efi: Make efivarfs entries immutable by default
"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>
diff --git a/drivers/firmware/efi/vars.c b/drivers/firmware/efi/vars.c
index 9a53da2..50f10ba 100644
--- a/drivers/firmware/efi/vars.c
+++ b/drivers/firmware/efi/vars.c
@@ -172,10 +172,12 @@
};
/*
- * 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 @@
{ 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 @@
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)
{