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efi: pstore: Allow dynamic initialization based on module parameter 

The efi-pstore module parameter "pstore_disable" warrants that users
are able to deactivate such backend. There is also a Kconfig option
for the default value of this parameter. It was originally added due
to some bad UEFI FW implementations that could break with many variables
written.

Some distros (such as Arch Linux) set this in their config file still
nowadays. And once it is set, even being a writable module parameter,
there is effectively no way to make use of efi-pstore anymore.
If "pstore_disable" is set to true, the init function of the module exits
early and is never called again after the initcall processing.

Let's switch this module parameter to have a callback and perform the
pstore backend registration again each time it's set from Y->N (and
vice-versa). With this, the writable nature of the parameter starts to
make sense, given that users now can switch back to using efi-pstore
or not during runtime by writing into it.

Signed-off-by: Guilherme G. Piccoli <gpiccoli@igalia.com>
Link: https://lore.kernel.org/r/20240103184053.226203-1-gpiccoli@igalia.com
Signed-off-by: Kees Cook <keescook@chromium.org>
This commit is contained in:
Guilherme G. Piccoli 2024-01-03 15:40:32 -03:00 committed by Kees Cook
parent 77a6557d2a
commit a28655c330
1 changed files with 35 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

43
drivers/firmware/efi/efi-pstore.c
View File

@ -14,16 +14,43 @@ static unsigned int record_size = 1024;
module_param(record_size, uint, 0444);
MODULE_PARM_DESC(record_size, "size of each pstore UEFI var (in bytes, min/default=1024)");
static bool efivars_pstore_disable =
IS_ENABLED(CONFIG_EFI_VARS_PSTORE_DEFAULT_DISABLE);
module_param_named(pstore_disable, efivars_pstore_disable, bool, 0644);
#define PSTORE_EFI_ATTRIBUTES \
(EFI_VARIABLE_NON_VOLATILE | \
EFI_VARIABLE_BOOTSERVICE_ACCESS | \
EFI_VARIABLE_RUNTIME_ACCESS)
static bool pstore_disable = IS_ENABLED(CONFIG_EFI_VARS_PSTORE_DEFAULT_DISABLE);
static int efivars_pstore_init(void);
static void efivars_pstore_exit(void);
static int efi_pstore_disable_set(const char *val, const struct kernel_param *kp)
{
int err;
bool old_pstore_disable = pstore_disable;
err = param_set_bool(val, kp);
if (err)
return err;
if (old_pstore_disable != pstore_disable) {
if (pstore_disable)
efivars_pstore_exit();
else
efivars_pstore_init();
}
return 0;
}
static const struct kernel_param_ops pstore_disable_ops = {
.set = efi_pstore_disable_set,
.get = param_get_bool,
};
module_param_cb(pstore_disable, &pstore_disable_ops, &pstore_disable, 0644);
__MODULE_PARM_TYPE(pstore_disable, "bool");
static int efi_pstore_open(struct pstore_info *psi)
{
int err;
@ -218,12 +245,12 @@ static struct pstore_info efi_pstore_info = {
.erase = efi_pstore_erase,
};
static __init int efivars_pstore_init(void)
static int efivars_pstore_init(void)
{
if (!efivar_supports_writes())
return 0;
if (efivars_pstore_disable)
if (pstore_disable)
return 0;
/*
@ -250,7 +277,7 @@ static __init int efivars_pstore_init(void)
return 0;
}
static __exit void efivars_pstore_exit(void)
static void efivars_pstore_exit(void)
{
if (!efi_pstore_info.bufsize)
return;