Merge branch 'x86/urgent' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 fixes from Peter Anvin:
 "A collection of minor fixes, more EFI variables paranoia
  (anti-bricking) plus the ability to disable the pstore either as a
  runtime default or completely, due to bricking concerns."

* 'x86/urgent' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  efivars: Fix check for CONFIG_EFI_VARS_PSTORE_DEFAULT_DISABLE
  x86, microcode_intel_early: Mark apply_microcode_early() as cpuinit
  efivars: Handle duplicate names from get_next_variable()
  efivars: explicitly calculate length of VariableName
  efivars: Add module parameter to disable use as a pstore backend
  efivars: Allow disabling use as a pstore backend
  x86-32, microcode_intel_early: Fix crash with CONFIG_DEBUG_VIRTUAL
  x86-64: Fix the failure case in copy_user_handle_tail()

2 files changed, 122 insertions, 46 deletions

diff --git a/drivers/firmware/Kconfig b/drivers/firmware/Kconfig
index 9b00072a020..42c759a4d04 100644
--- a/drivers/firmware/Kconfig
+++ b/drivers/firmware/Kconfig
@@ -53,6 +53,24 @@ config EFI_VARS
 	  Subsequent efibootmgr releases may be found at:
 	  <http://linux.dell.com/efibootmgr>
 
+config EFI_VARS_PSTORE
+	bool "Register efivars backend for pstore"
+	depends on EFI_VARS && PSTORE
+	default y
+	help
+	  Say Y here to enable use efivars as a backend to pstore. This
+	  will allow writing console messages, crash dumps, or anything
+	  else supported by pstore to EFI variables.
+
+config EFI_VARS_PSTORE_DEFAULT_DISABLE
+	bool "Disable using efivars as a pstore backend by default"
+	depends on EFI_VARS_PSTORE
+	default n
+	help
+	  Saying Y here will disable the use of efivars as a storage
+	  backend for pstore by default. This setting can be overridden
+	  using the efivars module's pstore_disable parameter.
+
 config EFI_PCDP
 	bool "Console device selection via EFI PCDP or HCDP table"
 	depends on ACPI && EFI && IA64
diff --git a/drivers/firmware/efivars.c b/drivers/firmware/efivars.c
index fe62aa39223..7acafb80fd4 100644
--- a/drivers/firmware/efivars.c
+++ b/drivers/firmware/efivars.c
@@ -103,6 +103,11 @@ MODULE_VERSION(EFIVARS_VERSION);
  */
 #define GUID_LEN 36
 
+static bool efivars_pstore_disable =
+	IS_ENABLED(CONFIG_EFI_VARS_PSTORE_DEFAULT_DISABLE);
+
+module_param_named(pstore_disable, efivars_pstore_disable, bool, 0644);
+
 /*
  * The maximum size of VariableName + Data = 1024
  * Therefore, it's reasonable to save that much
@@ -165,6 +170,7 @@ efivar_create_sysfs_entry(struct efivars *efivars,
 
 static void efivar_update_sysfs_entries(struct work_struct *);
 static DECLARE_WORK(efivar_work, efivar_update_sysfs_entries);
+static bool efivar_wq_enabled = true;
 
 /* Return the number of unicode characters in data */
 static unsigned long
@@ -1309,9 +1315,7 @@ static const struct inode_operations efivarfs_dir_inode_operations = {
 	.create = efivarfs_create,
 };
 
-static struct pstore_info efi_pstore_info;
-
-#ifdef CONFIG_PSTORE
+#ifdef CONFIG_EFI_VARS_PSTORE
 
 static int efi_pstore_open(struct pstore_info *psi)
 {
@@ -1441,7 +1445,7 @@ static int efi_pstore_write(enum pstore_type_id type,
 
 	spin_unlock_irqrestore(&efivars->lock, flags);
 
-	if (reason == KMSG_DUMP_OOPS)
+	if (reason == KMSG_DUMP_OOPS && efivar_wq_enabled)
 		schedule_work(&efivar_work);
 
 	*id = part;
@@ -1514,38 +1518,6 @@ static int efi_pstore_erase(enum pstore_type_id type, u64 id, int count,
 
 	return 0;
 }
-#else
-static int efi_pstore_open(struct pstore_info *psi)
-{
-	return 0;
-}
-
-static int efi_pstore_close(struct pstore_info *psi)
-{
-	return 0;
-}
-
-static ssize_t efi_pstore_read(u64 *id, enum pstore_type_id *type, int *count,
-			       struct timespec *timespec,
-			       char **buf, struct pstore_info *psi)
-{
-	return -1;
-}
-
-static int efi_pstore_write(enum pstore_type_id type,
-		enum kmsg_dump_reason reason, u64 *id,
-		unsigned int part, int count, size_t size,
-		struct pstore_info *psi)
-{
-	return 0;
-}
-
-static int efi_pstore_erase(enum pstore_type_id type, u64 id, int count,
-			    struct timespec time, struct pstore_info *psi)
-{
-	return 0;
-}
-#endif
 
 static struct pstore_info efi_pstore_info = {
 	.owner		= THIS_MODULE,
@@ -1557,6 +1529,24 @@ static struct pstore_info efi_pstore_info = {
 	.erase		= efi_pstore_erase,
 };
 
+static void efivar_pstore_register(struct efivars *efivars)
+{
+	efivars->efi_pstore_info = efi_pstore_info;
+	efivars->efi_pstore_info.buf = kmalloc(4096, GFP_KERNEL);
+	if (efivars->efi_pstore_info.buf) {
+		efivars->efi_pstore_info.bufsize = 1024;
+		efivars->efi_pstore_info.data = efivars;
+		spin_lock_init(&efivars->efi_pstore_info.buf_lock);
+		pstore_register(&efivars->efi_pstore_info);
+	}
+}
+#else
+static void efivar_pstore_register(struct efivars *efivars)
+{
+	return;
+}
+#endif
+
 static ssize_t efivar_create(struct file *filp, struct kobject *kobj,
 			     struct bin_attribute *bin_attr,
 			     char *buf, loff_t pos, size_t count)
@@ -1716,6 +1706,31 @@ static bool variable_is_present(efi_char16_t *variable_name, efi_guid_t *vendor)
 	return found;
 }
 
+/*
+ * Returns the size of variable_name, in bytes, including the
+ * terminating NULL character, or variable_name_size if no NULL
+ * character is found among the first variable_name_size bytes.
+ */
+static unsigned long var_name_strnsize(efi_char16_t *variable_name,
+				       unsigned long variable_name_size)
+{
+	unsigned long len;
+	efi_char16_t c;
+
+	/*
+	 * The variable name is, by definition, a NULL-terminated
+	 * string, so make absolutely sure that variable_name_size is
+	 * the value we expect it to be. If not, return the real size.
+	 */
+	for (len = 2; len <= variable_name_size; len += sizeof(c)) {
+		c = variable_name[(len / sizeof(c)) - 1];
+		if (!c)
+			break;
+	}
+
+	return min(len, variable_name_size);
+}
+
 static void efivar_update_sysfs_entries(struct work_struct *work)
 {
 	struct efivars *efivars = &__efivars;
@@ -1756,10 +1771,13 @@ static void efivar_update_sysfs_entries(struct work_struct *work)
 		if (!found) {
 			kfree(variable_name);
 			break;
-		} else
+		} else {
+			variable_name_size = var_name_strnsize(variable_name,
+							       variable_name_size);
 			efivar_create_sysfs_entry(efivars,
 						  variable_name_size,
 						  variable_name, &vendor);
+		}
 	}
 }
 
@@ -1958,6 +1976,35 @@ void unregister_efivars(struct efivars *efivars)
 }
 EXPORT_SYMBOL_GPL(unregister_efivars);
 
+/*
+ * Print a warning when duplicate EFI variables are encountered and
+ * disable the sysfs workqueue since the firmware is buggy.
+ */
+static void dup_variable_bug(efi_char16_t *s16, efi_guid_t *vendor_guid,
+			     unsigned long len16)
+{
+	size_t i, len8 = len16 / sizeof(efi_char16_t);
+	char *s8;
+
+	/*
+	 * Disable the workqueue since the algorithm it uses for
+	 * detecting new variables won't work with this buggy
+	 * implementation of GetNextVariableName().
+	 */
+	efivar_wq_enabled = false;
+
+	s8 = kzalloc(len8, GFP_KERNEL);
+	if (!s8)
+		return;
+
+	for (i = 0; i < len8; i++)
+		s8[i] = s16[i];
+
+	printk(KERN_WARNING "efivars: duplicate variable: %s-%pUl\n",
+	       s8, vendor_guid);
+	kfree(s8);
+}
+
 int register_efivars(struct efivars *efivars,
 		     const struct efivar_operations *ops,
 		     struct kobject *parent_kobj)
@@ -2006,6 +2053,24 @@ int register_efivars(struct efivars *efivars,
 						&vendor_guid);
 		switch (status) {
 		case EFI_SUCCESS:
+			variable_name_size = var_name_strnsize(variable_name,
+							       variable_name_size);
+
+			/*
+			 * Some firmware implementations return the
+			 * same variable name on multiple calls to
+			 * get_next_variable(). Terminate the loop
+			 * immediately as there is no guarantee that
+			 * we'll ever see a different variable name,
+			 * and may end up looping here forever.
+			 */
+			if (variable_is_present(variable_name, &vendor_guid)) {
+				dup_variable_bug(variable_name, &vendor_guid,
+						 variable_name_size);
+				status = EFI_NOT_FOUND;
+				break;
+			}
+
 			efivar_create_sysfs_entry(efivars,
 						  variable_name_size,
 						  variable_name,
@@ -2025,15 +2090,8 @@ int register_efivars(struct efivars *efivars,
 	if (error)
 		unregister_efivars(efivars);
 
-	efivars->efi_pstore_info = efi_pstore_info;
-
-	efivars->efi_pstore_info.buf = kmalloc(4096, GFP_KERNEL);
-	if (efivars->efi_pstore_info.buf) {
-		efivars->efi_pstore_info.bufsize = 1024;
-		efivars->efi_pstore_info.data = efivars;
-		spin_lock_init(&efivars->efi_pstore_info.buf_lock);
-		pstore_register(&efivars->efi_pstore_info);
-	}
+	if (!efivars_pstore_disable)
+		efivar_pstore_register(efivars);
 
 	register_filesystem(&efivarfs_type);