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46908326c6
Branden reports that commitf88814cc25("efi/efivars: Expose RT service availability via efivars abstraction") regresses UEFI platforms that implement GetVariable but not SetVariable when booting kernels that have EFIBC (bootloader control) enabled. The reason is that EFIBC is a user of the efivars abstraction, which was updated to permit users that rely only on the read capability, but not on the write capability. EFIBC is in the latter category, so it has to check explicitly whether efivars supports writes. Fixes:f88814cc25("efi/efivars: Expose RT service availability via efivars abstraction") Tested-by: Branden Sherrell <sherrellbc@gmail.com> Link: https://lore.kernel.org/linux-efi/AE217103-C96F-4AFC-8417-83EC11962004@gmail.com/ Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
108 lines
2.5 KiB
C
108 lines
2.5 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* efibc: control EFI bootloaders which obey LoaderEntryOneShot var
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* Copyright (c) 2013-2016, Intel Corporation.
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*/
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#define pr_fmt(fmt) "efibc: " fmt
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#include <linux/efi.h>
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#include <linux/module.h>
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#include <linux/reboot.h>
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#include <linux/slab.h>
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static void efibc_str_to_str16(const char *str, efi_char16_t *str16)
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{
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size_t i;
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for (i = 0; i < strlen(str); i++)
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str16[i] = str[i];
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str16[i] = '\0';
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}
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static int efibc_set_variable(const char *name, const char *value)
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{
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int ret;
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efi_guid_t guid = LINUX_EFI_LOADER_ENTRY_GUID;
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struct efivar_entry *entry;
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size_t size = (strlen(value) + 1) * sizeof(efi_char16_t);
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if (size > sizeof(entry->var.Data)) {
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pr_err("value is too large (%zu bytes) for '%s' EFI variable\n", size, name);
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return -EINVAL;
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}
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entry = kmalloc(sizeof(*entry), GFP_KERNEL);
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if (!entry) {
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pr_err("failed to allocate efivar entry for '%s' EFI variable\n", name);
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return -ENOMEM;
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}
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efibc_str_to_str16(name, entry->var.VariableName);
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efibc_str_to_str16(value, (efi_char16_t *)entry->var.Data);
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memcpy(&entry->var.VendorGuid, &guid, sizeof(guid));
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ret = efivar_entry_set_safe(entry->var.VariableName,
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entry->var.VendorGuid,
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EFI_VARIABLE_NON_VOLATILE
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| EFI_VARIABLE_BOOTSERVICE_ACCESS
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| EFI_VARIABLE_RUNTIME_ACCESS,
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false, size, entry->var.Data);
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if (ret)
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pr_err("failed to set %s EFI variable: 0x%x\n",
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name, ret);
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kfree(entry);
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return ret;
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}
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static int efibc_reboot_notifier_call(struct notifier_block *notifier,
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unsigned long event, void *data)
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{
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const char *reason = "shutdown";
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int ret;
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if (event == SYS_RESTART)
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reason = "reboot";
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ret = efibc_set_variable("LoaderEntryRebootReason", reason);
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if (ret || !data)
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return NOTIFY_DONE;
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efibc_set_variable("LoaderEntryOneShot", (char *)data);
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return NOTIFY_DONE;
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}
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static struct notifier_block efibc_reboot_notifier = {
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.notifier_call = efibc_reboot_notifier_call,
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};
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static int __init efibc_init(void)
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{
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int ret;
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if (!efivars_kobject() || !efivar_supports_writes())
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return -ENODEV;
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ret = register_reboot_notifier(&efibc_reboot_notifier);
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if (ret)
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pr_err("unable to register reboot notifier\n");
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return ret;
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}
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module_init(efibc_init);
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static void __exit efibc_exit(void)
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{
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unregister_reboot_notifier(&efibc_reboot_notifier);
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}
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module_exit(efibc_exit);
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MODULE_AUTHOR("Jeremy Compostella <jeremy.compostella@intel.com>");
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MODULE_AUTHOR("Matt Gumbel <matthew.k.gumbel@intel.com");
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MODULE_DESCRIPTION("EFI Bootloader Control");
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MODULE_LICENSE("GPL v2");
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