On Mon, Apr 3, 2017 at 12:00 PM, Ross Zwisler
<ross.zwisler@xxxxxxxxxxxxxxx> wrote:
> On Sat, Apr 01, 2017 at 12:25:20PM -0700, Dan Williams wrote:
>> Calls to acpi_get_table() must be paired with acpi_put_table() to undo
>> the mapping established by acpi_tb_acquire_table().
>>
>> Cc: <stable@xxxxxxxxxxxxxxx>
>> Fixes: 6b11d1d67713 ("ACPI / osl: Remove acpi_get_table_with_size()/early_acpi_os_unmap_memory() users")
>> Cc: Lv Zheng <lv.zheng@xxxxxxxxx>
>> Reported-by: Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx>
>> Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
>> ---
>> drivers/acpi/nfit/core.c | 9 +++++++++
>> 1 file changed, 9 insertions(+)
>>
>> diff --git a/drivers/acpi/nfit/core.c b/drivers/acpi/nfit/core.c
>> index c8ea9d698cd0..6acfea69f061 100644
>> --- a/drivers/acpi/nfit/core.c
>> +++ b/drivers/acpi/nfit/core.c
>> @@ -2818,6 +2818,11 @@ void acpi_nfit_desc_init(struct acpi_nfit_desc *acpi_desc, struct device *dev)
>> }
>> EXPORT_SYMBOL_GPL(acpi_nfit_desc_init);
>>
>> +static void acpi_nfit_put_table(void *table)
>> +{
>> + acpi_put_table(table);
>> +}
>> +
>> static int acpi_nfit_add(struct acpi_device *adev)
>> {
>> struct acpi_buffer buf = { ACPI_ALLOCATE_BUFFER, NULL };
>> @@ -2834,6 +2839,10 @@ static int acpi_nfit_add(struct acpi_device *adev)
>> dev_dbg(dev, "failed to find NFIT at startup\n");
>> return 0;
>> }
>> +
>> + rc = devm_add_action_or_reset(dev, acpi_nfit_put_table, tbl);
>> + if (rc)
>> + return rc;
>> sz = tbl->length;
>>
>> acpi_desc = devm_kzalloc(dev, sizeof(*acpi_desc), GFP_KERNEL);
>
> I've been looking at this this as well, and I think it might be better to just
> drop the reference immediately in acpi_nfit_add() after we're done processing
> the tables?
>
> Anyway, here's the patch I was working on, but I think either works.
>
> ------ 8< ------
> From 4819cd889b08c3c17f8f9fcf895a083f21fa0898 Mon Sep 17 00:00:00 2001
> From: Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx>
> Date: Mon, 3 Apr 2017 11:53:32 -0600
> Subject: [PATCH] nfit: release reference on ACPI nfit table
>
> Currently acpi_nfit_add() grabs a reference to the ACPI NFIT table
> structures via acpi_get_table(), but never releases it with
> acpi_put_table(). This means that the refcount protecting the ioremap for
> the NFIT table never decrements, so the ioremap can never be undone. The
> ioremap happens via this path:
>
> acpi_get_table()
> acpi_tb_get_table()
> acpi_tb_validate_table()
> acpi_tb_acquire_table()
> acpi_os_map_memory()
>
> In practice this fix is correct but won't have a usable visible impact
> because the ACPI sysfs code (acpi_table_attr_init() et al.), which
> populates /sys/firmware/acpi/tables/NFIT, also keeps a table reference, so
> the NFIT table memory will always remain mapped.
>
> We drop the refcount at the end of acpi_nfit_add() instead of waiting till
> driver unload and doing it via acpi_nfit_remove() or something akin to
> acpi_nfit_destruct() called via the devm_ interface. This is because
> during acpi_nfit_add() we never actually keep any references to the
> original ACPI tables. We either copy individual elements out, or we make
> whole copies of tables in functions like add_spa(), add memdev(), etc.
>
> Signed-off-by: Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx>
> ---
> drivers/acpi/nfit/core.c | 8 ++++++--
> 1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/acpi/nfit/core.c b/drivers/acpi/nfit/core.c
> index 662036b..ad0dfd6 100644
> --- a/drivers/acpi/nfit/core.c
> +++ b/drivers/acpi/nfit/core.c
> @@ -2833,8 +2833,10 @@ static int acpi_nfit_add(struct acpi_device *adev)
> sz = tbl->length;
>
> acpi_desc = devm_kzalloc(dev, sizeof(*acpi_desc), GFP_KERNEL);
> - if (!acpi_desc)
> - return -ENOMEM;
> + if (!acpi_desc) {
> + rc = -ENOMEM;
> + goto out;
> + }
> acpi_nfit_desc_init(acpi_desc, &adev->dev);
>
> /* Save the acpi header for exporting the revision via sysfs */
> @@ -2857,6 +2859,8 @@ static int acpi_nfit_add(struct acpi_device *adev)
> rc = acpi_nfit_init(acpi_desc, (void *) tbl
> + sizeof(struct acpi_table_nfit),
> sz - sizeof(struct acpi_table_nfit));
> +out:
> + acpi_put_table(tbl);
> return rc;
> }
Hi Ross, thanks for this. I'll add your note about this fix not making
a difference in practice to my devm_add_action_or_reset() version and
drop -stable. I don't want to maintain gotos in the init path if at
all possible.