[PATCH 00/25] fscrypt: add some higher-level helper functions

@@ -4589,10 +4589,13 @@ void ext4_set_inode_flags(struct inode *inode)
 		new_fl |= S_DIRSYNC;
 	if (test_opt(inode->i_sb, DAX) && S_ISREG(inode->i_mode) &&
 	    !ext4_should_journal_data(inode) && !ext4_has_inline_data(inode) &&
-	    !ext4_encrypted_inode(inode))
+	    !(flags & EXT4_ENCRYPT_FL))
 		new_fl |= S_DAX;
+	if (flags & EXT4_ENCRYPT_FL)
+		new_fl |= S_ENCRYPTED;
 	inode_set_flags(inode, new_fl,
-			S_SYNC|S_APPEND|S_IMMUTABLE|S_NOATIME|S_DIRSYNC|S_DAX);
+			S_SYNC|S_APPEND|S_IMMUTABLE|S_NOATIME|S_DIRSYNC|S_DAX|
+			S_ENCRYPTED);
 }
 
 static blkcnt_t ext4_inode_blocks(struct ext4_inode *raw_inode,

@@ -1181,7 +1181,8 @@ static int ext4_set_context(struct inode *inode, const void *ctx, size_t len,
 			ext4_clear_inode_state(inode,
 					EXT4_STATE_MAY_INLINE_DATA);
 			/*
-			 * Update inode->i_flags - e.g. S_DAX may get disabled
+			 * Update inode->i_flags - S_ENCRYPTED will be enabled,
+			 * S_DAX may be disabled
 			 */
 			ext4_set_inode_flags(inode);
 		}

@@ -1206,7 +1207,10 @@ static int ext4_set_context(struct inode *inode, const void *ctx, size_t len,
 				    ctx, len, 0);
 	if (!res) {
 		ext4_set_inode_flag(inode, EXT4_INODE_ENCRYPT);
-		/* Update inode->i_flags - e.g. S_DAX may get disabled */
+		/*
+		 * Update inode->i_flags - S_ENCRYPTED will be enabled,
+		 * S_DAX may be disabled
+		 */
 		ext4_set_inode_flags(inode);
 		res = ext4_mark_inode_dirty(handle, inode);
 		if (res)

@@ -2949,6 +2949,7 @@ static inline void f2fs_set_encrypted_inode(struct inode *inode)
 {
 #ifdef CONFIG_F2FS_FS_ENCRYPTION
 	file_set_encrypt(inode);
+	inode->i_flags |= S_ENCRYPTED;
 #endif
 }
 

@@ -43,8 +43,11 @@ void f2fs_set_inode_flags(struct inode *inode)
 		new_fl |= S_NOATIME;
 	if (flags & FS_DIRSYNC_FL)
 		new_fl |= S_DIRSYNC;
+	if (f2fs_encrypted_inode(inode))
+		new_fl |= S_ENCRYPTED;
 	inode_set_flags(inode, new_fl,
-			S_SYNC|S_APPEND|S_IMMUTABLE|S_NOATIME|S_DIRSYNC);
+			S_SYNC|S_APPEND|S_IMMUTABLE|S_NOATIME|S_DIRSYNC|
+			S_ENCRYPTED);
 }
 
 static void __get_inode_rdev(struct inode *inode, struct f2fs_inode *ri)

@@ -38,7 +38,8 @@ void ubifs_set_inode_flags(struct inode *inode)
 {
 	unsigned int flags = ubifs_inode(inode)->flags;
 
-	inode->i_flags &= ~(S_SYNC | S_APPEND | S_IMMUTABLE | S_DIRSYNC);
+	inode->i_flags &= ~(S_SYNC | S_APPEND | S_IMMUTABLE | S_DIRSYNC |
+			    S_ENCRYPTED);
 	if (flags & UBIFS_SYNC_FL)
 		inode->i_flags |= S_SYNC;
 	if (flags & UBIFS_APPEND_FL)

@@ -47,6 +48,8 @@ void ubifs_set_inode_flags(struct inode *inode)
 		inode->i_flags |= S_IMMUTABLE;
 	if (flags & UBIFS_DIRSYNC_FL)
 		inode->i_flags |= S_DIRSYNC;
+	if (flags & UBIFS_CRYPT_FL)
+		inode->i_flags |= S_ENCRYPTED;
 }
 
 /*

@@ -170,6 +170,7 @@ static int create_xattr(struct ubifs_info *c, struct inode *host,
 	err = ubifs_jnl_update(c, host, nm, inode, 0, 1);
 	if (err)
 		goto out_cancel;
+	ubifs_set_inode_flags(host);
 	mutex_unlock(&host_ui->ui_mutex);
 
 	ubifs_release_budget(c, &req);

@@ -1853,6 +1853,7 @@ struct super_operations {
 #else
 #define S_DAX		0	/* Make all the DAX code disappear */
 #endif
+#define S_ENCRYPTED	16384	/* Encrypted file (using fs/crypto/) */
 
 /*
  * Note that nosuid etc flags are inode-specific: setting some file-system

@@ -1892,6 +1893,7 @@ static inline bool sb_rdonly(const struct super_block *sb) { return sb->s_flags
 #define IS_AUTOMOUNT(inode)	((inode)->i_flags & S_AUTOMOUNT)
 #define IS_NOSEC(inode)		((inode)->i_flags & S_NOSEC)
 #define IS_DAX(inode)		((inode)->i_flags & S_DAX)
+#define IS_ENCRYPTED(inode)	((inode)->i_flags & S_ENCRYPTED)
 
 #define IS_WHITEOUT(inode)	(S_ISCHR(inode->i_mode) && \
 				 (inode)->i_rdev == WHITEOUT_DEV)

@@ -340,7 +340,7 @@ static int fscrypt_d_revalidate(struct dentry *dentry, unsigned int flags)
 		return -ECHILD;
 
 	dir = dget_parent(dentry);
-	if (!d_inode(dir)->i_sb->s_cop->is_encrypted(d_inode(dir))) {
+	if (!IS_ENCRYPTED(d_inode(dir))) {
 		dput(dir);
 		return 0;
 	}

@@ -382,8 +382,7 @@ int fscrypt_setup_filename(struct inode *dir, const struct qstr *iname,
 	memset(fname, 0, sizeof(struct fscrypt_name));
 	fname->usr_fname = iname;
 
-	if (!dir->i_sb->s_cop->is_encrypted(dir) ||
-				fscrypt_is_dot_dotdot(iname)) {
+	if (!IS_ENCRYPTED(dir) || fscrypt_is_dot_dotdot(iname)) {
 		fname->disk_name.name = (unsigned char *)iname->name;
 		fname->disk_name.len = iname->len;
 		return 0;

@@ -268,7 +268,7 @@ int fscrypt_get_encryption_info(struct inode *inode)
 	res = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx));
 	if (res < 0) {
 		if (!fscrypt_dummy_context_enabled(inode) ||
-		    inode->i_sb->s_cop->is_encrypted(inode))
+		    IS_ENCRYPTED(inode))
 			return res;
 		/* Fake up a context for an unencrypted directory */
 		memset(&ctx, 0, sizeof(ctx));

@@ -109,7 +109,7 @@ int fscrypt_ioctl_get_policy(struct file *filp, void __user *arg)
 	struct fscrypt_policy policy;
 	int res;
 
-	if (!inode->i_sb->s_cop->is_encrypted(inode))
+	if (!IS_ENCRYPTED(inode))
 		return -ENODATA;
 
 	res = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx));

@@ -166,11 +166,11 @@ int fscrypt_has_permitted_context(struct inode *parent, struct inode *child)
 		return 1;
 
 	/* No restrictions if the parent directory is unencrypted */
-	if (!cops->is_encrypted(parent))
+	if (!IS_ENCRYPTED(parent))
 		return 1;
 
 	/* Encrypted directories must not contain unencrypted files */
-	if (!cops->is_encrypted(child))
+	if (!IS_ENCRYPTED(child))
 		return 0;
 
 	/*

@@ -97,7 +97,7 @@ static inline int fscrypt_setup_filename(struct inode *dir,
 					 const struct qstr *iname,
 					 int lookup, struct fscrypt_name *fname)
 {
-	if (dir->i_sb->s_cop->is_encrypted(dir))
+	if (IS_ENCRYPTED(dir))
 		return -EOPNOTSUPP;
 
 	memset(fname, 0, sizeof(struct fscrypt_name));

@@ -1241,13 +1241,11 @@ static const struct fscrypt_operations ext4_cryptops = {
 	.get_context		= ext4_get_context,
 	.set_context		= ext4_set_context,
 	.dummy_context		= ext4_dummy_context,
-	.is_encrypted		= ext4_encrypted_inode,
 	.empty_dir		= ext4_empty_dir,
 	.max_namelen		= ext4_max_namelen,
 };
 #else
 static const struct fscrypt_operations ext4_cryptops = {
-	.is_encrypted		= ext4_encrypted_inode,
 };
 #endif
 

@@ -1594,13 +1594,11 @@ static const struct fscrypt_operations f2fs_cryptops = {
 	.key_prefix	= "f2fs:",
 	.get_context	= f2fs_get_context,
 	.set_context	= f2fs_set_context,
-	.is_encrypted	= f2fs_encrypted_inode,
 	.empty_dir	= f2fs_empty_dir,
 	.max_namelen	= f2fs_max_namelen,
 };
 #else
 static const struct fscrypt_operations f2fs_cryptops = {
-	.is_encrypted	= f2fs_encrypted_inode,
 };
 #endif
 

@@ -87,7 +87,6 @@ const struct fscrypt_operations ubifs_crypt_operations = {
 	.key_prefix		= "ubifs:",
 	.get_context		= ubifs_crypt_get_context,
 	.set_context		= ubifs_crypt_set_context,
-	.is_encrypted		= __ubifs_crypt_is_encrypted,
 	.empty_dir		= ubifs_crypt_empty_dir,
 	.max_namelen		= ubifs_crypt_max_namelen,
 };

@@ -2009,7 +2009,6 @@ static struct ubifs_info *alloc_ubifs_info(struct ubi_volume_desc *ubi)
 
 #ifndef CONFIG_UBIFS_FS_ENCRYPTION
 const struct fscrypt_operations ubifs_crypt_operations = {
-	.is_encrypted		= __ubifs_crypt_is_encrypted,
 };
 #endif
 

@@ -1835,18 +1835,13 @@ int ubifs_decrypt(const struct inode *inode, struct ubifs_data_node *dn,
 
 extern const struct fscrypt_operations ubifs_crypt_operations;
 
-static inline bool __ubifs_crypt_is_encrypted(struct inode *inode)
+static inline bool ubifs_crypt_is_encrypted(const struct inode *inode)
 {
-	struct ubifs_inode *ui = ubifs_inode(inode);
+	const struct ubifs_inode *ui = ubifs_inode(inode);
 
 	return ui->flags & UBIFS_CRYPT_FL;
 }
 
-static inline bool ubifs_crypt_is_encrypted(const struct inode *inode)
-{
-	return __ubifs_crypt_is_encrypted((struct inode *)inode);
-}

@@ -1244,9 +1244,6 @@ static const struct fscrypt_operations ext4_cryptops = {
 	.empty_dir		= ext4_empty_dir,
 	.max_namelen		= ext4_max_namelen,
 };
-#else
-static const struct fscrypt_operations ext4_cryptops = {
-};
 #endif
 
 #ifdef CONFIG_QUOTA

@@ -3998,7 +3995,9 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
 	sb->s_op = &ext4_sops;
 	sb->s_export_op = &ext4_export_ops;
 	sb->s_xattr = ext4_xattr_handlers;
+#ifdef CONFIG_EXT4_FS_ENCRYPTION
 	sb->s_cop = &ext4_cryptops;
+#endif
 #ifdef CONFIG_QUOTA
 	sb->dq_op = &ext4_quota_operations;
 	if (ext4_has_feature_quota(sb))

@@ -1597,9 +1597,6 @@ static const struct fscrypt_operations f2fs_cryptops = {
 	.empty_dir	= f2fs_empty_dir,
 	.max_namelen	= f2fs_max_namelen,
 };
-#else
-static const struct fscrypt_operations f2fs_cryptops = {
-};
 #endif
 
 static struct inode *f2fs_nfs_get_inode(struct super_block *sb,

@@ -2318,7 +2315,9 @@ static int f2fs_fill_super(struct super_block *sb, void *data, int silent)
 #endif
 
 	sb->s_op = &f2fs_sops;
+#ifdef CONFIG_F2FS_FS_ENCRYPTION
 	sb->s_cop = &f2fs_cryptops;
+#endif
 	sb->s_xattr = f2fs_xattr_handlers;
 	sb->s_export_op = &f2fs_export_ops;
 	sb->s_magic = F2FS_SUPER_MAGIC;

@@ -2007,11 +2007,6 @@ static struct ubifs_info *alloc_ubifs_info(struct ubi_volume_desc *ubi)
 	return c;
 }
 
-#ifndef CONFIG_UBIFS_FS_ENCRYPTION
-const struct fscrypt_operations ubifs_crypt_operations = {
-};
-#endif
-
 static int ubifs_fill_super(struct super_block *sb, void *data, int silent)
 {
 	struct ubifs_info *c = sb->s_fs_info;

@@ -2054,7 +2049,9 @@ static int ubifs_fill_super(struct super_block *sb, void *data, int silent)
 		sb->s_maxbytes = c->max_inode_sz = MAX_LFS_FILESIZE;
 	sb->s_op = &ubifs_super_operations;
 	sb->s_xattr = ubifs_xattr_handlers;
+#ifdef CONFIG_UBIFS_FS_ENCRYPTION
 	sb->s_cop = &ubifs_crypt_operations;
+#endif
 
 	mutex_lock(&c->umount_mutex);
 	err = mount_ubifs(c);

@@ -174,4 +174,12 @@ static inline int fscrypt_zeroout_range(const struct inode *inode, pgoff_t lblk,
 	return -EOPNOTSUPP;
 }
 
+/* hooks.c */
+static inline int fscrypt_require_key(struct inode *inode)
+{
+	if (IS_ENCRYPTED(inode))
+		return -EOPNOTSUPP;
+	return 0;
+}
+
 #endif	/* _LINUX_FSCRYPT_NOTSUPP_H */

@@ -142,4 +142,32 @@ extern void fscrypt_pullback_bio_page(struct page **, bool);
 extern int fscrypt_zeroout_range(const struct inode *, pgoff_t, sector_t,
 				 unsigned int);
 
+/* hooks.c */
+
+/**
+ * fscrypt_require_key - require an inode's encryption key
+ * @inode: the inode we need the key for
+ *
+ * If the inode is encrypted, set up its encryption key if not already done.
+ * Then require that the key be present and return -ENOKEY otherwise.
+ *
+ * No locks are needed, and currently the key will live as long as the struct
+ * inode --- so it won't go away from under you.
+ *
+ * Return: 0 on success, -ENOKEY if the key is missing, or another -errno code
+ * if a problem occurred while setting up the encryption key.
+ */
+static inline int fscrypt_require_key(struct inode *inode)
+{
+	if (IS_ENCRYPTED(inode)) {
+		int err = fscrypt_get_encryption_info(inode);
+
+		if (err)
+			return err;
+		if (!fscrypt_has_encryption_key(inode))
+			return -ENOKEY;
+	}
+	return 0;
+}
+
 #endif	/* _LINUX_FSCRYPT_SUPP_H */

@@ -1,4 +1,4 @@
 obj-$(CONFIG_FS_ENCRYPTION)	+= fscrypto.o
 
-fscrypto-y := crypto.o fname.o policy.o keyinfo.o
+fscrypto-y := crypto.o fname.o hooks.o keyinfo.o policy.o
 fscrypto-$(CONFIG_BLOCK) += bio.o

@@ -0,0 +1,49 @@
+/*
+ * fs/crypto/hooks.c
+ *
+ * Encryption hooks for higher-level filesystem operations.
+ */
+
+#include <linux/ratelimit.h>
+#include "fscrypt_private.h"
+
+/**
+ * fscrypt_file_open - prepare to open a possibly-encrypted regular file
+ * @inode: the inode being opened
+ * @filp: the struct file being set up
+ *
+ * Currently, an encrypted regular file can only be opened if its encryption key
+ * is available; access to the raw encrypted contents is not supported.
+ * Therefore, we first set up the inode's encryption key (if not already done)
+ * and return an error if it's unavailable.
+ *
+ * We also verify that if the parent directory (from the path via which the file
+ * is being opened) is encrypted, then the inode being opened uses the same
+ * encryption policy.  This is needed as part of the enforcement that all files
+ * in an encrypted directory tree use the same encryption policy, as a
+ * protection against certain types of offline attacks.  Note that this check is
+ * needed even when opening an *unencrypted* file, since it's forbidden to have
+ * an unencrypted file in an encrypted directory.
+ *
+ * Return: 0 on success, -ENOKEY if the key is missing, or another -errno code
+ */
+int fscrypt_file_open(struct inode *inode, struct file *filp)
+{
+	int err;
+	struct dentry *dir;
+
+	err = fscrypt_require_key(inode);
+	if (err)
+		return err;
+
+	dir = dget_parent(file_dentry(filp));
+	if (IS_ENCRYPTED(d_inode(dir)) &&
+	    !fscrypt_has_permitted_context(d_inode(dir), inode)) {
+		pr_warn_ratelimited("fscrypt: inconsistent encryption contexts: %lu/%lu",
+				    d_inode(dir)->i_ino, inode->i_ino);
+		err = -EPERM;
+	}
+	dput(dir);
+	return err;
+}
+EXPORT_SYMBOL_GPL(fscrypt_file_open);

@@ -182,4 +182,11 @@ static inline int fscrypt_require_key(struct inode *inode)
 	return 0;
 }
 
+static inline int fscrypt_file_open(struct inode *inode, struct file *filp)
+{
+	if (IS_ENCRYPTED(inode))
+		return -EOPNOTSUPP;
+	return 0;
+}
+
 #endif	/* _LINUX_FSCRYPT_NOTSUPP_H */

@@ -170,4 +170,6 @@ static inline int fscrypt_require_key(struct inode *inode)
 	return 0;
 }
 
+extern int fscrypt_file_open(struct inode *inode, struct file *filp);
+
 #endif	/* _LINUX_FSCRYPT_SUPP_H */

@@ -47,3 +47,18 @@ int fscrypt_file_open(struct inode *inode, struct file *filp)
 	return err;
 }
 EXPORT_SYMBOL_GPL(fscrypt_file_open);
+
+int __fscrypt_prepare_link(struct inode *inode, struct inode *dir)
+{
+	int err;
+
+	err = fscrypt_require_key(dir);
+	if (err)
+		return err;
+
+	if (!fscrypt_has_permitted_context(dir, inode))
+		return -EPERM;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(__fscrypt_prepare_link);

@@ -189,4 +189,13 @@ static inline int fscrypt_file_open(struct inode *inode, struct file *filp)
 	return 0;
 }
 
+static inline int fscrypt_prepare_link(struct dentry *old_dentry,
+				       struct inode *dir,
+				       struct dentry *dentry)
+{
+	if (IS_ENCRYPTED(dir))
+		return -EOPNOTSUPP;
+	return 0;
+}
+
 #endif	/* _LINUX_FSCRYPT_NOTSUPP_H */

@@ -172,4 +172,33 @@ static inline int fscrypt_require_key(struct inode *inode)
 
 extern int fscrypt_file_open(struct inode *inode, struct file *filp);
 
+extern int __fscrypt_prepare_link(struct inode *inode, struct inode *dir);
+
+/**
+ * fscrypt_prepare_link - prepare to link an inode into a possibly-encrypted directory
+ * @old_dentry: an existing dentry for the inode being linked
+ * @dir: the target directory
+ * @dentry: negative dentry for the target filename
+ *
+ * A new link can only be added to an encrypted directory if the directory's
+ * encryption key is available --- since otherwise we'd have no way to encrypt
+ * the filename.  Therefore, we first set up the directory's encryption key (if
+ * not already done) and return an error if it's unavailable.
+ *
+ * We also verify that the link will not violate the constraint that all files
+ * in an encrypted directory tree use the same encryption policy.
+ *
+ * Return: 0 on success, -ENOKEY if the directory's encryption key is missing,
+ * -EPERM if the link would result in an inconsistent encryption policy, or
+ * another -errno code.
+ */
+static inline int fscrypt_prepare_link(struct dentry *old_dentry,
+				       struct inode *dir,
+				       struct dentry *dentry)
+{
+	if (IS_ENCRYPTED(dir))
+		return __fscrypt_prepare_link(d_inode(old_dentry), dir);
+	return 0;
+}
+
 #endif	/* _LINUX_FSCRYPT_SUPP_H */

@@ -62,3 +62,33 @@ int __fscrypt_prepare_link(struct inode *inode, struct inode *dir)
 	return 0;
 }
 EXPORT_SYMBOL_GPL(__fscrypt_prepare_link);
+
+int __fscrypt_prepare_rename(struct inode *old_dir, struct dentry *old_dentry,
+			     struct inode *new_dir, struct dentry *new_dentry,
+			     unsigned int flags)
+{
+	int err;
+
+	err = fscrypt_require_key(old_dir);
+	if (err)
+		return err;
+
+	err = fscrypt_require_key(new_dir);
+	if (err)
+		return err;
+
+	if (old_dir != new_dir) {
+		if (IS_ENCRYPTED(new_dir) &&
+		    !fscrypt_has_permitted_context(new_dir,
+						   d_inode(old_dentry)))
+			return -EPERM;
+
+		if ((flags & RENAME_EXCHANGE) &&
+		    IS_ENCRYPTED(old_dir) &&
+		    !fscrypt_has_permitted_context(old_dir,
+						   d_inode(new_dentry)))
+			return -EPERM;
+	}
+	return 0;
+}
+EXPORT_SYMBOL_GPL(__fscrypt_prepare_rename);

@@ -198,4 +198,15 @@ static inline int fscrypt_prepare_link(struct dentry *old_dentry,
 	return 0;
 }
 
+static inline int fscrypt_prepare_rename(struct inode *old_dir,
+					 struct dentry *old_dentry,
+					 struct inode *new_dir,
+					 struct dentry *new_dentry,
+					 unsigned int flags)
+{
+	if (IS_ENCRYPTED(old_dir) || IS_ENCRYPTED(new_dir))
+		return -EOPNOTSUPP;
+	return 0;
+}
+
 #endif	/* _LINUX_FSCRYPT_NOTSUPP_H */

@@ -201,4 +201,43 @@ static inline int fscrypt_prepare_link(struct dentry *old_dentry,
 	return 0;
 }
 
+extern int __fscrypt_prepare_rename(struct inode *old_dir,
+				    struct dentry *old_dentry,
+				    struct inode *new_dir,
+				    struct dentry *new_dentry,
+				    unsigned int flags);
+
+/**
+ * fscrypt_prepare_rename - prepare for a rename between possibly-encrypted directories
+ * @old_dir: source directory
+ * @old_dentry: dentry for source file
+ * @new_dir: target directory
+ * @new_dentry: dentry for target location (may be negative unless exchanging)
+ * @flags: rename flags (we care at least about %RENAME_EXCHANGE)
+ *
+ * Prepare for ->rename() where the source and/or target directories may be
+ * encrypted.  A new link can only be added to an encrypted directory if the
+ * directory's encryption key is available --- since otherwise we'd have no way
+ * to encrypt the filename.  A rename to an existing name, on the other hand,
+ * *is* cryptographically possible without the key.  However, we take the more
+ * conservative approach and just forbid all no-key renames.
+ *
+ * We also verify that the rename will not violate the constraint that all files
+ * in an encrypted directory tree use the same encryption policy.
+ *
+ * Return: 0 on success, -ENOKEY if an encryption key is missing, -EPERM if the
+ * rename would cause inconsistent encryption policies, or another -errno code.
+ */
+static inline int fscrypt_prepare_rename(struct inode *old_dir,
+					 struct dentry *old_dentry,
+					 struct inode *new_dir,
+					 struct dentry *new_dentry,
+					 unsigned int flags)
+{
+	if (IS_ENCRYPTED(old_dir) || IS_ENCRYPTED(new_dir))
+		return __fscrypt_prepare_rename(old_dir, old_dentry,
+						new_dir, new_dentry, flags);
+	return 0;
+}
+
 #endif	/* _LINUX_FSCRYPT_SUPP_H */

@@ -92,3 +92,21 @@ int __fscrypt_prepare_rename(struct inode *old_dir, struct dentry *old_dentry,
 	return 0;
 }
 EXPORT_SYMBOL_GPL(__fscrypt_prepare_rename);
+
+int __fscrypt_prepare_lookup(struct inode *dir, struct dentry *dentry)
+{
+	int err = fscrypt_get_encryption_info(dir);
+
+	if (err)
+		return err;
+
+	if (fscrypt_has_encryption_key(dir)) {
+		spin_lock(&dentry->d_lock);
+		dentry->d_flags |= DCACHE_ENCRYPTED_WITH_KEY;
+		spin_unlock(&dentry->d_lock);
+	}
+
+	d_set_d_op(dentry, &fscrypt_d_ops);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(__fscrypt_prepare_lookup);

@@ -209,4 +209,13 @@ static inline int fscrypt_prepare_rename(struct inode *old_dir,
 	return 0;
 }
 
+static inline int fscrypt_prepare_lookup(struct inode *dir,
+					 struct dentry *dentry,
+					 unsigned int flags)
+{
+	if (IS_ENCRYPTED(dir))
+		return -EOPNOTSUPP;
+	return 0;
+}
+
 #endif	/* _LINUX_FSCRYPT_NOTSUPP_H */

@@ -240,4 +240,34 @@ static inline int fscrypt_prepare_rename(struct inode *old_dir,
 	return 0;
 }
 
+extern int __fscrypt_prepare_lookup(struct inode *dir, struct dentry *dentry);
+
+/**
+ * fscrypt_prepare_lookup - prepare to lookup a name in a possibly-encrypted directory
+ * @dir: directory being searched
+ * @dentry: filename being looked up
+ * @flags: lookup flags
+ *
+ * Prepare for ->lookup() in a directory which may be encrypted.  Lookups can be
+ * done with or without the directory's encryption key; without the key,
+ * filenames are presented in encrypted form.  Therefore, we'll try to set up
+ * the directory's encryption key, but even without it the lookup can continue.
+ *
+ * To allow invalidating stale dentries if the directory's encryption key is
+ * added later, we also install a custom ->d_revalidate() method and use the
+ * DCACHE_ENCRYPTED_WITH_KEY flag to indicate whether a given dentry is a
+ * plaintext name (flag set) or a ciphertext name (flag cleared).
+ *
+ * Return: 0 on success, -errno if a problem occurred while setting up the
+ * encryption key
+ */
+static inline int fscrypt_prepare_lookup(struct inode *dir,
+					 struct dentry *dentry,
+					 unsigned int flags)
+{
+	if (IS_ENCRYPTED(dir))
+		return __fscrypt_prepare_lookup(dir, dentry);
+	return 0;
+}
+
 #endif	/* _LINUX_FSCRYPT_SUPP_H */

@@ -218,4 +218,12 @@ static inline int fscrypt_prepare_lookup(struct inode *dir,
 	return 0;
 }
 
+static inline int fscrypt_prepare_setattr(struct dentry *dentry,
+					  struct iattr *attr)
+{
+	if (IS_ENCRYPTED(d_inode(dentry)) && (attr->ia_valid & ATTR_SIZE))
+		return -EOPNOTSUPP;
+	return 0;
+}
+
 #endif	/* _LINUX_FSCRYPT_NOTSUPP_H */

@@ -270,4 +270,29 @@ static inline int fscrypt_prepare_lookup(struct inode *dir,
 	return 0;
 }
 
+/**
+ * fscrypt_prepare_setattr - prepare to change a possibly-encrypted inode's attributes
+ * @dentry: dentry through which the inode is being changed
+ * @attr: attributes to change
+ *
+ * Prepare for ->setattr() on a possibly-encrypted inode.  On an encrypted file,
+ * most attribute changes are allowed even without the encryption key.  However,
+ * without the encryption key we do have to forbid truncates.  This is needed
+ * because the size being truncated to may not be a multiple of the filesystem
+ * block size, and in that case we'd have to decrypt the final block, zero the
+ * portion past i_size, and re-encrypt it.  (We *could* allow truncating to a
+ * filesystem block boundary, but it's simpler to just forbid all truncates ---
+ * and we already forbid all other contents modifications without the key.)
+ *
+ * Return: 0 on success, -ENOKEY if the key is missing, or another -errno code
+ * if a problem occurred while setting up the encryption key.
+ */
+static inline int fscrypt_prepare_setattr(struct dentry *dentry,
+					  struct iattr *attr)
+{
+	if (IS_ENCRYPTED(d_inode(dentry)) && (attr->ia_valid & ATTR_SIZE))
+		return fscrypt_require_key(d_inode(dentry));
+	return 0;
+}
+
 #endif	/* _LINUX_FSCRYPT_SUPP_H */

@@ -364,7 +364,6 @@ static int ext4_file_open(struct inode * inode, struct file * filp)
 	struct super_block *sb = inode->i_sb;
 	struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
 	struct vfsmount *mnt = filp->f_path.mnt;
-	struct dentry *dir;
 	struct path path;
 	char buf[64], *cp;
 	int ret;

@@ -404,25 +403,11 @@ static int ext4_file_open(struct inode * inode, struct file * filp)
 			ext4_journal_stop(handle);
 		}
 	}
-	if (ext4_encrypted_inode(inode)) {
-		ret = fscrypt_get_encryption_info(inode);
-		if (ret)
-			return -EACCES;
-		if (!fscrypt_has_encryption_key(inode))
-			return -ENOKEY;
-	}
 
-	dir = dget_parent(file_dentry(filp));
-	if (ext4_encrypted_inode(d_inode(dir)) &&
-			!fscrypt_has_permitted_context(d_inode(dir), inode)) {
-		ext4_warning(inode->i_sb,
-			     "Inconsistent encryption contexts: %lu/%lu",
-			     (unsigned long) d_inode(dir)->i_ino,
-			     (unsigned long) inode->i_ino);
-		dput(dir);
-		return -EPERM;
-	}
-	dput(dir);
+	ret = fscrypt_file_open(inode, filp);
+	if (ret)
+		return ret;
+
 	/*
 	 * Set up the jbd2_inode if we are opening the inode for
 	 * writing and the journal is present

@@ -3221,9 +3221,10 @@ static int ext4_link(struct dentry *old_dentry,
 
 	if (inode->i_nlink >= EXT4_LINK_MAX)
 		return -EMLINK;
-	if (ext4_encrypted_inode(dir) &&
-			!fscrypt_has_permitted_context(dir, inode))
-		return -EPERM;
+
+	err = fscrypt_prepare_link(old_dentry, dir, dentry);
+	if (err)
+		return err;
 
        if ((ext4_test_inode_flag(dir, EXT4_INODE_PROJINHERIT)) &&
 	   (!projid_eq(EXT4_I(dir)->i_projid,

@@ -3516,12 +3516,6 @@ static int ext4_rename(struct inode *old_dir, struct dentry *old_dentry,
 			EXT4_I(old_dentry->d_inode)->i_projid)))
 		return -EXDEV;
 
-	if ((ext4_encrypted_inode(old_dir) &&
-	     !fscrypt_has_encryption_key(old_dir)) ||
-	    (ext4_encrypted_inode(new_dir) &&
-	     !fscrypt_has_encryption_key(new_dir)))
-		return -ENOKEY;
-
 	retval = dquot_initialize(old.dir);
 	if (retval)
 		return retval;

@@ -3550,13 +3544,6 @@ static int ext4_rename(struct inode *old_dir, struct dentry *old_dentry,
 	if (!old.bh || le32_to_cpu(old.de->inode) != old.inode->i_ino)
 		goto end_rename;
 
-	if ((old.dir != new.dir) &&
-	    ext4_encrypted_inode(new.dir) &&
-	    !fscrypt_has_permitted_context(new.dir, old.inode)) {
-		retval = -EPERM;
-		goto end_rename;
-	}
-
 	new.bh = ext4_find_entry(new.dir, &new.dentry->d_name,
 				 &new.de, &new.inlined);
 	if (IS_ERR(new.bh)) {

@@ -3722,19 +3709,6 @@ static int ext4_cross_rename(struct inode *old_dir, struct dentry *old_dentry,
 	int retval;
 	struct timespec ctime;
 
-	if ((ext4_encrypted_inode(old_dir) &&
-	     !fscrypt_has_encryption_key(old_dir)) ||
-	    (ext4_encrypted_inode(new_dir) &&
-	     !fscrypt_has_encryption_key(new_dir)))
-		return -ENOKEY;
-
-	if ((ext4_encrypted_inode(old_dir) ||
-	     ext4_encrypted_inode(new_dir)) &&
-	    (old_dir != new_dir) &&
-	    (!fscrypt_has_permitted_context(new_dir, old.inode) ||
-	     !fscrypt_has_permitted_context(old_dir, new.inode)))
-		return -EPERM;
-
 	if ((ext4_test_inode_flag(new_dir, EXT4_INODE_PROJINHERIT) &&
 	     !projid_eq(EXT4_I(new_dir)->i_projid,
 			EXT4_I(old_dentry->d_inode)->i_projid)) ||

@@ -3861,12 +3835,19 @@ static int ext4_rename2(struct inode *old_dir, struct dentry *old_dentry,
 			struct inode *new_dir, struct dentry *new_dentry,
 			unsigned int flags)
 {
+	int err;
+
 	if (unlikely(ext4_forced_shutdown(EXT4_SB(old_dir->i_sb))))
 		return -EIO;
 
 	if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE | RENAME_WHITEOUT))
 		return -EINVAL;
 
+	err = fscrypt_prepare_rename(old_dir, old_dentry, new_dir, new_dentry,
+				     flags);
+	if (err)
+		return err;
+
 	if (flags & RENAME_EXCHANGE) {
 		return ext4_cross_rename(old_dir, old_dentry,
 					 new_dir, new_dentry);

@@ -1538,24 +1538,14 @@ static struct dentry *ext4_lookup(struct inode *dir, struct dentry *dentry, unsi
 	struct inode *inode;
 	struct ext4_dir_entry_2 *de;
 	struct buffer_head *bh;
+	int err;
 
-	if (ext4_encrypted_inode(dir)) {
-		int res = fscrypt_get_encryption_info(dir);
-
-		/*
-		 * DCACHE_ENCRYPTED_WITH_KEY is set if the dentry is
-		 * created while the directory was encrypted and we
-		 * have access to the key.
-		 */
-		if (fscrypt_has_encryption_key(dir))
-			fscrypt_set_encrypted_dentry(dentry);
-		fscrypt_set_d_op(dentry);
-		if (res && res != -ENOKEY)
-			return ERR_PTR(res);
-	}
+	err = fscrypt_prepare_lookup(dir, dentry, flags);
+	if (err)
+		return ERR_PTR(err);
 
-       if (dentry->d_name.len > EXT4_NAME_LEN)
-	       return ERR_PTR(-ENAMETOOLONG);
+	if (dentry->d_name.len > EXT4_NAME_LEN)
+		return ERR_PTR(-ENAMETOOLONG);
 
 	bh = ext4_find_entry(dir, &dentry->d_name, &de, NULL);
 	if (IS_ERR(bh))