linux-kernel - Re: [PATCH v3 5/5] soc: qcom: cmd-db: Map with read-only mappings

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAE=gft6=4m79QX8Bca9izRUUkumio_YKBNY8aY=XPjj=WE_BYA@mail.gmail.com>
Date:   Wed, 18 Sep 2019 12:40:52 -0700
From:   Evan Green <evgreen@...omium.org>
To:     Stephen Boyd <swboyd@...omium.org>
Cc:     Dan Williams <dan.j.williams@...el.com>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        linux-arm Mailing List <linux-arm-kernel@...ts.infradead.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>, Rob Herring <robh+dt@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Andy Gross <agross@...nel.org>,
        Will Deacon <will.deacon@....com>,
        Catalin Marinas <catalin.marinas@....com>
Subject: Re: [PATCH v3 5/5] soc: qcom: cmd-db: Map with read-only mappings

On Tue, Sep 10, 2019 at 9:09 AM Stephen Boyd <swboyd@...omium.org> wrote:
>
> The command DB is read-only already to the kernel because everything is
> const marked once we map it. Let's go one step further and try to map
> the memory as read-only in the page tables. This should make it harder
> for random code to corrupt the database and change the contents.
>
> Cc: Evan Green <evgreen@...omium.org>
> Cc: Rob Herring <robh+dt@...nel.org>
> Cc: Bjorn Andersson <bjorn.andersson@...aro.org>
> Cc: Andy Gross <agross@...nel.org>
> Cc: Will Deacon <will.deacon@....com>
> Cc: Catalin Marinas <catalin.marinas@....com>
> Cc: Dan Williams <dan.j.williams@...el.com>
> Reviewed-by: Bjorn Andersson <bjorn.andersson@...aro.org>
> Signed-off-by: Stephen Boyd <swboyd@...omium.org>
> ---
>  drivers/soc/qcom/cmd-db.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/soc/qcom/cmd-db.c b/drivers/soc/qcom/cmd-db.c
> index 10a34d26b753..6365e8260282 100644
> --- a/drivers/soc/qcom/cmd-db.c
> +++ b/drivers/soc/qcom/cmd-db.c
> @@ -240,7 +240,8 @@ static int cmd_db_dev_probe(struct platform_device *pdev)
>  {
>         int ret = 0;
>
> -       cmd_db_header = devm_memremap_reserved_mem(&pdev->dev, MEMREMAP_WB);
> +       cmd_db_header = devm_memremap_reserved_mem(&pdev->dev,
> +                                                  MEMREMAP_RO | MEMREMAP_WB);

It seems weird to have both flags, like: "It's read-only, but if it
ever did get written to somehow, make it writeback".

>         if (IS_ERR(cmd_db_header)) {
>                 ret = PTR_ERR(cmd_db_header);
>                 cmd_db_header = NULL;
> --
> Sent by a computer through tubes
>