fscrypt updates for 6.3

Simplify the implementation of the test_dummy_encryption mount option by
 adding the "test dummy key" on-demand.
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Merge tag 'fscrypt-for-linus' of git://git.kernel.org/pub/scm/fs/fscrypt/linux

Pull fscrypt updates from Eric Biggers:
 "Simplify the implementation of the test_dummy_encryption mount option
  by adding the 'test dummy key' on-demand"

* tag 'fscrypt-for-linus' of git://git.kernel.org/pub/scm/fs/fscrypt/linux:
  fscrypt: clean up fscrypt_add_test_dummy_key()
  fs/super.c: stop calling fscrypt_destroy_keyring() from __put_super()
  f2fs: stop calling fscrypt_add_test_dummy_key()
  ext4: stop calling fscrypt_add_test_dummy_key()
  fscrypt: add the test dummy encryption key on-demand

fs/crypto/fscrypt_private.h

@@ -573,6 +573,9 @@ fscrypt_find_master_key(struct super_block *sb,
 int fscrypt_get_test_dummy_key_identifier(
 			  u8 key_identifier[FSCRYPT_KEY_IDENTIFIER_SIZE]);
 
+int fscrypt_add_test_dummy_key(struct super_block *sb,
+			       struct fscrypt_key_specifier *key_spec);
+
 int fscrypt_verify_key_added(struct super_block *sb,
 			     const u8 identifier[FSCRYPT_KEY_IDENTIFIER_SIZE]);
 
@@ -651,6 +654,7 @@ bool fscrypt_policies_equal(const union fscrypt_policy *policy1,
 			    const union fscrypt_policy *policy2);
 int fscrypt_policy_to_key_spec(const union fscrypt_policy *policy,
 			       struct fscrypt_key_specifier *key_spec);
+const union fscrypt_policy *fscrypt_get_dummy_policy(struct super_block *sb);
 bool fscrypt_supported_policy(const union fscrypt_policy *policy_u,
 			      const struct inode *inode);
 int fscrypt_policy_from_context(union fscrypt_policy *policy_u,

fs/crypto/keyring.c

@@ -211,10 +211,6 @@ static int allocate_filesystem_keyring(struct super_block *sb)
  * are still available at this time; this is important because after user file
  * accesses have been allowed, this function may need to evict keys from the
  * keyslots of an inline crypto engine, which requires the block device(s).
- *
- * This is also called when the super_block is being freed.  This is needed to
- * avoid a memory leak if mounting fails after the "test_dummy_encryption"
- * option was processed, as in that case the unmount-time call isn't made.
  */
 void fscrypt_destroy_keyring(struct super_block *sb)
 {
@@ -778,34 +774,26 @@ out:
 /**
  * fscrypt_add_test_dummy_key() - add the test dummy encryption key
  * @sb: the filesystem instance to add the key to
- * @dummy_policy: the encryption policy for test_dummy_encryption
+ * @key_spec: the key specifier of the test dummy encryption key
  *
- * If needed, add the key for the test_dummy_encryption mount option to the
+ * Add the key for the test_dummy_encryption mount option to the filesystem.  To
- * filesystem.  To prevent misuse of this mount option, a per-boot random key is
+ * prevent misuse of this mount option, a per-boot random key is used instead of
- * used instead of a hardcoded one.  This makes it so that any encrypted files
+ * a hardcoded one.  This makes it so that any encrypted files created using
- * created using this option won't be accessible after a reboot.
+ * this option won't be accessible after a reboot.
  *
  * Return: 0 on success, -errno on failure
  */
 int fscrypt_add_test_dummy_key(struct super_block *sb,
-			       const struct fscrypt_dummy_policy *dummy_policy)
+			       struct fscrypt_key_specifier *key_spec)
 {
-	const union fscrypt_policy *policy = dummy_policy->policy;
-	struct fscrypt_key_specifier key_spec;
 	struct fscrypt_master_key_secret secret;
 	int err;
 
-	if (!policy)
-		return 0;
-	err = fscrypt_policy_to_key_spec(policy, &key_spec);
-	if (err)
-		return err;
 	fscrypt_get_test_dummy_secret(&secret);
-	err = add_master_key(sb, &secret, &key_spec);
+	err = add_master_key(sb, &secret, key_spec);
 	wipe_master_key_secret(&secret);
 	return err;
 }
-EXPORT_SYMBOL_GPL(fscrypt_add_test_dummy_key);
 
 /*
  * Verify that the current user has added a master key with the given identifier

fs/crypto/keysetup.c

@@ -438,6 +438,7 @@ static int setup_file_encryption_key(struct fscrypt_info *ci,
 				     bool need_dirhash_key,
 				     struct fscrypt_master_key **mk_ret)
 {
+	struct super_block *sb = ci->ci_inode->i_sb;
 	struct fscrypt_key_specifier mk_spec;
 	struct fscrypt_master_key *mk;
 	int err;
@@ -450,8 +451,26 @@ static int setup_file_encryption_key(struct fscrypt_info *ci,
 	if (err)
 		return err;
 
-	mk = fscrypt_find_master_key(ci->ci_inode->i_sb, &mk_spec);
+	mk = fscrypt_find_master_key(sb, &mk_spec);
-	if (!mk) {
+	if (unlikely(!mk)) {
+		const union fscrypt_policy *dummy_policy =
+			fscrypt_get_dummy_policy(sb);
+
+		/*
+		 * Add the test_dummy_encryption key on-demand.  In principle,
+		 * it should be added at mount time.  Do it here instead so that
+		 * the individual filesystems don't need to worry about adding
+		 * this key at mount time and cleaning up on mount failure.
+		 */
+		if (dummy_policy &&
+		    fscrypt_policies_equal(dummy_policy, &ci->ci_policy)) {
+			err = fscrypt_add_test_dummy_key(sb, &mk_spec);
+			if (err)
+				return err;
+			mk = fscrypt_find_master_key(sb, &mk_spec);
+		}
+	}
+	if (unlikely(!mk)) {
 		if (ci->ci_policy.version != FSCRYPT_POLICY_V1)
 			return -ENOKEY;
 

fs/crypto/policy.c

@@ -53,8 +53,7 @@ int fscrypt_policy_to_key_spec(const union fscrypt_policy *policy,
 	}
 }
 
-static const union fscrypt_policy *
+const union fscrypt_policy *fscrypt_get_dummy_policy(struct super_block *sb)
-fscrypt_get_dummy_policy(struct super_block *sb)
 {
 	if (!sb->s_cop->get_dummy_policy)
 		return NULL;

fs/ext4/super.c

@@ -2635,7 +2635,6 @@ static int ext4_check_test_dummy_encryption(const struct fs_context *fc,
 {
 	const struct ext4_fs_context *ctx = fc->fs_private;
 	const struct ext4_sb_info *sbi = EXT4_SB(sb);
-	int err;
 
 	if (!fscrypt_is_dummy_policy_set(&ctx->dummy_enc_policy))
 		return 0;
@@ -2668,17 +2667,7 @@ static int ext4_check_test_dummy_encryption(const struct fs_context *fc,
 			 "Conflicting test_dummy_encryption options");
 		return -EINVAL;
 	}
-	/*
+	return 0;
-	 * fscrypt_add_test_dummy_key() technically changes the super_block, so
-	 * technically it should be delayed until ext4_apply_options() like the
-	 * other changes.  But since we never get here for remounts (see above),
-	 * and this is the last chance to report errors, we do it here.
-	 */
-	err = fscrypt_add_test_dummy_key(sb, &ctx->dummy_enc_policy);
-	if (err)
-		ext4_msg(NULL, KERN_WARNING,
-			 "Error adding test dummy encryption key [%d]", err);
-	return err;
 }
 
 static void ext4_apply_test_dummy_encryption(struct ext4_fs_context *ctx,

fs/f2fs/super.c

@@ -540,12 +540,6 @@ static int f2fs_set_test_dummy_encryption(struct super_block *sb,
 				  opt, err);
 		return -EINVAL;
 	}
-	err = fscrypt_add_test_dummy_key(sb, policy);
-	if (err) {
-		f2fs_warn(sbi, "Error adding test dummy encryption key [%d]",
-			  err);
-		return err;
-	}
 	f2fs_warn(sbi, "Test dummy encryption mode enabled");
 	return 0;
 }

fs/super.c

@@ -291,7 +291,6 @@ static void __put_super(struct super_block *s)
 		WARN_ON(s->s_inode_lru.node);
 		WARN_ON(!list_empty(&s->s_mounts));
 		security_sb_free(s);
-		fscrypt_destroy_keyring(s);
 		put_user_ns(s->s_user_ns);
 		kfree(s->s_subtype);
 		call_rcu(&s->rcu, destroy_super_rcu);

include/linux/fscrypt.h

@@ -309,8 +309,6 @@ fscrypt_free_dummy_policy(struct fscrypt_dummy_policy *dummy_policy)
 /* keyring.c */
 void fscrypt_destroy_keyring(struct super_block *sb);
 int fscrypt_ioctl_add_key(struct file *filp, void __user *arg);
-int fscrypt_add_test_dummy_key(struct super_block *sb,
-			       const struct fscrypt_dummy_policy *dummy_policy);
 int fscrypt_ioctl_remove_key(struct file *filp, void __user *arg);
 int fscrypt_ioctl_remove_key_all_users(struct file *filp, void __user *arg);
 int fscrypt_ioctl_get_key_status(struct file *filp, void __user *arg);
@@ -530,13 +528,6 @@ static inline int fscrypt_ioctl_add_key(struct file *filp, void __user *arg)
 	return -EOPNOTSUPP;
 }
 
-static inline int
-fscrypt_add_test_dummy_key(struct super_block *sb,
-			   const struct fscrypt_dummy_policy *dummy_policy)
-{
-	return 0;
-}
-
 static inline int fscrypt_ioctl_remove_key(struct file *filp, void __user *arg)
 {
 	return -EOPNOTSUPP;