efivarfs: add variable resync after hibernation

Hibernation allows other OSs to boot and thus the variable state might
be altered by the time the hibernation image is resumed.  Resync the
variable state by looping over all the dentries and update the size
(in case of alteration) delete any which no-longer exist.  Finally,
loop over all efi variables creating any which don't have
corresponding dentries.

Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
[ardb: - apply error pointer fixup from Dan Carpenter
       - rebase onto latest version of James's efivarfs rework]
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

Author: James Bottomley

fs/efivarfs/internal.h

@@ -17,6 +17,7 @@ struct efivarfs_fs_info {
 	struct efivarfs_mount_opts mount_opts;
 	struct super_block *sb;
 	struct notifier_block nb;
+	struct notifier_block pm_nb;
 };
 
 struct efi_variable {
@@ -37,7 +38,7 @@ static inline struct efivar_entry *efivar_entry(struct inode *inode)
 }
 
 int efivar_init(int (*func)(efi_char16_t *, efi_guid_t, unsigned long, void *),
-		void *data);
+		void *data, bool duplicate_check);
 
 int efivar_entry_delete(struct efivar_entry *entry);
 

fs/efivarfs/super.c

@@ -13,6 +13,7 @@
 #include <linux/pagemap.h>
 #include <linux/ucs2_string.h>
 #include <linux/slab.h>
+#include <linux/suspend.h>
 #include <linux/magic.h>
 #include <linux/statfs.h>
 #include <linux/notifier.h>
@@ -366,7 +367,7 @@ static int efivarfs_fill_super(struct super_block *sb, struct fs_context *fc)
 	if (err)
 		return err;
 
-	return efivar_init(efivarfs_callback, sb);
+	return efivar_init(efivarfs_callback, sb, true);
 }
 
 static int efivarfs_get_tree(struct fs_context *fc)
@@ -390,6 +391,148 @@ static const struct fs_context_operations efivarfs_context_ops = {
 	.reconfigure	= efivarfs_reconfigure,
 };
 
+struct efivarfs_ctx {
+	struct dir_context ctx;
+	struct super_block *sb;
+	struct dentry *dentry;
+};
+
+static bool efivarfs_actor(struct dir_context *ctx, const char *name, int len,
+			   loff_t offset, u64 ino, unsigned mode)
+{
+	unsigned long size;
+	struct efivarfs_ctx *ectx = container_of(ctx, struct efivarfs_ctx, ctx);
+	struct qstr qstr = { .name = name, .len = len };
+	struct dentry *dentry = d_hash_and_lookup(ectx->sb->s_root, &qstr);
+	struct inode *inode;
+	struct efivar_entry *entry;
+	int err;
+
+	if (IS_ERR_OR_NULL(dentry))
+		return true;
+
+	inode = d_inode(dentry);
+	entry = efivar_entry(inode);
+
+	err = efivar_entry_size(entry, &size);
+	size += sizeof(__u32);	/* attributes */
+	if (err)
+		size = 0;
+
+	inode_lock(inode);
+	i_size_write(inode, size);
+	inode_unlock(inode);
+
+	if (!size) {
+		ectx->dentry = dentry;
+		return false;
+	}
+
+	dput(dentry);
+
+	return true;
+}
+
+static int efivarfs_check_missing(efi_char16_t *name16, efi_guid_t vendor,
+				  unsigned long name_size, void *data)
+{
+	char *name;
+	struct super_block *sb = data;
+	struct dentry *dentry;
+	struct qstr qstr;
+	int err;
+
+	if (guid_equal(&vendor, &LINUX_EFI_RANDOM_SEED_TABLE_GUID))
+		return 0;
+
+	name = efivar_get_utf8name(name16, &vendor);
+	if (!name)
+		return -ENOMEM;
+
+	qstr.name = name;
+	qstr.len = strlen(name);
+	dentry = d_hash_and_lookup(sb->s_root, &qstr);
+	if (IS_ERR(dentry)) {
+		err = PTR_ERR(dentry);
+		goto out;
+	}
+
+	if (!dentry) {
+		/* found missing entry */
+		pr_info("efivarfs: creating variable %s\n", name);
+		return efivarfs_create_dentry(sb, name16, name_size, vendor, name);
+	}
+
+	dput(dentry);
+	err = 0;
+
+ out:
+	kfree(name);
+
+	return err;
+}
+
+static int efivarfs_pm_notify(struct notifier_block *nb, unsigned long action,
+			      void *ptr)
+{
+	struct efivarfs_fs_info *sfi = container_of(nb, struct efivarfs_fs_info,
+						    pm_nb);
+	struct path path = { .mnt = NULL, .dentry = sfi->sb->s_root, };
+	struct efivarfs_ctx ectx = {
+		.ctx = {
+			.actor	= efivarfs_actor,
+		},
+		.sb = sfi->sb,
+	};
+	struct file *file;
+	static bool rescan_done = true;
+
+	if (action == PM_HIBERNATION_PREPARE) {
+		rescan_done = false;
+		return NOTIFY_OK;
+	} else if (action != PM_POST_HIBERNATION) {
+		return NOTIFY_DONE;
+	}
+
+	if (rescan_done)
+		return NOTIFY_DONE;
+
+	pr_info("efivarfs: resyncing variable state\n");
+
+	/* O_NOATIME is required to prevent oops on NULL mnt */
+	file = kernel_file_open(&path, O_RDONLY | O_DIRECTORY | O_NOATIME,
+				current_cred());
+	if (IS_ERR(file))
+		return NOTIFY_DONE;
+
+	rescan_done = true;
+
+	/*
+	 * First loop over the directory and verify each entry exists,
+	 * removing it if it doesn't
+	 */
+	file->f_pos = 2;	/* skip . and .. */
+	do {
+		ectx.dentry = NULL;
+		iterate_dir(file, &ectx.ctx);
+		if (ectx.dentry) {
+			pr_info("efivarfs: removing variable %pd\n",
+				ectx.dentry);
+			simple_recursive_removal(ectx.dentry, NULL);
+			dput(ectx.dentry);
+		}
+	} while (ectx.dentry);
+	fput(file);
+
+	/*
+	 * then loop over variables, creating them if there's no matching
+	 * dentry
+	 */
+	efivar_init(efivarfs_check_missing, sfi->sb, false);
+
+	return NOTIFY_OK;
+}
+
 static int efivarfs_init_fs_context(struct fs_context *fc)
 {
 	struct efivarfs_fs_info *sfi;
@@ -406,6 +549,11 @@ static int efivarfs_init_fs_context(struct fs_context *fc)
 
 	fc->s_fs_info = sfi;
 	fc->ops = &efivarfs_context_ops;
+
+	sfi->pm_nb.notifier_call = efivarfs_pm_notify;
+	sfi->pm_nb.priority = 0;
+	register_pm_notifier(&sfi->pm_nb);
+
 	return 0;
 }
 
@@ -415,6 +563,7 @@ static void efivarfs_kill_sb(struct super_block *sb)
 
 	blocking_notifier_chain_unregister(&efivar_ops_nh, &sfi->nb);
 	kill_litter_super(sb);
+	unregister_pm_notifier(&sfi->pm_nb);
 
 	kfree(sfi);
 }

fs/efivarfs/vars.c

@@ -364,14 +364,15 @@ static void dup_variable_bug(efi_char16_t *str16, efi_guid_t *vendor_guid,
  * efivar_init - build the initial list of EFI variables
  * @func: callback function to invoke for every variable
  * @data: function-specific data to pass to @func
+ * @duplicate_check: fail if a duplicate variable is found
  *
  * Get every EFI variable from the firmware and invoke @func. @func
  * should populate the initial dentry and inode tree.
  *
  * Returns 0 on success, or a kernel error code on failure.
  */
 int efivar_init(int (*func)(efi_char16_t *, efi_guid_t, unsigned long, void *),
-		void *data)
+		void *data, bool duplicate_check)
 {
 	unsigned long variable_name_size = 512;
 	efi_char16_t *variable_name;
@@ -415,7 +416,8 @@ int efivar_init(int (*func)(efi_char16_t *, efi_guid_t, unsigned long, void *),
 			 * we'll ever see a different variable name,
 			 * and may end up looping here forever.
 			 */
-			if (efivarfs_variable_is_present(variable_name,
+			if (duplicate_check &&
+			    efivarfs_variable_is_present(variable_name,
 							 &vendor_guid, data)) {
 				dup_variable_bug(variable_name, &vendor_guid,
 						 variable_name_size);