On Mon, Feb 01 2021 at 12:10am -0500, Satya Tangirala <satyat@xxxxxxxxxx> wrote: > This patch series adds support for inline encryption to the device mapper. > > Patch 1 introduces the "passthrough" keyslot manager. > > The regular keyslot manager is designed for inline encryption hardware that > have only a small fixed number of keyslots. A DM device itself does not > actually have only a small fixed number of keyslots - it doesn't actually > have any keyslots in the first place, and programming an encryption context > into a DM device doesn't make much semantic sense. It is possible for a DM > device to set up a keyslot manager with some "sufficiently large" number of > keyslots in its request queue, so that upper layers can use the inline > encryption capabilities of the DM device's underlying devices, but the > memory being allocated for the DM device's keyslots is a waste since they > won't actually be used by the DM device. > > The passthrough keyslot manager solves this issue - when the block layer > sees that a request queue has a passthrough keyslot manager, it doesn't > attempt to program any encryption context into the keyslot manager. The > passthrough keyslot manager only allows the device to expose its inline > encryption capabilities, and a way for upper layers to evict keys if > necessary. > > There also exist inline encryption hardware that can handle encryption > contexts directly, and allow users to pass them a data request along with > the encryption context (as opposed to inline encryption hardware that > require users to first program a keyslot with an encryption context, and > then require the users to pass the keyslot index with the data request). > Such devices can also make use of the passthrough keyslot manager. > > Patch 2 introduces some keyslot manager functions useful for the device > mapper. > > Patch 3 introduces the changes for inline encryption support for the device > mapper. A DM device only exposes the intersection of the crypto > capabilities of its underlying devices. This is so that in case a bio with > an encryption context is eventually mapped to an underlying device that > doesn't support that encryption context, the blk-crypto-fallback's cipher > tfms are allocated ahead of time by the call to blk_crypto_start_using_key. > > Each DM target can now also specify the "DM_TARGET_PASSES_CRYPTO" flag in > the target type features to opt-in to supporting passing through the > underlying inline encryption capabilities. This flag is needed because it > doesn't make much semantic sense for certain targets like dm-crypt to > expose the underlying inline encryption capabilities to the upper layers. > Again, the DM exposes inline encryption capabilities of the underlying > devices only if all of them opt-in to passing through inline encryption > support. > > A keyslot manager is created for a table when it is loaded. However, the > mapped device's exposed capabilities *only* updated once the table is > swapped in (until the new table is swapped in, the mapped device continues > to expose the old table's crypto capabilities). > > This patch only allows the keyslot manager's capabilities to *expand* > because of table changes. Any attempt to load a new table that doesn't > support a crypto capability that the old table did is rejected. > > This patch also only exposes the intersection of the underlying device's > capabilities, which has the effect of causing en/decryption of a bio to > fall back to the kernel crypto API (if the fallback is enabled) whenever > any of the underlying devices doesn't support the encryption context of the > bio - it might be possible to make the bio only fall back to the kernel > crypto API if the bio's target underlying device doesn't support the bio's > encryption context, but the use case may be uncommon enough in the first > place not to warrant worrying about it right now. > > Patch 4 makes DM evict a key from all its underlying devices when asked to > evict a key. > > Patch 5 makes some DM targets opt-in to passing through inline encryption > support. It does not (yet) try to enable this option with dm-raid, since > users can "hot add" disks to a raid device, which makes this not completely > straightforward (we'll need to ensure that any "hot added" disks must have > a superset of the inline encryption capabilities of the rest of the disks > in the raid device, due to the way Patch 2 of this series works). > > Changes v3 => v4: > - Allocate the memory for the ksm of the mapped device in > dm_table_complete(), and install the ksm in the md queue in __bind() > (as suggested by Mike). Also drop patch 5 from v3 since it's no longer > needed. > - Some cleanups > > Changes v2 => v3: > - Split up the main DM patch into 4 separate patches > - Removed the priv variable added to struct keyslot manager in v2 > - Use a flag in target type features for opting-in to inline encryption > support, instead of using "may_passthrough_inline_crypto" > - cleanups, improve docs and restructure code > > Changes v1 => v2: > - Introduce private field to struct blk_keyslot_manager > - Allow the DM keyslot manager to expand its crypto capabilities if the > table is changed. > - Make DM reject table changes that would otherwise cause crypto > capabilities to be dropped. > - Allocate the DM device's keyslot manager only when at least one crypto > capability is supported (since a NULL value for q->ksm represents "no > crypto support" anyway). > - Remove the struct blk_keyslot_manager field from struct mapped_device. > This patch now relies on just directly setting up the keyslot manager in > the request queue, since each DM device is tied to only 1 queue. > > Satya Tangirala (5): > block: keyslot-manager: Introduce passthrough keyslot manager > block: keyslot-manager: Introduce functions for device mapper support > dm: add support for passing through inline crypto support > dm: support key eviction from keyslot managers of underlying devices > dm: set DM_TARGET_PASSES_CRYPTO feature for some targets > > block/blk-crypto.c | 1 + > block/keyslot-manager.c | 146 ++++++++++++++++++++++ > drivers/md/dm-core.h | 5 + > drivers/md/dm-flakey.c | 4 +- > drivers/md/dm-linear.c | 5 +- > drivers/md/dm-table.c | 210 ++++++++++++++++++++++++++++++++ > drivers/md/dm.c | 18 ++- > include/linux/device-mapper.h | 11 ++ > include/linux/keyslot-manager.h | 11 ++ > 9 files changed, 407 insertions(+), 4 deletions(-) > > -- > 2.30.0.365.g02bc693789-goog > This set looks good to me now. To avoid DM needing another rebase on block: Jens (and others), would you like to review patches 1 and 2 (and reply with your Reviewed-by) so I could pickup the DM required keyslot-manager changes along with patches 3-5? Thanks, Mike -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
