2 files changed, 122 insertions, 46 deletions

diff --git a/drivers/firmware/Kconfig b/drivers/firmware/Kconfig
index 9b00072a020f..42c759a4d047 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 fe62aa392239..7acafb80fd4c 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);