fscrypt: document symlink length restriction (2f46a2bc) · Commits · 戴 / test

Documentation/filesystems/fscrypt.rst

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		@@ -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.