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

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