[PATCH 5.5 144/367] dm crypt: fix benbi IV constructor crash if used in authenticated mode

Greg Kroah-Hartman
2020-02-10T13:03:38Z

From: Milan Broz <gmazyland@gmail.com>

commit 4ea9471fbd1addb25a4d269991dc724e200ca5b5 upstream.

If benbi IV is used in AEAD construction, for example:
cryptsetup luksFormat <device> --cipher twofish-xts-benbi --key-size 512 --integrity=hmac-sha256
the constructor uses 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]

Fix this by properly using crypt_aead_blocksize() in this case.

Fixes: ef43aa38063a6 ("dm crypt: add cryptographic data integrity protection (authenticated encryption)")
Cc: stable@vger.kernel.org # v4.12+
Link: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=941051
Reported-by: Jerad Simpson <jbsimpson@gmail.com>
Signed-off-by: Milan Broz <gmazyland@gmail.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/md/dm-crypt.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)

--- a/drivers/md/dm-crypt.c
+++ b/drivers/md/dm-crypt.c
@@ -331,8 +331,14 @@ static int crypt_iv_essiv_gen(struct cry
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 */