On Thu, May 27, 2021 at 03:55:25PM -0700, Eric Biggers wrote:

From: Eric Biggers <redacted>

Typically, the cryptographic APIs that fscrypt uses take keys as byte
arrays, which avoids endianness issues.  However, siphash_key_t is an
exception.  It is defined as 'u64 key[2];', i.e. the 128-bit key is
expected to be given directly as two 64-bit words in CPU endianness.

fscrypt_derive_dirhash_key() forgot to take this into account.
Therefore, the SipHash keys used to index encrypted+casefolded
directories differ on big endian vs. little endian platforms.
This makes such directories non-portable between these platforms.

Fix this by always using the little endian order.  This is a breaking
change for big endian platforms, but this should be fine in practice
since the encrypt+casefold support isn't known to actually be used on
any big endian platforms yet.

Fixes: aa408f835d02 ("fscrypt: derive dirhash key for casefolded directories")
Cc: <redacted> # v5.6+
Signed-off-by: Eric Biggers <redacted>
---
 fs/crypto/keysetup.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

I missed that fscrypt_setup_iv_ino_lblk_32_key() has the same bug too.
I'll send out a new patch which fixes both of these...

- Eric