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From:   David Howells <dhowells@redhat.com>
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To:     Andy Lutomirski <luto@amacapital.net>
Cc:     dhowells@redhat.com, Andy Lutomirski <luto@kernel.org>,
        Casey Schaufler <casey@schaufler-ca.com>,
        Stephen Smalley <sds@tycho.nsa.gov>,
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        USB list <linux-usb@vger.kernel.org>, raven@themaw.net,
        Linux FS Devel <linux-fsdevel@vger.kernel.org>,
        Linux API <linux-api@vger.kernel.org>,
        linux-block@vger.kernel.org, keyrings@vger.kernel.org,
        LSM List <linux-security-module@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Paul Moore <paul@paul-moore.com>
Subject: Re: [RFC][PATCH 00/10] Mount, FS, Block and Keyrings notifications [ver #3]
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Date:   Thu, 06 Jun 2019 23:38:01 +0100
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Andy Lutomirski <luto@amacapital.net> wrote:

> I mean: are there cases where some action generates a notification but does
> not otherwise have an effect visible to the users who can receive the
> notification. It looks like the answer is probably “no”, which is good.

mount_notify().  You can get a notification that someone altered the mount
topology (eg. by mounting something).  A process receiving a notification
could then use fsinfo(), say, to reread the mount topology tree, find out
where the new mount is and wander over there to have a look - assuming they
have the permissions for pathwalk to succeed.

David