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Diffstat (limited to 'Documentation/filesystems/fscrypt.rst')
| -rw-r--r-- | Documentation/filesystems/fscrypt.rst | 16 |
1 files changed, 12 insertions, 4 deletions
diff --git a/Documentation/filesystems/fscrypt.rst b/Documentation/filesystems/fscrypt.rst index 3a7b60521b94..08c23b60e016 100644 --- a/Documentation/filesystems/fscrypt.rst +++ b/Documentation/filesystems/fscrypt.rst @@ -343,9 +343,9 @@ FS_IOC_SET_ENCRYPTION_POLICY can fail with the following errors: - ``ENOTEMPTY``: the file is unencrypted and is a nonempty directory - ``ENOTTY``: this type of filesystem does not implement encryption - ``EOPNOTSUPP``: the kernel was not configured with encryption - support for this filesystem, or the filesystem superblock has not + support for filesystems, or the filesystem superblock has not had encryption enabled on it. (For example, to use encryption on an - ext4 filesystem, CONFIG_EXT4_ENCRYPTION must be enabled in the + ext4 filesystem, CONFIG_FS_ENCRYPTION must be enabled in the kernel config, and the superblock must have had the "encrypt" feature flag enabled using ``tune2fs -O encrypt`` or ``mkfs.ext4 -O encrypt``.) @@ -451,10 +451,18 @@ astute users may notice some differences in behavior: - Unencrypted files, or files encrypted with a different encryption policy (i.e. different key, modes, or flags), cannot be renamed or linked into an encrypted directory; see `Encryption policy - enforcement`_. Attempts to do so will fail with EPERM. However, + enforcement`_. Attempts to do so will fail with EXDEV. However, encrypted files can be renamed within an encrypted directory, or into an unencrypted directory. + Note: "moving" an unencrypted file into an encrypted directory, e.g. + with the `mv` program, is implemented in userspace by a copy + followed by a delete. Be aware that the original unencrypted data + may remain recoverable from free space on the disk; prefer to keep + all files encrypted from the very beginning. The `shred` program + may be used to overwrite the source files but isn't guaranteed to be + effective on all filesystems and storage devices. + - Direct I/O is not supported on encrypted files. Attempts to use direct I/O on such files will fall back to buffered I/O. @@ -541,7 +549,7 @@ not be encrypted. Except for those special files, it is forbidden to have unencrypted files, or files encrypted with a different encryption policy, in an encrypted directory tree. Attempts to link or rename such a file into -an encrypted directory will fail with EPERM. This is also enforced +an encrypted directory will fail with EXDEV. This is also enforced during ->lookup() to provide limited protection against offline attacks that try to disable or downgrade encryption in known locations where applications may later write sensitive data. It is recommended |