linux-kernel - Re: [PATCH] thermal/int340x_thermal: Prevent page fault on .set

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Message-ID: <CABLO=+kwtYKdEHNsYS13+=LgFZ3L7Snym-aBthxe=vOsjiPTbg@mail.gmail.com>
Date:   Thu, 9 Jul 2020 11:36:18 +0200
From:   Bartosz Szczepanek <bsz@...ihalf.com>
To:     Matthew Garrett <mjg59@...gle.com>,
        Zhang Rui <rui.zhang@...el.com>,
        Pandruvada Srinivas <srinivas.pandruvada@...ux.intel.com>,
        linux-pm@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Cc:     Daniel Lezcano <daniel.lezcano@...aro.org>,
        Amit Kucheria <amit.kucheria@...durent.com>,
        Radoslaw Biernacki <rad@...ihalf.com>,
        Alex Levin <levinale@...gle.com>
Subject: Re: [PATCH] thermal/int340x_thermal: Prevent page fault on
 .set_mode() op

Hi Rui, Matthew,

I think this regression should be corrected still in the 5.8 release
cycle. It may cause kernel panic if .set_mode() is called before
current_uuid_store(), and from what I see both operations can be
triggered from sysfs. What I'm not 100% sure about is if we should
apply the above fix, or rather revert the driver to its default
behaviour of using uuid=0 if it wasn't set from userspace (this is how
it was before Matthew's commit). What do you think?

Best regards,
Bartosz


On Wed, Jul 8, 2020 at 3:46 PM Bartosz Szczepanek <bsz@...ihalf.com> wrote:
>
> Starting from commit "thermal/int340x_thermal: Don't require IDSP to
> exist", priv->current_uuid_index is initialized to -1. This value may
> be passed to int3400_thermal_run_osc() from int3400_thermal_set_mode,
> contributing to page fault when accessing int3400_thermal_uuids array
> at index -1.
>
> This commit adds a check on uuid value to int3400_thermal_run_osc.
>
> Signed-off-by: Bartosz Szczepanek <bsz@...ihalf.com>
> ---
>  drivers/thermal/intel/int340x_thermal/int3400_thermal.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/thermal/intel/int340x_thermal/int3400_thermal.c b/drivers/thermal/intel/int340x_thermal/int3400_thermal.c
> index 0b3a62655843..12448ccd27f1 100644
> --- a/drivers/thermal/intel/int340x_thermal/int3400_thermal.c
> +++ b/drivers/thermal/intel/int340x_thermal/int3400_thermal.c
> @@ -216,11 +216,16 @@ static int int3400_thermal_run_osc(acpi_handle handle,
>         acpi_status status;
>         int result = 0;
>         struct acpi_osc_context context = {
> -               .uuid_str = int3400_thermal_uuids[uuid],
> +               .uuid_str = NULL,
>                 .rev = 1,
>                 .cap.length = 8,
>         };
>
> +       if (uuid < 0 || uuid >= INT3400_THERMAL_MAXIMUM_UUID)
> +               return -EINVAL;
> +
> +       context.uuid_str = int3400_thermal_uuids[uuid];
> +
>         buf[OSC_QUERY_DWORD] = 0;
>         buf[OSC_SUPPORT_DWORD] = enable;
>
> --
> 2.17.1
>