fscrypt: add new helper functions for test_dummy_encryption

Unfortunately the design of fscrypt_set_test_dummy_encryption() doesn't
work properly for the new mount API, as it combines too many steps into
one function:

  - Parse the argument to test_dummy_encryption
  - Check the setting against the filesystem instance
  - Apply the setting to the filesystem instance

The new mount API has split these into separate steps.  ext4 partially
worked around this by duplicating some of the logic, but it still had
some bugs.  To address this, add some new helper functions that split up
the steps of fscrypt_set_test_dummy_encryption():

  - fscrypt_parse_test_dummy_encryption()
  - fscrypt_dummy_policies_equal()
  - fscrypt_add_test_dummy_key()

While we're add it, also add a function fscrypt_is_dummy_policy_set()
which will be useful to avoid some #ifdef's.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Link: https://lore.kernel.org/r/20220501050857.538984-5-ebiggers@kernel.org

1 files changed, 39 insertions, 0 deletions

diff --git a/include/linux/fscrypt.h b/include/linux/fscrypt.h
index efc7f96e5e26..e60d57c99cb6 100644
--- a/include/linux/fscrypt.h
+++ b/include/linux/fscrypt.h
@@ -32,6 +32,7 @@
 
 union fscrypt_policy;
 struct fscrypt_info;
+struct fs_parameter;
 struct seq_file;
 
 struct fscrypt_str {
@@ -289,10 +290,19 @@ struct fscrypt_dummy_policy {
 	const union fscrypt_policy *policy;
 };
 
+int fscrypt_parse_test_dummy_encryption(const struct fs_parameter *param,
+				    struct fscrypt_dummy_policy *dummy_policy);
+bool fscrypt_dummy_policies_equal(const struct fscrypt_dummy_policy *p1,
+				  const struct fscrypt_dummy_policy *p2);
 int fscrypt_set_test_dummy_encryption(struct super_block *sb, const char *arg,
 				struct fscrypt_dummy_policy *dummy_policy);
 void fscrypt_show_test_dummy_encryption(struct seq_file *seq, char sep,
 					struct super_block *sb);
+static inline bool
+fscrypt_is_dummy_policy_set(const struct fscrypt_dummy_policy *dummy_policy)
+{
+	return dummy_policy->policy != NULL;
+}
 static inline void
 fscrypt_free_dummy_policy(struct fscrypt_dummy_policy *dummy_policy)
 {
@@ -303,6 +313,8 @@ fscrypt_free_dummy_policy(struct fscrypt_dummy_policy *dummy_policy)
 /* keyring.c */
 void fscrypt_sb_free(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);
@@ -477,12 +489,32 @@ static inline int fscrypt_set_context(struct inode *inode, void *fs_data)
 struct fscrypt_dummy_policy {
 };
 
+static inline int
+fscrypt_parse_test_dummy_encryption(const struct fs_parameter *param,
+				    struct fscrypt_dummy_policy *dummy_policy)
+{
+	return -EINVAL;
+}
+
+static inline bool
+fscrypt_dummy_policies_equal(const struct fscrypt_dummy_policy *p1,
+			     const struct fscrypt_dummy_policy *p2)
+{
+	return true;
+}
+
 static inline void fscrypt_show_test_dummy_encryption(struct seq_file *seq,
 						      char sep,
 						      struct super_block *sb)
 {
 }
 
+static inline bool
+fscrypt_is_dummy_policy_set(const struct fscrypt_dummy_policy *dummy_policy)
+{
+	return false;
+}
+
 static inline void
 fscrypt_free_dummy_policy(struct fscrypt_dummy_policy *dummy_policy)
 {
@@ -498,6 +530,13 @@ 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;