efi: vars: Use locking version to iterate over efivars linked lists

Both efivars and efivarfs uses __efivar_entry_iter() to go over the
linked list that shadows the list of EFI variables held by the firmware,
but fail to call the begin/end helpers that are documented as a
prerequisite.

So switch to the proper version, which is efivar_entry_iter(). Given
that in both cases, efivar_entry_remove() is invoked with the lock held
already, don't take the lock there anymore.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

drivers/firmware/efi/efivars.c

@@ -602,10 +602,7 @@ static int efivars_sysfs_callback(efi_char16_t *name, efi_guid_t vendor,
 
 static int efivar_sysfs_destroy(struct efivar_entry *entry, void *data)
 {
-	int err = efivar_entry_remove(entry);
-
-	if (err)
-		return err;
+	efivar_entry_remove(entry);
 	efivar_unregister(entry);
 	return 0;
 }
@@ -615,8 +612,7 @@ static void efivars_sysfs_exit(void)
 	/* Remove all entries and destroy */
 	int err;
 
-	err = __efivar_entry_iter(efivar_sysfs_destroy, &efivar_sysfs_list,
-				  NULL, NULL);
+	err = efivar_entry_iter(efivar_sysfs_destroy, &efivar_sysfs_list, NULL);
 	if (err) {
 		pr_err("efivars: Failed to destroy sysfs entries\n");
 		return;

drivers/firmware/efi/vars.c

@@ -523,17 +523,10 @@ EXPORT_SYMBOL_GPL(__efivar_entry_add);
 /**
  * efivar_entry_remove - remove entry from variable list
  * @entry: entry to remove from list
- *
- * Returns 0 on success, or a kernel error code on failure.
  */
-int efivar_entry_remove(struct efivar_entry *entry)
+void efivar_entry_remove(struct efivar_entry *entry)
 {
-	if (down_interruptible(&efivars_lock))
-		return -EINTR;
 	list_del(&entry->list);
-	up(&efivars_lock);
-
-	return 0;
 }
 EXPORT_SYMBOL_GPL(efivar_entry_remove);
 

fs/efivarfs/super.c

@@ -180,10 +180,7 @@ static int efivarfs_callback(efi_char16_t *name16, efi_guid_t vendor,
 
 static int efivarfs_destroy(struct efivar_entry *entry, void *data)
 {
-	int err = efivar_entry_remove(entry);
-
-	if (err)
-		return err;
+	efivar_entry_remove(entry);
 	kfree(entry);
 	return 0;
 }
@@ -219,7 +216,7 @@ static int efivarfs_fill_super(struct super_block *sb, struct fs_context *fc)
 
 	err = efivar_init(efivarfs_callback, (void *)sb, true, &efivarfs_list);
 	if (err)
-		__efivar_entry_iter(efivarfs_destroy, &efivarfs_list, NULL, NULL);
+		efivar_entry_iter(efivarfs_destroy, &efivarfs_list, NULL);
 
 	return err;
 }
@@ -244,7 +241,7 @@ static void efivarfs_kill_sb(struct super_block *sb)
 	kill_litter_super(sb);
 
 	/* Remove all entries and destroy */
-	__efivar_entry_iter(efivarfs_destroy, &efivarfs_list, NULL, NULL);
+	efivar_entry_iter(efivarfs_destroy, &efivarfs_list, NULL);
 }
 
 static struct file_system_type efivarfs_type = {

include/linux/efi.h

@@ -1063,7 +1063,7 @@ int efivar_init(int (*func)(efi_char16_t *, efi_guid_t, unsigned long, void *),
 
 int efivar_entry_add(struct efivar_entry *entry, struct list_head *head);
 void __efivar_entry_add(struct efivar_entry *entry, struct list_head *head);
-int efivar_entry_remove(struct efivar_entry *entry);
+void efivar_entry_remove(struct efivar_entry *entry);
 
 int __efivar_entry_delete(struct efivar_entry *entry);
 int efivar_entry_delete(struct efivar_entry *entry);