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| author | Eric Biggers <ebiggers@google.com> | 2018-01-11 23:30:09 -0500 |
|---|---|---|
| committer | Theodore Ts'o <tytso@mit.edu> | 2018-01-11 23:30:09 -0500 |
| commit | 2f46a2bc2694877332f9c1ff47acb7fa117e168a (patch) | |
| tree | 4770143c03bd8b19c0b5b7205ef35f0af4e9cc0e | |
| parent | b9db0b4a68d373897119d1e0a3beebe1c1a23936 (diff) | |
| download | linux-2f46a2bc2694877332f9c1ff47acb7fa117e168a.tar.bz2 | |
fscrypt: document symlink length restriction
Document that encryption reduces the maximum length of a symlink target
slightly.
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
| -rw-r--r-- | Documentation/filesystems/fscrypt.rst | 10 |
1 files changed, 8 insertions, 2 deletions
diff --git a/Documentation/filesystems/fscrypt.rst b/Documentation/filesystems/fscrypt.rst index 776ddc655f79..cfbc18f0d9c9 100644 --- a/Documentation/filesystems/fscrypt.rst +++ b/Documentation/filesystems/fscrypt.rst @@ -448,8 +448,14 @@ astute users may notice some differences in behavior: - The st_size of an encrypted symlink will not necessarily give the length of the symlink target as required by POSIX. It will actually - give the length of the ciphertext, which may be slightly longer than - the plaintext due to the NUL-padding. + give the length of the ciphertext, which will be slightly longer + than the plaintext due to NUL-padding and an extra 2-byte overhead. + +- The maximum length of an encrypted symlink is 2 bytes shorter than + the maximum length of an unencrypted symlink. For example, on an + EXT4 filesystem with a 4K block size, unencrypted symlinks can be up + to 4095 bytes long, while encrypted symlinks can only be up to 4093 + bytes long (both lengths excluding the terminating null). Note that mmap *is* supported. This is possible because the pagecache for an encrypted file contains the plaintext, not the ciphertext. |