linux-kernel - Re: [PATCH v2 1/5] efi_pstore: Check remaining space with QueryVariableInfo() before writing data

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Date:	Thu, 25 Oct 2012 11:56:13 -0700
From:	Mike Waychison <mikew@...gle.com>
To:	Seiji Aguchi <seiji.aguchi@....com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-efi@...r.kernel.org" <linux-efi@...r.kernel.org>,
	"linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
	"Luck, Tony (tony.luck@...el.com)" <tony.luck@...el.com>,
	"Matthew Garrett (mjg@...hat.com)" <mjg@...hat.com>,
	"dzickus@...hat.com" <dzickus@...hat.com>,
	"dle-develop@...ts.sourceforge.net" 
	<dle-develop@...ts.sourceforge.net>,
	Satoru Moriya <satoru.moriya@....com>
Subject: Re: [PATCH v2 1/5] efi_pstore: Check remaining space with
 QueryVariableInfo() before writing data

Acked-by: Mike Waychison <mikew@...gle.com>

On Wed, Oct 24, 2012 at 6:51 PM, Seiji Aguchi <seiji.aguchi@....com> wrote:
> [Issue]
>
> As discussed in a thread below, Running out of space in EFI isn't a well-tested scenario.
> And we wouldn't expect all firmware to handle it gracefully.
> http://marc.info/?l=linux-kernel&m=134305325801789&w=2
>
> On the other hand, current efi_pstore doesn't check a remaining space of storage at writing time.
> Therefore, efi_pstore may not work if it tries to write a large amount of data.
>
> [Patch Description]
>
> To avoid handling the situation above, this patch checks if there is a space enough to log with
> QueryVariableInfo() before writing data.
>
> Signed-off-by: Seiji Aguchi <seiji.aguchi@....com>
> ---
>  drivers/firmware/efivars.c |   18 ++++++++++++++++++
>  include/linux/efi.h        |    1 +
>  2 files changed, 19 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/firmware/efivars.c b/drivers/firmware/efivars.c
> index d10c987..37ac21a 100644
> --- a/drivers/firmware/efivars.c
> +++ b/drivers/firmware/efivars.c
> @@ -707,12 +707,29 @@ static int efi_pstore_write(enum pstore_type_id type,
>         struct efivars *efivars = psi->data;
>         struct efivar_entry *entry, *found = NULL;
>         int i, ret = 0;
> +       u64 storage_space, remaining_space, max_variable_size;
> +       efi_status_t status = EFI_NOT_FOUND;
>
>         sprintf(stub_name, "dump-type%u-%u-", type, part);
>         sprintf(name, "%s%lu", stub_name, get_seconds());
>
>         spin_lock(&efivars->lock);
>
> +       /*
> +        * Check if there is a space enough to log.
> +        * size: a size of logging data
> +        * DUMP_NAME_LEN * 2: a maximum size of variable name
> +        */
> +       status = efivars->ops->query_variable_info(PSTORE_EFI_ATTRIBUTES,
> +                                                  &storage_space,
> +                                                  &remaining_space,
> +                                                  &max_variable_size);
> +       if (status || remaining_space < size + DUMP_NAME_LEN * 2) {
> +               spin_unlock(&efivars->lock);
> +               *id = part;
> +               return -ENOSPC;
> +       }
> +
>         for (i = 0; i < DUMP_NAME_LEN; i++)
>                 efi_name[i] = stub_name[i];
>
> @@ -1237,6 +1254,7 @@ efivars_init(void)
>         ops.get_variable = efi.get_variable;
>         ops.set_variable = efi.set_variable;
>         ops.get_next_variable = efi.get_next_variable;
> +       ops.query_variable_info = efi.query_variable_info;
>         error = register_efivars(&__efivars, &ops, efi_kobj);
>         if (error)
>                 goto err_put;
> diff --git a/include/linux/efi.h b/include/linux/efi.h
> index 8670eb1..c47ec36 100644
> --- a/include/linux/efi.h
> +++ b/include/linux/efi.h
> @@ -643,6 +643,7 @@ struct efivar_operations {
>         efi_get_variable_t *get_variable;
>         efi_get_next_variable_t *get_next_variable;
>         efi_set_variable_t *set_variable;
> +       efi_query_variable_info_t *query_variable_info;
>  };
>
>  struct efivars {
> -- 1.7.1
--
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