linux-kernel - Re: [PATCH v2] acpi: fix acpi_get_table() leak / acpi-sysfs denial of service

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Date:   Thu, 27 Apr 2017 00:25:01 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Dan Williams <dan.j.williams@...el.com>
Cc:     Rafael Wysocki <rafael.j.wysocki@...el.com>,
        Anush Seetharaman <anush.seetharaman@...el.com>,
        Tiffany Kasanicky <tiffany.j.kasanicky@...el.com>,
        Ryon Jensen <ryon.jensen@...el.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Stable <stable@...r.kernel.org>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        Kristin Jacque <kristin.jacque@...el.com>,
        Zhang Rui <rui.zhang@...el.com>
Subject: Re: [PATCH v2] acpi: fix acpi_get_table() leak / acpi-sysfs denial of service

On Tue, Apr 25, 2017 at 9:58 PM, Dan Williams <dan.j.williams@...el.com> wrote:
> Reading an ACPI table through the /sys/firmware/acpi/tables interface
> more than 65,536 times leads to the following log message:
>
>  ACPI Error: Table ffff88033595eaa8, Validation count is zero after increment
>   (20170119/tbutils-423)
>
> ...and the table being unavailable until the next reboot. Add the
> missing acpi_put_table() so the table ->validation_count is decremented
> after each read.
>
> Cc: <stable@...r.kernel.org>
> Cc: Zhang Rui <rui.zhang@...el.com>
> Cc: Rafael Wysocki <rafael.j.wysocki@...el.com>
> Cc: Kristin Jacque <kristin.jacque@...el.com>
> Cc: Tiffany Kasanicky <tiffany.j.kasanicky@...el.com>
> Cc: Ryon Jensen <ryon.jensen@...el.com>
> Reported-by: Anush Seetharaman <anush.seetharaman@...el.com>
> Fixes: 1c8fce27e275 ("ACPI: introduce drivers/acpi/sysfs.c")
> Signed-off-by: Dan Williams <dan.j.williams@...el.com>

I'm going to apply this, but your Fixes tag is not correct.

validation_count was added to struct acpi_table_desc by commit

commit 174cc7187e6f088942c8e74daa7baff7b44b33c9
Author: Lv Zheng <lv.zheng@...el.com>
Date:   Wed Dec 14 15:04:25 2016 +0800

    ACPICA: Tables: Back port acpi_get_table_with_size() and
early_acpi_os_unmap_memory()
from Linux kernel

from the 4.10 time frame, so IMO it should be

Fixes: 174cc7187e6f (ACPICA: Tables: Back port
acpi_get_table_with_size() and early_acpi_os_unmap_memory() from Linux
kernel)

> ---
>
> Changes in v2:
> * compile fix s/table/table_header/. Sorry, I forgot to do 'stg refresh'
>   before 'stg mail'
>
>  drivers/acpi/sysfs.c |    7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/acpi/sysfs.c b/drivers/acpi/sysfs.c
> index cf05ae973381..5180fef9eb49 100644
> --- a/drivers/acpi/sysfs.c
> +++ b/drivers/acpi/sysfs.c
> @@ -333,14 +333,17 @@ static ssize_t acpi_table_show(struct file *filp, struct kobject *kobj,
>             container_of(bin_attr, struct acpi_table_attr, attr);
>         struct acpi_table_header *table_header = NULL;
>         acpi_status status;
> +       ssize_t rc;
>
>         status = acpi_get_table(table_attr->name, table_attr->instance,
>                                 &table_header);
>         if (ACPI_FAILURE(status))
>                 return -ENODEV;
>
> -       return memory_read_from_buffer(buf, count, &offset,
> -                                      table_header, table_header->length);
> +       rc = memory_read_from_buffer(buf, count, &offset, table_header,
> +                       table_header->length);
> +       acpi_put_table(table_header);
> +       return rc;
>  }
>
>  static int acpi_table_attr_init(struct kobject *tables_obj,
>
> --

Thanks,
Rafael