Commit 4ea9471f authored Jan 06, 2020 by Milan Broz Committed by Mike Snitzer Jan 14, 2020

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

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: ef43aa38 ("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>

parent bbb16584

drivers/md/dm-crypt.c

+8 −2

Original line number	Diff line number	Diff line
		@@ -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 */

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