Message-ID: <440B4799.7030609@ens-lyon.org>
Date: Sun, 05 Mar 2006 15:18:33 -0500
From: Brice Goglin <Brice.Goglin@ens-lyon.org>
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To: Aritz Bastida <aritzbastida@gmail.com>
CC: linux-kernel@vger.kernel.org
Subject: Re: MMAP: How a driver can get called on mprotect()
References: <7d40d7190603051012p16ed826cx@mail.gmail.com>	 <20060305182240.GH19232@lug-owl.de> <7d40d7190603051040h17da06caw@mail.gmail.com>
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Aritz Bastida wrote:

>Nonetheless the question is the same: a char device with mmap
>implemented can get called any time a new vma is created or destroyed
>(a process creating a new mmap):  vma_open() and vma_close().
>
>But if a user process changes the mmap protections calling mprotect()?
>How can the driver know about that? Is there any way to do that?
>  
>

You probably want to remove VM_MAYWRITE from vma->vm_flags in the mmap
vm_op of your char device.
For instance, see how the DRM device mmap protection is set when you're
not admin and the device is read-only:
    http://sosdg.org/~coywolf/lxr/source/drivers/char/drm/drm_vm.c#L570

Brice

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