dm crypt: fix benbi IV constructor crash if used in authenticated mode

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>

diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c
index 9a183882ee4beeeef5915f1c34c9249edd2b3d87..492bbe0584d909436870ab0274b0b668cf577bd0 100644 (file)
--- a/drivers/md/dm-crypt.c
+++ b/drivers/md/dm-crypt.c
@@ -331,8 +331,14 @@ 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 */