linux-kernel - Re: Ensure FMODE_NONOTIFY is not set by userspace

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Date:	Fri, 29 Oct 2010 16:27:52 +0200
From:	Lino Sanfilippo <LinoSanfilippo@....de>
To:	Eric Paris <eparis@...hat.com>
Cc:	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: Ensure FMODE_NONOTIFY is not set by userspace

On Fri, Oct 29, 2010 at 09:52:50AM -0400, Eric Paris wrote:
> 
> Did you find a place where the user was able to set FMODE_NONOTIFY?
> That would be a problem.  But that's not what is happening here and
> that's not what you are fixing.

I know its not happening here, but doing something like

#define MY_FLAG 0x1000000

 open("file/within/fanotify_protection", O_RDONLY | MY_FLAG);

from userspace is all that is needed to be ignored by fanotify :)
There is nothing that checks if this flag has been set by userspace (or 
did I miss something?)

Beside this since the flag should only be set within create_fd() or
fanotify_init() there should never be a situation where 
fsnotify_open() is called with a FMODE_NONOTIFY set (by the kernel).

Regards,
Lino 
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