[PATCH v3 11/11] fscrypt: factor helper for locking master key

From: Sweet Tea Dorminy <sweettea-kernel@dorminy.me>
To: Eric Biggers <ebiggers@kernel.org>,
	"Theodore Y. Ts'o" <tytso@mit.edu>,
	Jaegeuk Kim <jaegeuk@kernel.org>,
	linux-fscrypt@vger.kernel.org, kernel-team@meta.com
Cc: Sweet Tea Dorminy <sweettea-kernel@dorminy.me>
Subject: [PATCH v3 11/11] fscrypt: factor helper for locking master key
Date: Tue, 18 Apr 2023 13:04:48 -0400	[thread overview]
Message-ID: <0624b444f5a952f27b9de209f28ce3c3387e2f35.1681837335.git.sweettea-kernel@dorminy.me> (raw)
In-Reply-To: <cover.1681837335.git.sweettea-kernel@dorminy.me>

When keys are prepared at the point of use, using a pooled prepared key,
we'll need to lock and check the existence of the master key secret in
multiple places. So go on and factor out the helper.

Signed-off-by: Sweet Tea Dorminy <sweettea-kernel@dorminy.me>
---
 fs/crypto/keysetup.c | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/fs/crypto/keysetup.c b/fs/crypto/keysetup.c
index 55c416df6a71..9cd60e09b0c5 100644
--- a/fs/crypto/keysetup.c
+++ b/fs/crypto/keysetup.c
@@ -106,6 +106,17 @@ select_encryption_mode(const union fscrypt_policy *policy,
 	return ERR_PTR(-EINVAL);
 }
 
+static int lock_master_key(struct fscrypt_master_key *mk)
+{
+	down_read(&mk->mk_sem);
+
+	/* Has the secret been removed (via FS_IOC_REMOVE_ENCRYPTION_KEY)? */
+	if (!is_master_key_secret_present(&mk->mk_secret))
+		return -ENOKEY;
+
+	return 0;
+}
+
 /*
  * Prepare the crypto transform object or blk-crypto key in @prep_key, given the
  * raw key, encryption mode (@ci->ci_mode), flag indicating which encryption
@@ -569,13 +580,10 @@ static int find_and_lock_master_key(const struct fscrypt_info *ci,
 		*mk_ret = NULL;
 		return 0;
 	}
-	down_read(&mk->mk_sem);
 
-	/* Has the secret been removed (via FS_IOC_REMOVE_ENCRYPTION_KEY)? */
-	if (!is_master_key_secret_present(&mk->mk_secret)) {
-		err = -ENOKEY;
+	err = lock_master_key(mk);
+	if (err)
 		goto out_release_key;
-	}
 
 	if (!fscrypt_valid_master_key_size(mk, ci)) {
 		err = -ENOKEY;
-- 
2.40.0

