[PATCH v6 2/8] fscrypt: split and rename setup_file_encryption_key()

[Sweet Tea Dorminy <sweettea-kernel@xxxxxxxxxx>]

At present, setup_file_encryption_key() does several things: it finds
and locks the master key, and then calls into the appropriate functions
to setup the prepared key for the fscrypt_info. The code is clearer to
follow if these functions are divided.

Thus, move calling the appropriate file key setup function into a new
fscrypt_setup_file_key() function. After the file key setup functions
are moved, the remaining function can take a const fscrypt_info, and is
renamed find_and_lock_master_key() to precisely describe its action.

Signed-off-by: Sweet Tea Dorminy <sweettea-kernel@xxxxxxxxxx>
---
 fs/crypto/keysetup.c | 77 ++++++++++++++++++++++++++++++--------------
 1 file changed, 52 insertions(+), 25 deletions(-)

diff --git a/fs/crypto/keysetup.c b/fs/crypto/keysetup.c
index b89c32ad19fb..727d473b6b03 100644
--- a/fs/crypto/keysetup.c
+++ b/fs/crypto/keysetup.c
@@ -386,6 +386,43 @@ static int fscrypt_setup_v2_file_key(struct fscrypt_info *ci,
 	return 0;
 }
 
+/*
+ * Find or create the appropriate prepared key for an info.
+ */
+static int fscrypt_setup_file_key(struct fscrypt_info *ci,
+				  struct fscrypt_master_key *mk,
+				  bool need_dirhash_key)
+{
+	int err;
+
+	if (!mk) {
+		if (ci->ci_policy.version != FSCRYPT_POLICY_V1)
+			return -ENOKEY;
+
+		/*
+		 * As a legacy fallback for v1 policies, search for the key in
+		 * the current task's subscribed keyrings too.  Don't move this
+		 * to before the search of ->s_master_keys, since users
+		 * shouldn't be able to override filesystem-level keys.
+		 */
+		return fscrypt_setup_v1_file_key_via_subscribed_keyrings(ci);
+	}
+
+	switch (ci->ci_policy.version) {
+	case FSCRYPT_POLICY_V1:
+		err = fscrypt_setup_v1_file_key(ci, mk->mk_secret.raw);
+		break;
+	case FSCRYPT_POLICY_V2:
+		err = fscrypt_setup_v2_file_key(ci, mk, need_dirhash_key);
+		break;
+	default:
+		WARN_ON_ONCE(1);
+		err = -EINVAL;
+		break;
+	}
+	return err;
+}
+
 /*
  * Check whether the size of the given master key (@mk) is appropriate for the
  * encryption settings which a particular file will use (@ci).
@@ -426,7 +463,7 @@ static bool fscrypt_valid_master_key_size(const struct fscrypt_master_key *mk,
 }
 
 /*
- * Find the master key, then set up the inode's actual encryption key.
+ * Find and lock the master key.
  *
  * If the master key is found in the filesystem-level keyring, then it is
  * returned in *mk_ret with its semaphore read-locked.  This is needed to ensure
@@ -434,9 +471,8 @@ static bool fscrypt_valid_master_key_size(const struct fscrypt_master_key *mk,
  * multiple tasks may race to create an fscrypt_info for the same inode), and to
  * synchronize the master key being removed with a new inode starting to use it.
  */
-static int setup_file_encryption_key(struct fscrypt_info *ci,
-				     bool need_dirhash_key,
-				     struct fscrypt_master_key **mk_ret)
+static int find_and_lock_master_key(const struct fscrypt_info *ci,
+				    struct fscrypt_master_key **mk_ret)
 {
 	struct super_block *sb = ci->ci_inode->i_sb;
 	struct fscrypt_key_specifier mk_spec;
@@ -466,17 +502,19 @@ static int setup_file_encryption_key(struct fscrypt_info *ci,
 			mk = fscrypt_find_master_key(sb, &mk_spec);
 		}
 	}
+
 	if (unlikely(!mk)) {
 		if (ci->ci_policy.version != FSCRYPT_POLICY_V1)
 			return -ENOKEY;
 
 		/*
-		 * As a legacy fallback for v1 policies, search for the key in
-		 * the current task's subscribed keyrings too.  Don't move this
-		 * to before the search of ->s_master_keys, since users
-		 * shouldn't be able to override filesystem-level keys.
+		 * This might be the case of a v1 policy using a process
+		 * subscribed keyring to get the key, so there may not be
+		 * a relevant master key.
 		 */
-		return fscrypt_setup_v1_file_key_via_subscribed_keyrings(ci);
+
+		*mk_ret = NULL;
+		return 0;
 	}
 	down_read(&mk->mk_sem);
 
@@ -491,21 +529,6 @@ static int setup_file_encryption_key(struct fscrypt_info *ci,
 		goto out_release_key;
 	}
 
-	switch (ci->ci_policy.version) {
-	case FSCRYPT_POLICY_V1:
-		err = fscrypt_setup_v1_file_key(ci, mk->mk_secret.raw);
-		break;
-	case FSCRYPT_POLICY_V2:
-		err = fscrypt_setup_v2_file_key(ci, mk, need_dirhash_key);
-		break;
-	default:
-		WARN_ON_ONCE(1);
-		err = -EINVAL;
-		break;
-	}
-	if (err)
-		goto out_release_key;
-
 	*mk_ret = mk;
 	return 0;
 
@@ -580,7 +603,11 @@ fscrypt_setup_encryption_info(struct inode *inode,
 	if (res)
 		goto out;
 
-	res = setup_file_encryption_key(crypt_info, need_dirhash_key, &mk);
+	res = find_and_lock_master_key(crypt_info, &mk);
+	if (res)
+		goto out;
+
+	res = fscrypt_setup_file_key(crypt_info, mk, need_dirhash_key);
 	if (res)
 		goto out;
 
-- 
2.41.0