linux-kernel - Re: [PATCH] ACPI: EC: Ignore ECDT tables with an invalid ID string

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Message-ID: <CAJZ5v0iWS=tHAuauHNHb+N9_GjJTX2-RY01eAS8-sjS_2UZaoA@mail.gmail.com>
Date: Tue, 10 Jun 2025 20:56:38 +0200
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: Armin Wolf <W_Armin@....de>
Cc: rafael@...nel.org, lenb@...nel.org, glpnk@...ton.me, 
	linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ACPI: EC: Ignore ECDT tables with an invalid ID string

On Fri, May 30, 2025 at 1:53 AM Armin Wolf <W_Armin@....de> wrote:
>
> On the MSI Modern 14 C5M the ECDT table contains invalid data:
>
>         UID : 00000000
>  GPE Number : 00        /* Invalid, 03 would be correct */
>    Namepath : ""        /* Invalid, "\_SB.PCI0.SBRG.EC" would
>                          * be correct
>                          */
>
> This slows down the EC access as the wrong GPE event is used for
> communication. Additionally the ID string is invalid.
>
> Ignore such faulty ECDT tables by verifying that the ID string has
> a valid format.
>
> Tested-by: glpnk@...ton.me
> Signed-off-by: Armin Wolf <W_Armin@....de>
> ---
>  drivers/acpi/ec.c | 17 +++++++++++++++++
>  1 file changed, 17 insertions(+)
>
> diff --git a/drivers/acpi/ec.c b/drivers/acpi/ec.c
> index 6f4203716b53..75c7db8b156a 100644
> --- a/drivers/acpi/ec.c
> +++ b/drivers/acpi/ec.c
> @@ -23,8 +23,10 @@
>  #include <linux/delay.h>
>  #include <linux/interrupt.h>
>  #include <linux/list.h>
> +#include <linux/printk.h>
>  #include <linux/spinlock.h>
>  #include <linux/slab.h>
> +#include <linux/string.h>
>  #include <linux/suspend.h>
>  #include <linux/acpi.h>
>  #include <linux/dmi.h>
> @@ -2031,6 +2033,21 @@ void __init acpi_ec_ecdt_probe(void)
>                 goto out;
>         }
>
> +       if (!strstarts(ecdt_ptr->id, "\\")) {
> +               /*
> +                * The ECDT table on some MSI notebooks contains invalid data, together
> +                * with an empty ID string ("").
> +                *
> +                * Section 5.2.15 of the ACPI specification requires the ID string to be
> +                * a "fully qualified reference to the (...) embedded controller device",
> +                * so this string always has to start with a backslash.
> +                *
> +                * By verifying this we can avoid such faulty ECDT tables in a safe way.
> +                */
> +               pr_err(FW_BUG "Ignoring ECDT due to invalid ID string \"%s\"\n", ecdt_ptr->id);
> +               goto out;
> +       }
> +
>         ec = acpi_ec_alloc();
>         if (!ec)
>                 goto out;
> --

Applied as 6.16-rc material, thanks!