From: Eric Biggers <ebiggers@kernel.org>
To: Satya Tangirala <satyat@google.com>
Cc: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org,
dm-devel@redhat.com, Jens Axboe <axboe@kernel.dk>,
Alasdair Kergon <agk@redhat.com>,
Mike Snitzer <snitzer@redhat.com>
Subject: Re: [PATCH 3/3] dm: enable may_passthrough_inline_crypto on some targets
Date: Mon, 21 Sep 2020 17:49:10 -0700 [thread overview]
Message-ID: <20200922004910.GD32959@sol.localdomain> (raw)
In-Reply-To: <20200909234422.76194-4-satyat@google.com>
On Wed, Sep 09, 2020 at 11:44:22PM +0000, Satya Tangirala wrote:
> From: Eric Biggers <ebiggers@google.com>
>
> dm-linear and dm-flakey obviously can pass through inline crypto support.
>
> dm-zero should declare that it passes through inline crypto support, since
> any reads from dm-zero should return zeroes, and blk-crypto should not
> attempt to decrypt data returned from dm-zero.
>
> Signed-off-by: Eric Biggers <ebiggers@google.com>
> Co-developed-by: Satya Tangirala <satyat@google.com>
> Signed-off-by: Satya Tangirala <satyat@google.com>
> ---
> drivers/md/dm-flakey.c | 1 +
> drivers/md/dm-linear.c | 1 +
> drivers/md/dm-zero.c | 1 +
> 3 files changed, 3 insertions(+)
>
> diff --git a/drivers/md/dm-flakey.c b/drivers/md/dm-flakey.c
> index a2cc9e45cbba..655286dacc35 100644
> --- a/drivers/md/dm-flakey.c
> +++ b/drivers/md/dm-flakey.c
> @@ -253,6 +253,7 @@ static int flakey_ctr(struct dm_target *ti, unsigned int argc, char **argv)
> ti->num_discard_bios = 1;
> ti->per_io_data_size = sizeof(struct per_bio_data);
> ti->private = fc;
> + ti->may_passthrough_inline_crypto = true;
> return 0;
>
> bad:
> diff --git a/drivers/md/dm-linear.c b/drivers/md/dm-linear.c
> index e1db43446327..6d81878e2ca8 100644
> --- a/drivers/md/dm-linear.c
> +++ b/drivers/md/dm-linear.c
> @@ -62,6 +62,7 @@ static int linear_ctr(struct dm_target *ti, unsigned int argc, char **argv)
> ti->num_secure_erase_bios = 1;
> ti->num_write_same_bios = 1;
> ti->num_write_zeroes_bios = 1;
> + ti->may_passthrough_inline_crypto = true;
> ti->private = lc;
> return 0;
>
> diff --git a/drivers/md/dm-zero.c b/drivers/md/dm-zero.c
> index b65ca8dcfbdc..07e02f3a9cd1 100644
> --- a/drivers/md/dm-zero.c
> +++ b/drivers/md/dm-zero.c
> @@ -26,6 +26,7 @@ static int zero_ctr(struct dm_target *ti, unsigned int argc, char **argv)
> * Silently drop discards, avoiding -EOPNOTSUPP.
> */
> ti->num_discard_bios = 1;
> + ti->may_passthrough_inline_crypto = true;
>
> return 0;
> }
Isn't it wrong to set may_passthrough_inline_crypto on dm-zero? First, there's
no actual underlying device associated with dm-zero, so the idea of dm-zero
"passing through" anything is strange.
Second, inline encryption is supposed to semantically operate on the original
bio. I.e. if someone reads some data from dm-zero and they use a bio_crypt_ctx
that indicates the data should be decrypted, then I'd expect that either the bio
would fail, *or* it would return back data which is equal to the decryption of
the all-zeroes ciphertexts.
may_passthrough_inline_crypto=false would give that behavior. Whereas with
may_passthrough_inline_crypto=true, the bio's encryption context may just be
ignored and reads will return all zeroes.
Of course, setting an encryption context for I/O to/from dm-zero isn't really
something that people would do anyway... But it seems we shouldn't bother
setting may_passthrough_inline_crypto on it when it seems wrong.
- Eric
prev parent reply other threads:[~2020-09-22 0:49 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-09 23:44 [PATCH 0/3] add support for inline encryption to device mapper Satya Tangirala
2020-09-09 23:44 ` [PATCH 1/3] block: keyslot-manager: Introduce passthrough keyslot manager Satya Tangirala
2020-09-22 0:27 ` Eric Biggers
2020-09-09 23:44 ` [PATCH 2/3] dm: add support for passing through inline crypto support Satya Tangirala
2020-09-22 0:32 ` Eric Biggers
2020-09-24 1:14 ` Mike Snitzer
2020-09-24 7:17 ` Satya Tangirala
2020-09-24 13:46 ` Mike Snitzer
2020-09-24 15:45 ` Eric Biggers
2020-09-24 16:16 ` Mike Snitzer
2020-09-24 16:57 ` Eric Biggers
2020-09-24 1:21 ` Mike Snitzer
2020-09-24 7:38 ` Satya Tangirala
2020-09-24 14:23 ` Mike Snitzer
2020-10-15 22:05 ` [dm-devel] " Satya Tangirala
2020-09-24 7:48 ` Satya Tangirala
2020-09-24 13:40 ` Mike Snitzer
2020-10-15 21:55 ` [dm-devel] " Satya Tangirala
2020-09-09 23:44 ` [PATCH 3/3] dm: enable may_passthrough_inline_crypto on some targets Satya Tangirala
2020-09-22 0:49 ` Eric Biggers [this message]
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