diff mbox series

[4/5] fscrypt: only set dentry_operations on ciphertext dentries

Message ID 20190317200444.5967-5-ebiggers@kernel.org (mailing list archive)
State Superseded
Headers show
Series fscrypt: d_revalidate fixes and cleanups | expand

Commit Message

Eric Biggers March 17, 2019, 8:04 p.m. UTC 
From: Eric Biggers <ebiggers@google.com>

Plaintext dentries are always valid, so only set fscrypt_d_ops on
ciphertext dentries.

Besides marginally improved performance, this allows overlayfs to use an
fscrypt-encrypted upperdir, provided that all the following are true:

    (1) The fscrypt encryption key is placed in the keyring before
	mounting overlayfs, and remains while the overlayfs is mounted.

    (2) The workdir uses the same encryption policy.

    (3) No dentries for the ciphertext names of subdirectories have been
	created in the upperdir or workdir yet.  (Since otherwise
	d_splice_alias() will reuse the old dentry with ->d_op set.)

One potential use case is using an ephemeral encryption key to encrypt
all files created or changed by a container, so that they can be
securely erased ("crypto-shredded") after the container stops.

Signed-off-by: Eric Biggers <ebiggers@google.com>
---
 fs/crypto/hooks.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)
diff mbox series

Patch

diff --git a/fs/crypto/hooks.c b/fs/crypto/hooks.c
index 2e7498a821a4..9d8910e86ee5 100644
--- a/fs/crypto/hooks.c
+++ b/fs/crypto/hooks.c
@@ -115,9 +115,8 @@  int __fscrypt_prepare_lookup(struct inode *dir, struct dentry *dentry)
 		spin_lock(&dentry->d_lock);
 		dentry->d_flags |= DCACHE_ENCRYPTED_NAME;
 		spin_unlock(&dentry->d_lock);
+		d_set_d_op(dentry, &fscrypt_d_ops);
 	}
-
-	d_set_d_op(dentry, &fscrypt_d_ops);
 	return 0;
 }
 EXPORT_SYMBOL_GPL(__fscrypt_prepare_lookup);