From ed8b0de5a33d2a2557dce7f9429dca8cb5bc5879 Mon Sep 17 00:00:00 2001 From: Peter Jones Date: Mon, 8 Feb 2016 14:48:15 -0500 Subject: 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 Tested-by: Lee, Chun-Yi Acked-by: Matthew Garrett Signed-off-by: Matt Fleming --- drivers/firmware/efi/vars.c | 87 +++++++++++++++++++++++++++++++++------------ 1 file changed, 64 insertions(+), 23 deletions(-) (limited to 'drivers/firmware/efi/vars.c') diff --git a/drivers/firmware/efi/vars.c b/drivers/firmware/efi/vars.c index 9a53da21e7b6..50f10bad2604 100644 --- a/drivers/firmware/efi/vars.c +++ b/drivers/firmware/efi/vars.c @@ -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) { -- cgit v1.2.3