linux-kernel - Re: fanotify and namespaces/bind mounts

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Message-ID: <CALRD3qKVCeHcskKYP0Ak_Nb4vuEbvH9n8FWZStVp-ZksyK+7OQ@mail.gmail.com>
Date:   Sat, 18 Mar 2017 10:04:00 -0400
From:   riya khanna <riyakhanna1983@...il.com>
To:     Marko Rauhamaa <marko@...ujo.net>
Cc:     linux-kernel@...r.kernel.org
Subject: Re: fanotify and namespaces/bind mounts

Are fsnotify events generated per mount namespace?

On Thu, Oct 29, 2015 at 9:29 AM, Marko Rauhamaa <marko@...ujo.net> wrote:
>
> If I call fanotify_mark(... FAN_MARK_ADD | FAN_MARK_MOUNT ...), I get
> notifications on all files on the file system.
>
> Except I don't.
>
> If a process has mounted directories on the file system in a different
> namespace, the global namespace experiences file system events but no
> fanotify events are generated. A similar limitation applies to bind
> mounts.
>
> You can easily see this behavior in action. Do "man fanotify", and copy
> the example program to, say, example.c. Then,
>
>     cc -o example example.c
>     mkdir -p /mnt/xyz
>     mount -o bind /root /mnt/xyz
>     ./example /root
>
> The last command prints out fanotify events. It will display events for
>
>     touch /root/xyzzy
>
> but nothing for
>
>     touch /mnt/xyz/zyxxy
>
> or
>
>     unshare -m touch /root/yxyyx
>
> Should the current situation be considered a bug in fanotify? Or is
> there another recommended way to monitor file system events
> categorigally?
>
>
> Marko
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