If benbi IV is used in AEAD constructionm for example cryptsetup luksFormat <device> --cipher twofish-xts-benbi --key-size 512 --integrity=hmac-sha256 the constructor ues wrong skcipher function and crashes.

BUG: kernel NULL pointer dereference, address: 00000014 ... EIP: crypt_iv_benbi_ctr+0x15/0x70 [dm_crypt] Call Trace: ? crypt_subkey_size+0x20/0x20 [dm_crypt] crypt_ctr+0x567/0xfc0 [dm_crypt] dm_table_add_target+0x15f/0x340 [dm_mod]

This patch fixes the problem with properly using crypt_aead_blocksize() in this case.

Reported in https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=941051

Signed-off-by: Milan Broz gmazyland@gmail.com Cc: stable@vger.kernel.org # v4.12+ --- drivers/md/dm-crypt.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c index f9370a1a574b..fd30143dca91 100644 --- a/drivers/md/dm-crypt.c +++ b/drivers/md/dm-crypt.c @@ -343,8 +343,14 @@ static int crypt_iv_essiv_gen(struct crypt_config *cc, u8 *iv, static int crypt_iv_benbi_ctr(struct crypt_config *cc, struct dm_target *ti, const char *opts) { - unsigned bs = crypto_skcipher_blocksize(any_tfm(cc)); - int log = ilog2(bs); + unsigned bs; + int log; + + if (test_bit(CRYPT_MODE_INTEGRITY_AEAD, &cc->cipher_flags)) + bs = crypto_aead_blocksize(any_tfm_aead(cc)); + else + bs = crypto_skcipher_blocksize(any_tfm(cc)); + log = ilog2(bs);

/* we need to calculate how far we must shift the sector count * to get the cipher block count, we use this shift in _gen */