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

From: Rafael J. Wysocki
Date: Wed Apr 26 2017 - 18:25:34 EST


On Tue, Apr 25, 2017 at 9:58 PM, Dan Williams <dan.j.williams@xxxxxxxxx> 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@xxxxxxxxxxxxxxx>
> Cc: Zhang Rui <rui.zhang@xxxxxxxxx>
> Cc: Rafael Wysocki <rafael.j.wysocki@xxxxxxxxx>
> Cc: Kristin Jacque <kristin.jacque@xxxxxxxxx>
> Cc: Tiffany Kasanicky <tiffany.j.kasanicky@xxxxxxxxx>
> Cc: Ryon Jensen <ryon.jensen@xxxxxxxxx>
> Reported-by: Anush Seetharaman <anush.seetharaman@xxxxxxxxx>
> Fixes: 1c8fce27e275 ("ACPI: introduce drivers/acpi/sysfs.c")
> Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>

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@xxxxxxxxx>
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