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

[Zheng, Lv]

Hi,

> From: linux-acpi-owner@xxxxxxxxxxxxxxx [mailto:linux-acpi-owner@xxxxxxxxxxxxxxx] On Behalf Of Dan
> Williams
> Subject: [PATCH] acpi: fix acpi_get_table() leak / acpi-sysfs denial of service
> 
> 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.

For now, should just return AE_OK instead of AE_LIMIT in acpi_tb_get_table().
Otherwise this fix will not be sufficient to fix all possible problem
Unless we can add acpi_put_table() for all acpi_get_table() invocation.
Let me send a patch for you to try.

Thanks and best regards
Lv

> 
> 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>
> ---
>  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..531ddabf0390 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);
> +	return rc;
>  }
> 
>  static int acpi_table_attr_init(struct kobject *tables_obj,
> 
> --
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