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From: Eric Biggers <ebiggers@kernel.org>
To: linux-fscrypt@vger.kernel.org
Cc: linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org,
	linux-f2fs-devel@lists.sourceforge.net,
	linux-mtd@lists.infradead.org, linux-unionfs@vger.kernel.org,
	Sarthak Kukreti <sarthakkukreti@chromium.org>,
	Gao Xiang <gaoxiang25@huawei.com>
Subject: [PATCH v2 4/5] fscrypt: only set dentry_operations on ciphertext dentries
Date: Wed, 20 Mar 2019 11:39:12 -0700	[thread overview]
Message-ID: <20190320183913.12686-5-ebiggers@kernel.org> (raw)
In-Reply-To: <20190320183913.12686-1-ebiggers@kernel.org>

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 overlayfs 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 --git a/fs/crypto/hooks.c b/fs/crypto/hooks.c
index 2e7498a821a48..9d8910e86ee5d 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);
-- 
2.21.0.225.g810b269d1ac-goog


  parent reply	other threads:[~2019-03-20 18:40 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-03-20 18:39 [PATCH v2 0/5] fscrypt: d_revalidate fixes and cleanups Eric Biggers
2019-03-20 18:39 ` [PATCH v2 1/5] fscrypt: clean up and improve dentry revalidation Eric Biggers
2019-04-16 23:08   ` Theodore Ts'o
2019-04-17  0:10     ` Eric Biggers
2019-04-17 13:50       ` Theodore Ts'o
2019-03-20 18:39 ` [PATCH v2 2/5] fscrypt: fix race allowing rename() and link() of ciphertext dentries Eric Biggers
2019-04-17 13:53   ` Theodore Ts'o
2019-03-20 18:39 ` [PATCH v2 3/5] fs, fscrypt: clear DCACHE_ENCRYPTED_NAME when unaliasing directory Eric Biggers
2019-04-17 14:06   ` Theodore Ts'o
2019-03-20 18:39 ` Eric Biggers [this message]
2019-04-17 14:07   ` [PATCH v2 4/5] fscrypt: only set dentry_operations on ciphertext dentries Theodore Ts'o
2019-03-20 18:39 ` [PATCH v2 5/5] fscrypt: fix race where ->lookup() marks plaintext dentry as ciphertext Eric Biggers
2019-04-17 14:24   ` Theodore Ts'o
2019-04-01 17:11 ` [PATCH v2 0/5] fscrypt: d_revalidate fixes and cleanups Eric Biggers
2019-04-08  8:22   ` Richard Weinberger

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