linux-kernel - Re: [PATCH] usb: mon: make mmapped memory read only

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Message-ID: <CACT4Y+Y5YxAQf=1BJzMYkQyhHaKMCah0Ucq7-Ekfj4xk5bD-sw@mail.gmail.com>
Date:   Mon, 19 Sep 2022 13:21:11 +0200
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     tadeusz.struk@...aro.org
Cc:     gregkh@...uxfoundation.org, linux-kernel@...r.kernel.org,
        linux-usb@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH] usb: mon: make mmapped memory read only

On Mon, 19 Sept 2022 at 06:25, Dmitry Vyukov <dvyukov@...gle.com> wrote:
>
> Hi Tadeusz,
>
> Looking at places like these:
> https://elixir.bootlin.com/linux/v6.0-rc5/source/drivers/infiniband/hw/qib/qib_file_ops.c#L736
> https://elixir.bootlin.com/linux/v6.0-rc5/source/drivers/infiniband/hw/mlx5/main.c#L2088
> I think we also need to remove VM_MAYWRITE, otherwise it's still
> possible to turn it into a writable mapping with mprotect.
>
> It's also probably better to return an error if VM_WRITE (or VM_EXEC?) is set
> rather than silently fix it up.


The credit for the VM_MAYWRITE suggestion goes to the PaX Team.

Suggested-by: PaX Team <pageexec@...email.hu>