fscrypt: only set dentry_operations on ciphertext dentries
commit d456a33f04
upstream.
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>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
committed by
Greg Kroah-Hartman
parent
906242d10b
commit
f217c9685c
@ -115,9 +115,8 @@ int __fscrypt_prepare_lookup(struct inode *dir, struct dentry *dentry)
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spin_lock(&dentry->d_lock);
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spin_lock(&dentry->d_lock);
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dentry->d_flags |= DCACHE_ENCRYPTED_NAME;
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dentry->d_flags |= DCACHE_ENCRYPTED_NAME;
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spin_unlock(&dentry->d_lock);
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spin_unlock(&dentry->d_lock);
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d_set_d_op(dentry, &fscrypt_d_ops);
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}
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}
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d_set_d_op(dentry, &fscrypt_d_ops);
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return 0;
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return 0;
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}
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}
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EXPORT_SYMBOL_GPL(__fscrypt_prepare_lookup);
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EXPORT_SYMBOL_GPL(__fscrypt_prepare_lookup);
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