to be enforced if the sticky directory
is owned by root. That's expected?


-- 
Patrick Donnelly