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 a private field to struct blk_keyslot_manager that owners of the struct can use for any purpose. The struct blk_keyslot_manager has been embedded within other structures directly (like in struct ufs_hba in drivers/scsi/ufs/ufshcd.h), but we don't want to do that with struct mapped_device. So, the device mapper patches later in this series use the private field to hold a pointer to the associated struct mapped_device, since we can't use container_of() anymore. 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 that it "may_passthrough_inline_crypto" 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 DM device's keyslot manager is set up whenever a new table is swapped in. This patch only allows the keyslot manager's capabilities to *expand* because of table changes. Any attempts to load a new table that would cause crypto capabilities to be dropped are rejected. The crypto capabilities of a new table are also verified when the table is loaded (and the load is rejected if crypto capabilities will be dropped because of the new table), but the keyslot manager for the DM device is only modified when the table is actually swapped in. 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 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 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 (4): block: keyslot-manager: Introduce passthrough keyslot manager block: add private field to struct keyslot_manager dm: add support for passing through inline crypto support dm: enable may_passthrough_inline_crypto on some targets block/blk-crypto.c | 1 + block/keyslot-manager.c | 130 +++++++++++++++++++ drivers/md/dm-flakey.c | 1 + drivers/md/dm-ioctl.c | 8 ++ drivers/md/dm-linear.c | 1 + drivers/md/dm.c | 217 +++++++++++++++++++++++++++++++- drivers/md/dm.h | 19 +++ include/linux/device-mapper.h | 6 + include/linux/keyslot-manager.h | 22 ++++ 9 files changed, 404 insertions(+), 1 deletion(-) -- 2.29.0.rc1.297.gfa9743e501-goog
