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efi: Make efivarfs entries immutable by default

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"rm -rf" is bricking some peoples' laptops because of variables being
used to store non-reinitializable firmware driver data that's required
to POST the hardware.

These are 100% bugs, and they need to be fixed, but in the mean time it
shouldn't be easy to *accidentally* brick machines.

We have to have delete working, and picking which variables do and don't
work for deletion is quite intractable, so instead make everything
immutable by default (except for a whitelist), and make tools that
aren't quite so broad-spectrum unset the immutable flag.

Signed-off-by: Peter Jones <pjones@redhat.com>
Tested-by: Lee, Chun-Yi <jlee@suse.com>
Acked-by: Matthew Garrett <mjg59@coreos.com>
Signed-off-by: Matt Fleming <matt@codeblueprint.co.uk>
This commit is contained in:
Peter Jones
2016-02-08 14:48:15 -05:00
committed by Matt Fleming
parent 8282f5d9c1
commit ed8b0de5a3
9 changed files with 258 additions and 41 deletions
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87
drivers/firmware/efi/vars.c
View File

@@ -172,10 +172,12 @@ struct variable_validate {
};
/*
* This is the list of variables we need to validate.
* This is the list of variables we need to validate, as well as the
* whitelist for what we think is safe not to default to immutable.
*
* If it has a validate() method that's not NULL, it'll go into the
* validation routine. If not, it is assumed valid.
* validation routine. If not, it is assumed valid, but still used for
* whitelisting.
*
* Note that it's sorted by {vendor,name}, but globbed names must come after
* any other name with the same prefix.
@@ -193,11 +195,37 @@ static const struct variable_validate variable_validate[] = {
{ EFI_GLOBAL_VARIABLE_GUID, "ErrOut", validate_device_path },
{ EFI_GLOBAL_VARIABLE_GUID, "ErrOutDev", validate_device_path },
{ EFI_GLOBAL_VARIABLE_GUID, "Lang", validate_ascii_string },
{ EFI_GLOBAL_VARIABLE_GUID, "OsIndications", NULL },
{ EFI_GLOBAL_VARIABLE_GUID, "PlatformLang", validate_ascii_string },
{ EFI_GLOBAL_VARIABLE_GUID, "Timeout", validate_uint16 },
{ NULL_GUID, "", NULL },
};
static bool
variable_matches(const char *var_name, size_t len, const char *match_name,
int *match)
{
for (*match = 0; ; (*match)++) {
char c = match_name[*match];
char u = var_name[*match];
/* Wildcard in the matching name means we've matched */
if (c == '*')
return true;
/* Case sensitive match */
if (!c && *match == len)
return true;
if (c != u)
return false;
if (!c)
return true;
}
return true;
}
bool
efivar_validate(efi_guid_t vendor, efi_char16_t *var_name, u8 *data,
unsigned long data_size)
@@ -221,35 +249,48 @@ efivar_validate(efi_guid_t vendor, efi_char16_t *var_name, u8 *data,
if (efi_guidcmp(vendor, variable_validate[i].vendor))
continue;
for (match = 0; ; match++) {
char c = name[match];
char u = utf8_name[match];
/* Wildcard in the matching name means we've matched */
if (c == '*') {
kfree(utf8_name);
return variable_validate[i].validate(var_name,
match, data, data_size);
}
/* Case sensitive match */
if (c != u)
if (variable_matches(utf8_name, utf8_size+1, name, &match)) {
if (variable_validate[i].validate == NULL)
break;
/* Reached the end of the string while matching */
if (!c) {
kfree(utf8_name);
return variable_validate[i].validate(var_name,
match, data, data_size);
}
kfree(utf8_name);
return variable_validate[i].validate(var_name, match,
data, data_size);
}
}
kfree(utf8_name);
return true;
}
EXPORT_SYMBOL_GPL(efivar_validate);
bool
efivar_variable_is_removable(efi_guid_t vendor, const char *var_name,
size_t len)
{
int i;
bool found = false;
int match = 0;
/*
* Check if our variable is in the validated variables list
*/
for (i = 0; variable_validate[i].name[0] != '\0'; i++) {
if (efi_guidcmp(variable_validate[i].vendor, vendor))
continue;
if (variable_matches(var_name, len,
variable_validate[i].name, &match)) {
found = true;
break;
}
}
/*
* If it's in our list, it is removable.
*/
return found;
}
EXPORT_SYMBOL_GPL(efivar_variable_is_removable);
static efi_status_t
check_var_size(u32 attributes, unsigned long size)
{