dm crypt: don't overallocate the integrity tag space

bio_sectors() returns the value in the units of 512-byte sectors (no
matter what the real sector size of the device).  dm-crypt multiplies
bio_sectors() by on_disk_tag_size to calculate the space allocated for
integrity tags.  If dm-crypt is running with sector size larger than
512b, it allocates more data than is needed.

Device Mapper trims the extra space when passing the bio to
dm-integrity, so this bug didn't result in any visible misbehavior.
But it must be fixed to avoid wasteful memory allocation for the block
integrity payload.

Fixes: ef43aa38063a6 ("dm crypt: add cryptographic data integrity protection (authenticated encryption)")
Cc: stable@vger.kernel.org # 4.12+
Reported-by: Milan Broz <mbroz@redhat.com>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c
index 47d4e0d30bf08b3c5179c9196100b129f8b0437c..dd538e6b27480c5583731cab60738adb4064f1c0 100644 (file)
--- a/drivers/md/dm-crypt.c
+++ b/drivers/md/dm-crypt.c
@@ -932,7 +932,7 @@ static int dm_crypt_integrity_io_alloc(struct dm_crypt_io *io, struct bio *bio)
        if (IS_ERR(bip))
                return PTR_ERR(bip);
 
-       tag_len = io->cc->on_disk_tag_size * bio_sectors(bio);
+       tag_len = io->cc->on_disk_tag_size * (bio_sectors(bio) >> io->cc->sector_shift);
 
        bip->bip_iter.bi_size = tag_len;
        bip->bip_iter.bi_sector = io->cc->start + io->sector;