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efivars: Add module parameter to disable use as a pstore backend

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commit ec0971ba53 upstream.

We know that with some firmware implementations writing too much data to
UEFI variables can lead to bricking machines. Recent changes attempt to
address this issue, but for some it may still be prudent to avoid
writing large amounts of data until the solution has been proven on a
wide variety of hardware.

Crash dumps or other data from pstore can potentially be a large data
source. Add a pstore_module parameter to efivars to allow disabling its
use as a backend for pstore. Also add a config option,
CONFIG_EFI_VARS_PSTORE_DEFAULT_DISABLE, to allow setting the default
value of this paramter to true (i.e. disabled by default).

Signed-off-by: Seth Forshee <seth.forshee@canonical.com>
Cc: Josh Boyer <jwboyer@redhat.com>
Cc: Matthew Garrett <mjg59@srcf.ucam.org>
Cc: Seiji Aguchi <seiji.aguchi@hds.com>
Cc: Tony Luck <tony.luck@intel.com>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Cc: Rui Xiang <rui.xiang@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Seth Forshee 2013-03-11 16:17:50 -05:00 committed by Greg Kroah-Hartman
parent f6a087af82
commit 026f0287cd
2 changed files with 16 additions and 1 deletions
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9
drivers/firmware/Kconfig
View file

@ -62,6 +62,15 @@ config EFI_VARS_PSTORE
will allow writing console messages, crash dumps, or anything
else supported by pstore to EFI variables.
config EFI_VARS_PSTORE_DEFAULT_DISABLE
bool "Disable using efivars as a pstore backend by default"
depends on EFI_VARS_PSTORE
default n
help
Saying Y here will disable the use of efivars as a storage
backend for pstore by default. This setting can be overridden
using the efivars module's pstore_disable parameter.
config EFI_PCDP
bool "Console device selection via EFI PCDP or HCDP table"
depends on ACPI && EFI && IA64

8
drivers/firmware/efivars.c
View file

@ -92,6 +92,11 @@ MODULE_VERSION(EFIVARS_VERSION);
#define DUMP_NAME_LEN 52
static bool efivars_pstore_disable =
IS_ENABLED(EFI_VARS_PSTORE_DEFAULT_DISABLE);
module_param_named(pstore_disable, efivars_pstore_disable, bool, 0644);
/*
* The maximum size of VariableName + Data = 1024
* Therefore, it's reasonable to save that much
@ -1350,7 +1355,8 @@ int register_efivars(struct efivars *efivars,
if (error)
unregister_efivars(efivars);
efivar_pstore_register(efivars);
if (!efivars_pstore_disable)
efivar_pstore_register(efivars);
out:
kfree(variable_name);