[PATCH v5 3/9] block: blk-crypto for Inline Encryption

Satya Tangirala
2019-10-28T07:20:50Z

We introduce blk-crypto, which manages programming keyslots for struct
bios. With blk-crypto, filesystems only need to call bio_crypt_set_ctx with
the encryption key, algorithm and data_unit_num; they don't have to worry
about getting a keyslot for each encryption context, as blk-crypto handles
that. Blk-crypto also makes it possible for layered devices like device
mapper to make use of inline encryption hardware.

Blk-crypto delegates crypto operations to inline encryption hardware when
available, and also contains a software fallback to the kernel crypto API.
For more details, refer to Documentation/block/inline-encryption.rst.

Signed-off-by: Satya Tangirala <satyat@google.com>
---
Documentation/block/index.rst | 1 +
Documentation/block/inline-encryption.rst | 183 +++++
block/Kconfig | 2 +
block/Makefile | 3 +-
block/bio-crypt-ctx.c | 7 +-
block/bio.c | 5 +
block/blk-core.c | 11 +-
block/blk-crypto.c | 798 ++++++++++++++++++++++
include/linux/bio-crypt-ctx.h | 7 +
include/linux/blk-crypto.h | 62 ++
10 files changed, 1076 insertions(+), 3 deletions(-)
create mode 100644 Documentation/block/inline-encryption.rst
create mode 100644 block/blk-crypto.c
create mode 100644 include/linux/blk-crypto.h

diff --git a/Documentation/block/index.rst b/Documentation/block/index.rst
index 3fa7a52fafa4..026addfc69bc 100644
--- a/Documentation/block/index.rst
+++ b/Documentation/block/index.rst
@@ -14,6 +14,7 @@ Block
cmdline-partition
data-integrity
deadline-iosched
+ inline-encryption
ioprio
kyber-iosched
null_blk
diff --git a/Documentation/block/inline-encryption.rst b/Documentation/block/inline-encryption.rst
new file mode 100644
index 000000000000..202826cee95e
--- /dev/null
+++ b/Documentation/block/inline-encryption.rst
@@ -0,0 +1,183 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+=================
+Inline Encryption
+=================
+
+Objective
+=========
+
+We want to support inline encryption (IE) in the kernel.
+To allow for testing, we also want a crypto API fallback when actual
+IE hardware is absent. We also want IE to work with layered devices
+like dm and loopback (i.e. we want to be able to use the IE hardware
+of the underlying devices if present, or else fall back to crypto API
+en/decryption).
+
+
+Constraints and notes
+=====================
+
+- IE hardware have a limited number of "keyslots" that can be programmed
+ with an encryption context (key, algorithm, data unit size, etc.) at any time.
+ One can specify a keyslot in a data request made to the device, and the
+ device will en/decrypt the data using the encryption context programmed into
+ that specified keyslot. When possible, we want to make multiple requests with
+ the same encryption context share the same keyslot.
+
+- We need a way for filesystems to specify an encryption context to use for
+ en/decrypting a struct bio, and a device driver (like UFS) needs to be able
+ to use that encryption context when it processes the bio.
+
+- We need a way for device drivers to expose their capabilities in a unified
+ way to the upper layers.
+
+
+Design
+======
+
+We add a struct bio_crypt_ctx to struct bio that can represent an
+encryption context, because we need to be able to pass this encryption
+context from the FS layer to the device driver to act upon.
+
+While IE hardware works on the notion of keyslots, the FS layer has no
+knowledge of keyslots - it simply wants to specify an encryption context to
+use while en/decrypting a bio.
+
+We introduce a keyslot manager (KSM) that handles the translation from
+encryption contexts specified by the FS to keyslots on the IE hardware.
+This KSM also serves as the way IE hardware can expose their capabilities to
+upper layers. The generic mode of operation is: each device driver that wants
+to support IE will construct a KSM and set it up in its struct request_queue.
+Upper layers that want to use IE on this device can then use this KSM in
+the device's struct request_queue to translate an encryption context into
+a keyslot. The presence of the KSM in the request queue shall be used to mean
+that the device supports IE.
+
+On the device driver end of the interface, the device driver needs to tell the
+KSM how to actually manipulate the IE hardware in the device to do things like
+programming the crypto key into the IE hardware into a particular keyslot. All
+this is achieved through the :c:type:`struct keyslot_mgmt_ll_ops` that the
+device driver passes to the KSM when creating it.
+
+It uses refcounts to track which keyslots are idle (either they have no
+encryption context programmed, or there are no in-flight struct bios
+referencing that keyslot). When a new encryption context needs a keyslot, it
+tries to find a keyslot that has already been programmed with the same
+encryption context, and if there is no such keyslot, it evicts the least
+recently used idle keyslot and programs the new encryption context into that
+one. If no idle keyslots are available, then the caller will sleep until there
+is at least one.
+
+
+Blk-crypto
+==========
+
+The above is sufficient for simple cases, but does not work if there is a
+need for a crypto API fallback, or if we are want to use IE with layered
+devices. To these ends, we introduce blk-crypto. Blk-crypto allows us to
+present a unified view of encryption to the FS (so FS only needs to specify
+an encryption context and not worry about keyslots at all), and blk-crypto
+can decide whether to delegate the en/decryption to IE hardware or to the
+crypto API. Blk-crypto maintains an internal KSM that serves as the crypto
+API fallback.
+
+Blk-crypto needs to ensure that the encryption context is programmed into the
+"correct" keyslot manager for IE. If a bio is submitted to a layered device
+that eventually passes the bio down to a device that really does support IE, we
+want the encryption context to be programmed into a keyslot for the KSM of the
+device with IE support. However, blk-crypto does not know a priori whether a
+particular device is the final device in the layering structure for a bio or
+not. So in the case that a particular device does not support IE, since it is
+possibly the final destination device for the bio, if the bio requires
+encryption (i.e. the bio is doing a write operation), blk-crypto must fallback
+to the crypto API *before* sending the bio to the device.
+
+Blk-crypto ensures that:
+
+- The bio's encryption context is programmed into a keyslot in the KSM of the
+ request queue that the bio is being submitted to (or the crypto API fallback
+ KSM if the request queue doesn't have a KSM), and that the ``processing_ksm``
+ in the ``bi_crypt_context`` is set to this KSM
+
+- That the bio has its own individual reference to the keyslot in this KSM.
+ Once the bio passes through blk-crypto, its encryption context is programmed
+ in some KSM. The "its own individual reference to the keyslot" ensures that
+ keyslots can be released by each bio independently of other bios while
+ ensuring that the bio has a valid reference to the keyslot when, for e.g., the
+ crypto API fallback KSM in blk-crypto performs crypto on the device's behalf.
+ The individual references are ensured by increasing the refcount for the
+ keyslot in the ``processing_ksm`` when a bio with a programmed encryption
+ context is cloned.
+
+
+What blk-crypto does on bio submission
+--------------------------------------
+
+**Case 1:** blk-crypto is given a bio with only an encryption context that hasn't
+been programmed into any keyslot in any KSM (for e.g. a bio from the FS).
+ In this case, blk-crypto will program the encryption context into the KSM of the
+ request queue the bio is being submitted to (and if this KSM does not exist,
+ then it will program it into blk-crypto's internal KSM for crypto API
+ fallback). The KSM that this encryption context was programmed into is stored
+ as the ``processing_ksm`` in the bio's ``bi_crypt_context``.
+
+**Case 2:** blk-crypto is given a bio whose encryption context has already been
+programmed into a keyslot in the *crypto API fallback* KSM.
+ In this case, blk-crypto does nothing; it treats the bio as not having
+ specified an encryption context. Note that we cannot do here what we will do
+ in Case 3 because we would have already encrypted the bio via the crypto API
+ by this point.
+
+**Case 3:** blk-crypto is given a bio whose encryption context has already been
+programmed into a keyslot in some KSM (that is *not* the crypto API fallback
+KSM).
+ In this case, blk-crypto first releases that keyslot from that KSM and then
+ treats the bio as in Case 1.
+
+This way, when a device driver is processing a bio, it can be sure that
+the bio's encryption context has been programmed into some KSM (either the
+device driver's request queue's KSM, or blk-crypto's crypto API fallback KSM).
+It then simply needs to check if the bio's processing_ksm is the device's
+request queue's KSM. If so, then it should proceed with IE. If not, it should
+simply do nothing with respect to crypto, because some other KSM (perhaps the
+blk-crypto crypto API fallback KSM) is handling the en/decryption.
+
+Blk-crypto will release the keyslot that is being held by the bio (and also
+decrypt it if the bio is using the crypto API fallback KSM) once
+``bio_remaining_done`` returns true for the bio.
+
+
+Layered Devices
+===============
+
+Layered devices that wish to support IE need to create their own keyslot
+manager for their request queue, and expose whatever functionality they choose.
+When a layered device wants to pass a bio to another layer (either by
+resubmitting the same bio, or by submitting a clone), it doesn't need to do
+anything special because the bio (or the clone) will once again pass through
+blk-crypto, which will work as described in Case 3. If a layered device wants
+for some reason to do the IO by itself instead of passing it on to a child
+device, but it also chose to expose IE capabilities by setting up a KSM in its
+request queue, it is then responsible for en/decrypting the data itself. In
+such cases, the device can choose to call the blk-crypto function
+``blk_crypto_fallback_to_kernel_crypto_api`` (TODO: Not yet implemented), which will
+cause the en/decryption to be done via the crypto API fallback.
+
+
+Future Optimizations for layered devices
+========================================
+
+Creating a keyslot manager for the layered device uses up memory for each
+keyslot, and in general, a layered device (like dm-linear) merely passes the
+request on to a "child" device, so the keyslots in the layered device itself
+might be completely unused. We can instead define a new type of KSM; the
+"passthrough KSM", that layered devices can use to let blk-crypto know that
+this layered device *will* pass the bio to some child device (and hence
+through blk-crypto again, at which point blk-crypto can program the encryption
+context, instead of programming it into the layered device's KSM). Again, if
+the device "lies" and decides to do the IO itself instead of passing it on to
+a child device, it is responsible for doing the en/decryption (and can choose
+to call ``blk_crypto_fallback_to_kernel_crypto_api``). Another use case for the
+"passthrough KSM" is for IE devices that want to manage their own keyslots/do
+not have a limited number of keyslots.
diff --git a/block/Kconfig b/block/Kconfig
index ae52d42b783b..606a67e47e68 100644
--- a/block/Kconfig
+++ b/block/Kconfig
@@ -179,6 +179,8 @@ config BLK_SED_OPAL

config BLK_INLINE_ENCRYPTION
bool "Enable inline encryption support in block layer"
+ select CRYPTO
+ select CRYPTO_BLKCIPHER
help
Build the blk-crypto subsystem.
Enabling this lets the block layer handle encryption,
diff --git a/block/Makefile b/block/Makefile
index f39611ed151f..8932c7e4fd07 100644
--- a/block/Makefile
+++ b/block/Makefile
@@ -36,4 +36,5 @@ obj-$(CONFIG_BLK_DEBUG_FS) += blk-mq-debugfs.o
obj-$(CONFIG_BLK_DEBUG_FS_ZONED)+= blk-mq-debugfs-zoned.o
obj-$(CONFIG_BLK_SED_OPAL) += sed-opal.o
obj-$(CONFIG_BLK_PM) += blk-pm.o
-obj-$(CONFIG_BLK_INLINE_ENCRYPTION) += keyslot-manager.o bio-crypt-ctx.o
+obj-$(CONFIG_BLK_INLINE_ENCRYPTION) += keyslot-manager.o bio-crypt-ctx.o \
+ blk-crypto.o
diff --git a/block/bio-crypt-ctx.c b/block/bio-crypt-ctx.c
index aa3571f72ee7..6a2b061865c6 100644
--- a/block/bio-crypt-ctx.c
+++ b/block/bio-crypt-ctx.c
@@ -43,7 +43,12 @@ EXPORT_SYMBOL(bio_crypt_free_ctx);

int bio_crypt_clone(struct bio *dst, struct bio *src, gfp_t gfp_mask)
{
- if (!bio_has_crypt_ctx(src))
+ /*
+ * If a bio is swhandled, then it will be decrypted when bio_endio
+ * is called. As we only want the data to be decrypted once, copies
+ * of the bio must not have have a crypt context.
+ */
+ if (!bio_has_crypt_ctx(src) || bio_crypt_swhandled(src))
return 0;

dst->bi_crypt_context = bio_crypt_alloc_ctx(gfp_mask);
diff --git a/block/bio.c b/block/bio.c
index ce8003aadf07..36a1712328d0 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -17,6 +17,7 @@
#include <linux/cgroup.h>
#include <linux/blk-cgroup.h>
#include <linux/highmem.h>
+#include <linux/blk-crypto.h>

#include <trace/events/block.h>
#include "blk.h"
@@ -1788,6 +1789,10 @@ void bio_endio(struct bio *bio)
again:
if (!bio_remaining_done(bio))
return;
+
+ if (!blk_crypto_endio(bio))
+ return;
+
if (!bio_integrity_endio(bio))
return;

diff --git a/block/blk-core.c b/block/blk-core.c
index 3b5959d386fb..0f7e81dbe2ee 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -38,6 +38,7 @@
#include <linux/debugfs.h>
#include <linux/bpf.h>
#include <linux/psi.h>
+#include <linux/blk-crypto.h>

#define CREATE_TRACE_POINTS
#include <trace/events/block.h>
@@ -1061,7 +1062,9 @@ blk_qc_t generic_make_request(struct bio *bio)
/* Create a fresh bio_list for all subordinate requests */
bio_list_on_stack[1] = bio_list_on_stack[0];
bio_list_init(&bio_list_on_stack[0]);
- ret = q->make_request_fn(q, bio);
+
+ if (!blk_crypto_submit_bio(&bio))
+ ret = q->make_request_fn(q, bio);

blk_queue_exit(q);

@@ -1114,6 +1117,9 @@ blk_qc_t direct_make_request(struct bio *bio)
if (!generic_make_request_checks(bio))
return BLK_QC_T_NONE;

+ if (blk_crypto_submit_bio(&bio))
+ return BLK_QC_T_NONE;
+
if (unlikely(blk_queue_enter(q, nowait ? BLK_MQ_REQ_NOWAIT : 0))) {
if (nowait && !blk_queue_dying(q))
bio->bi_status = BLK_STS_AGAIN;
@@ -1810,5 +1816,8 @@ int __init blk_dev_init(void)
if (bio_crypt_ctx_init() < 0)
panic("Failed to allocate mem for bio crypt ctxs\n");

+ if (blk_crypto_init() < 0)
+ panic("Failed to init blk-crypto\n");
+
return 0;
}
diff --git a/block/blk-crypto.c b/block/blk-crypto.c
new file mode 100644
index 000000000000..89649655bf4b
--- /dev/null
+++ b/block/blk-crypto.c
@@ -0,0 +1,798 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright 2019 Google LLC
+ */
+
+/*
+ * Refer to Documentation/block/inline-encryption.rst for detailed explanation.
+ */
+
+#define pr_fmt(fmt) "blk-crypto: " fmt
+
+#include <linux/blk-crypto.h>
+#include <linux/keyslot-manager.h>
+#include <linux/mempool.h>
+#include <linux/blk-cgroup.h>
+#include <linux/crypto.h>
+#include <crypto/skcipher.h>
+#include <crypto/algapi.h>
+#include <linux/module.h>
+#include <linux/sched/mm.h>
+
+/* Represents a crypto mode supported by blk-crypto */
+struct blk_crypto_mode {
+ const char *cipher_str; /* crypto API name (for fallback case) */
+ size_t keysize; /* key size in bytes */
+};
+
+static const struct blk_crypto_mode blk_crypto_modes[] = {
+ [BLK_ENCRYPTION_MODE_AES_256_XTS] = {
+ .cipher_str = "xts(aes)",
+ .keysize = 64,
+ },
+};
+
+static unsigned int num_prealloc_bounce_pg = 32;
+module_param(num_prealloc_bounce_pg, uint, 0);
+MODULE_PARM_DESC(num_prealloc_bounce_pg,
+ "Number of preallocated bounce pages for blk-crypto to use during crypto API fallback encryption");
+
+#define BLK_CRYPTO_MAX_KEY_SIZE 64
+static int blk_crypto_num_keyslots = 100;
+module_param_named(num_keyslots, blk_crypto_num_keyslots, int, 0);
+MODULE_PARM_DESC(num_keyslots,
+ "Number of keyslots for crypto API fallback in blk-crypto.");
+
+static struct blk_crypto_keyslot {
+ struct crypto_skcipher *tfm;
+ enum blk_crypto_mode_num crypto_mode;
+ u8 key[BLK_CRYPTO_MAX_KEY_SIZE];
+ struct crypto_skcipher *tfms[ARRAY_SIZE(blk_crypto_modes)];
+} *blk_crypto_keyslots;
+
+/*
+ * Allocating a crypto tfm during I/O can deadlock, so we have to preallocate
+ * all of a mode's tfms when that mode starts being used. Since each mode may
+ * need all the keyslots at some point, each mode needs its own tfm for each
+ * keyslot; thus, a keyslot may contain tfms for multiple modes. However, to
+ * match the behavior of real inline encryption hardware (which only supports a
+ * single encryption context per keyslot), we only allow one tfm per keyslot to
+ * be used at a time - the rest of the unused tfms have their keys cleared.
+ */
+static struct mutex tfms_lock[ARRAY_SIZE(blk_crypto_modes)];
+static bool tfms_inited[ARRAY_SIZE(blk_crypto_modes)];
+
+struct work_mem {
+ struct work_struct crypto_work;
+ struct bio *bio;
+};
+
+/* The following few vars are only used during the crypto API fallback */
+static struct keyslot_manager *blk_crypto_ksm;
+static struct workqueue_struct *blk_crypto_wq;
+static mempool_t *blk_crypto_page_pool;
+static struct kmem_cache *blk_crypto_work_mem_cache;
+
+bool bio_crypt_swhandled(struct bio *bio)
+{
+ return bio_has_crypt_ctx(bio) &&
+ bio->bi_crypt_context->processing_ksm == blk_crypto_ksm;
+}
+
+static u8 blank_key[BLK_CRYPTO_MAX_KEY_SIZE];
+static void evict_keyslot(unsigned int slot)
+{
+ struct blk_crypto_keyslot *slotp = &blk_crypto_keyslots[slot];
+ enum blk_crypto_mode_num crypto_mode = slotp->crypto_mode;
+ int err;
+
+ WARN_ON(slotp->crypto_mode == BLK_ENCRYPTION_MODE_INVALID);
+
+ /* Clear the key in the skcipher */
+ err = crypto_skcipher_setkey(slotp->tfms[crypto_mode], blank_key,
+ blk_crypto_modes[crypto_mode].keysize);
+ WARN_ON(err);
+ memzero_explicit(slotp->key, BLK_CRYPTO_MAX_KEY_SIZE);
+ slotp->crypto_mode = BLK_ENCRYPTION_MODE_INVALID;
+}
+
+static int blk_crypto_keyslot_program(void *priv, const u8 *key,
+ enum blk_crypto_mode_num crypto_mode,
+ unsigned int data_unit_size,
+ unsigned int slot)
+{
+ struct blk_crypto_keyslot *slotp = &blk_crypto_keyslots[slot];
+ const struct blk_crypto_mode *mode = &blk_crypto_modes[crypto_mode];
+ size_t keysize = mode->keysize;
+ int err;
+
+ if (crypto_mode != slotp->crypto_mode &&
+ slotp->crypto_mode != BLK_ENCRYPTION_MODE_INVALID) {
+ evict_keyslot(slot);
+ }
+
+ if (!slotp->tfms[crypto_mode])
+ return -ENOMEM;
+ slotp->crypto_mode = crypto_mode;
+ err = crypto_skcipher_setkey(slotp->tfms[crypto_mode], key, keysize);
+
+ if (err) {
+ evict_keyslot(slot);
+ return err;
+ }
+
+ memcpy(slotp->key, key, keysize);
+
+ return 0;
+}
+
+static int blk_crypto_keyslot_evict(void *priv, const u8 *key,
+ enum blk_crypto_mode_num crypto_mode,
+ unsigned int data_unit_size,
+ unsigned int slot)
+{
+ evict_keyslot(slot);
+ return 0;
+}
+
+static int blk_crypto_keyslot_find(void *priv,
+ const u8 *key,
+ enum blk_crypto_mode_num crypto_mode,
+ unsigned int data_unit_size_bytes)
+{
+ int slot;
+ const size_t keysize = blk_crypto_modes[crypto_mode].keysize;
+
+ for (slot = 0; slot < blk_crypto_num_keyslots; slot++) {
+ if (blk_crypto_keyslots[slot].crypto_mode == crypto_mode &&
+ !crypto_memneq(blk_crypto_keyslots[slot].key, key, keysize))
+ return slot;
+ }
+
+ return -ENOKEY;
+}
+
+static bool blk_crypto_mode_supported(void *priv,
+ enum blk_crypto_mode_num crypt_mode,
+ unsigned int data_unit_size)
+{
+ /* All blk_crypto_modes are required to have a crypto API fallback. */
+ return true;
+}
+
+/*
+ * The crypto API fallback KSM ops - only used for a bio when it specifies a
+ * blk_crypto_mode for which we failed to get a keyslot in the device's inline
+ * encryption hardware (which probably means the device doesn't have inline
+ * encryption hardware that supports that crypto mode).
+ */
+static const struct keyslot_mgmt_ll_ops blk_crypto_ksm_ll_ops = {
+ .keyslot_program = blk_crypto_keyslot_program,
+ .keyslot_evict = blk_crypto_keyslot_evict,
+ .keyslot_find = blk_crypto_keyslot_find,
+ .crypto_mode_supported = blk_crypto_mode_supported,
+};
+
+static void blk_crypto_encrypt_endio(struct bio *enc_bio)
+{
+ struct bio *src_bio = enc_bio->bi_private;
+ int i;
+
+ for (i = 0; i < enc_bio->bi_vcnt; i++)
+ mempool_free(enc_bio->bi_io_vec[i].bv_page,
+ blk_crypto_page_pool);
+
+ src_bio->bi_status = enc_bio->bi_status;
+
+ bio_put(enc_bio);
+ bio_endio(src_bio);
+}
+
+static struct bio *blk_crypto_clone_bio(struct bio *bio_src)
+{
+ struct bvec_iter iter;
+ struct bio_vec bv;
+ struct bio *bio;
+
+ bio = bio_alloc_bioset(GFP_NOIO, bio_segments(bio_src), NULL);
+ if (!bio)
+ return NULL;
+ bio->bi_disk = bio_src->bi_disk;
+ bio->bi_opf = bio_src->bi_opf;
+ bio->bi_ioprio = bio_src->bi_ioprio;
+ bio->bi_write_hint = bio_src->bi_write_hint;
+ bio->bi_iter.bi_sector = bio_src->bi_iter.bi_sector;
+ bio->bi_iter.bi_size = bio_src->bi_iter.bi_size;
+
+ bio_for_each_segment(bv, bio_src, iter)
+ bio->bi_io_vec[bio->bi_vcnt++] = bv;
+
+ if (bio_integrity(bio_src) &&
+ bio_integrity_clone(bio, bio_src, GFP_NOIO) < 0) {
+ bio_put(bio);
+ return NULL;
+ }
+
+ bio_clone_blkg_association(bio, bio_src);
+ blkcg_bio_issue_init(bio);
+
+ return bio;
+}
+
+/* Check that all I/O segments are data unit aligned */
+static int bio_crypt_check_alignment(struct bio *bio)
+{
+ int data_unit_size = 1 << bio->bi_crypt_context->data_unit_size_bits;
+ struct bvec_iter iter;
+ struct bio_vec bv;
+
+ bio_for_each_segment(bv, bio, iter) {
+ if (!IS_ALIGNED(bv.bv_len | bv.bv_offset, data_unit_size))
+ return -EIO;
+ }
+ return 0;
+}
+
+static int blk_crypto_alloc_cipher_req(struct bio *src_bio,
+ struct skcipher_request **ciph_req_ptr,
+ struct crypto_wait *wait)
+{
+ int slot;
+ struct skcipher_request *ciph_req;
+ struct blk_crypto_keyslot *slotp;
+
+ slot = bio_crypt_get_keyslot(src_bio);
+ slotp = &blk_crypto_keyslots[slot];
+ ciph_req = skcipher_request_alloc(slotp->tfms[slotp->crypto_mode],
+ GFP_NOIO);
+ if (!ciph_req) {
+ src_bio->bi_status = BLK_STS_RESOURCE;
+ return -ENOMEM;
+ }
+
+ skcipher_request_set_callback(ciph_req,
+ CRYPTO_TFM_REQ_MAY_BACKLOG |
+ CRYPTO_TFM_REQ_MAY_SLEEP,
+ crypto_req_done, wait);
+ *ciph_req_ptr = ciph_req;
+ return 0;
+}
+
+static int blk_crypto_split_bio_if_needed(struct bio **bio_ptr)
+{
+ struct bio *bio = *bio_ptr;
+ unsigned int i = 0;
+ unsigned int num_sectors = 0;
+ struct bio_vec bv;
+ struct bvec_iter iter;
+
+ bio_for_each_segment(bv, bio, iter) {
+ num_sectors += bv.bv_len >> SECTOR_SHIFT;
+ if (++i == BIO_MAX_PAGES)
+ break;
+ }
+ if (num_sectors < bio_sectors(bio)) {
+ struct bio *split_bio;
+
+ split_bio = bio_split(bio, num_sectors, GFP_NOIO, NULL);
+ if (!split_bio) {
+ bio->bi_status = BLK_STS_RESOURCE;
+ return -ENOMEM;
+ }
+ bio_chain(split_bio, bio);
+ generic_make_request(bio);
+ *bio_ptr = split_bio;
+ }
+ return 0;
+}
+
+/*
+ * The crypto API fallback's encryption routine.
+ * Allocate a bounce bio for encryption, encrypt the input bio using
+ * crypto API, and replace *bio_ptr with the bounce bio. May split input
+ * bio if it's too large.
+ */
+static int blk_crypto_encrypt_bio(struct bio **bio_ptr)
+{
+ struct bio *src_bio;
+ struct skcipher_request *ciph_req = NULL;
+ DECLARE_CRYPTO_WAIT(wait);
+ int err = 0;
+ u64 curr_dun;
+ union {
+ __le64 dun;
+ u8 bytes[16];
+ } iv;
+ struct scatterlist src, dst;
+ struct bio *enc_bio;
+ struct bio_vec *enc_bvec;
+ int i, j;
+ int data_unit_size;
+
+ /* Split the bio if it's too big for single page bvec */
+ err = blk_crypto_split_bio_if_needed(bio_ptr);
+ if (err)
+ return err;
+
+ src_bio = *bio_ptr;
+ data_unit_size = 1 << src_bio->bi_crypt_context->data_unit_size_bits;
+
+ /* Allocate bounce bio for encryption */
+ enc_bio = blk_crypto_clone_bio(src_bio);
+ if (!enc_bio) {
+ src_bio->bi_status = BLK_STS_RESOURCE;
+ return -ENOMEM;
+ }
+
+ /*
+ * Use the crypto API fallback keyslot manager to get a crypto_skcipher
+ * for the algorithm and key specified for this bio.
+ */
+ err = bio_crypt_ctx_acquire_keyslot(src_bio, blk_crypto_ksm);
+ if (err) {
+ src_bio->bi_status = BLK_STS_IOERR;
+ goto out_put_enc_bio;
+ }
+
+ /* and then allocate an skcipher_request for it */
+ err = blk_crypto_alloc_cipher_req(src_bio, &ciph_req, &wait);
+ if (err)
+ goto out_release_keyslot;
+
+ curr_dun = bio_crypt_data_unit_num(src_bio);
+ sg_init_table(&src, 1);
+ sg_init_table(&dst, 1);
+
+ skcipher_request_set_crypt(ciph_req, &src, &dst,
+ data_unit_size, iv.bytes);
+
+ /* Encrypt each page in the bounce bio */
+ for (i = 0, enc_bvec = enc_bio->bi_io_vec; i < enc_bio->bi_vcnt;
+ enc_bvec++, i++) {
+ struct page *plaintext_page = enc_bvec->bv_page;
+ struct page *ciphertext_page =
+ mempool_alloc(blk_crypto_page_pool, GFP_NOIO);
+
+ enc_bvec->bv_page = ciphertext_page;
+
+ if (!ciphertext_page) {
+ src_bio->bi_status = BLK_STS_RESOURCE;
+ err = -ENOMEM;
+ goto out_free_bounce_pages;
+ }
+
+ sg_set_page(&src, plaintext_page, data_unit_size,
+ enc_bvec->bv_offset);
+ sg_set_page(&dst, ciphertext_page, data_unit_size,
+ enc_bvec->bv_offset);
+
+ /* Encrypt each data unit in this page */
+ for (j = 0; j < enc_bvec->bv_len; j += data_unit_size) {
+ memset(&iv, 0, sizeof(iv));
+ iv.dun = cpu_to_le64(curr_dun);
+
+ err = crypto_wait_req(crypto_skcipher_encrypt(ciph_req),
+ &wait);
+ if (err) {
+ i++;
+ src_bio->bi_status = BLK_STS_RESOURCE;
+ goto out_free_bounce_pages;
+ }
+ curr_dun++;
+ src.offset += data_unit_size;
+ dst.offset += data_unit_size;
+ }
+ }
+
+ enc_bio->bi_private = src_bio;
+ enc_bio->bi_end_io = blk_crypto_encrypt_endio;
+ *bio_ptr = enc_bio;
+
+ enc_bio = NULL;
+ err = 0;
+ goto out_free_ciph_req;
+
+out_free_bounce_pages:
+ while (i > 0)
+ mempool_free(enc_bio->bi_io_vec[--i].bv_page,
+ blk_crypto_page_pool);
+out_free_ciph_req:
+ skcipher_request_free(ciph_req);
+out_release_keyslot:
+ bio_crypt_ctx_release_keyslot(src_bio);
+out_put_enc_bio:
+ if (enc_bio)
+ bio_put(enc_bio);
+
+ return err;
+}
+
+/*
+ * The crypto API fallback's main decryption routine.
+ * Decrypts input bio in place.
+ */
+static void blk_crypto_decrypt_bio(struct work_struct *w)
+{
+ struct work_mem *work_mem =
+ container_of(w, struct work_mem, crypto_work);
+ struct bio *bio = work_mem->bio;
+ struct skcipher_request *ciph_req = NULL;
+ DECLARE_CRYPTO_WAIT(wait);
+ struct bio_vec bv;
+ struct bvec_iter iter;
+ u64 curr_dun;
+ union {
+ __le64 dun;
+ u8 bytes[16];
+ } iv;
+ struct scatterlist sg;
+ int data_unit_size = 1 << bio->bi_crypt_context->data_unit_size_bits;
+ int i;
+ int err;
+
+ /*
+ * Use the crypto API fallback keyslot manager to get a crypto_skcipher
+ * for the algorithm and key specified for this bio.
+ */
+ if (bio_crypt_ctx_acquire_keyslot(bio, blk_crypto_ksm)) {
+ bio->bi_status = BLK_STS_RESOURCE;
+ goto out_no_keyslot;
+ }
+
+ /* and then allocate an skcipher_request for it */
+ err = blk_crypto_alloc_cipher_req(bio, &ciph_req, &wait);
+ if (err)
+ goto out;
+
+ curr_dun = bio_crypt_sw_data_unit_num(bio);
+ sg_init_table(&sg, 1);
+ skcipher_request_set_crypt(ciph_req, &sg, &sg, data_unit_size,
+ iv.bytes);
+
+ /* Decrypt each segment in the bio */
+ __bio_for_each_segment(bv, bio, iter,
+ bio->bi_crypt_context->crypt_iter) {
+ struct page *page = bv.bv_page;
+
+ sg_set_page(&sg, page, data_unit_size, bv.bv_offset);
+
+ /* Decrypt each data unit in the segment */
+ for (i = 0; i < bv.bv_len; i += data_unit_size) {
+ memset(&iv, 0, sizeof(iv));
+ iv.dun = cpu_to_le64(curr_dun);
+ if (crypto_wait_req(crypto_skcipher_decrypt(ciph_req),
+ &wait)) {
+ bio->bi_status = BLK_STS_IOERR;
+ goto out;
+ }
+ curr_dun++;
+ sg.offset += data_unit_size;
+ }
+ }
+
+out:
+ skcipher_request_free(ciph_req);
+ bio_crypt_ctx_release_keyslot(bio);
+out_no_keyslot:
+ kmem_cache_free(blk_crypto_work_mem_cache, work_mem);
+ bio_endio(bio);
+}
+
+/* Queue bio for decryption */
+static void blk_crypto_queue_decrypt_bio(struct bio *bio)
+{
+ struct work_mem *work_mem =
+ kmem_cache_zalloc(blk_crypto_work_mem_cache, GFP_ATOMIC);
+
+ if (!work_mem) {
+ bio->bi_status = BLK_STS_RESOURCE;
+ bio_endio(bio);
+ return;
+ }
+
+ INIT_WORK(&work_mem->crypto_work, blk_crypto_decrypt_bio);
+ work_mem->bio = bio;
+ queue_work(blk_crypto_wq, &work_mem->crypto_work);
+}
+
+/**
+ * blk_crypto_submit_bio - handle submitting bio for inline encryption
+ *
+ * @bio_ptr: pointer to original bio pointer
+ *
+ * If the bio doesn't have inline encryption enabled or the submitter already
+ * specified a keyslot for the target device, do nothing. Else, a raw key must
+ * have been provided, so acquire a device keyslot for it if supported. Else,
+ * use the crypto API fallback.
+ *
+ * When the crypto API fallback is used for encryption, blk-crypto may choose to
+ * split the bio into 2 - the first one that will continue to be processed and
+ * the second one that will be resubmitted via generic_make_request.
+ * A bounce bio will be allocated to encrypt the contents of the aforementioned
+ * "first one", and *bio_ptr will be updated to this bounce bio.
+ *
+ * Return: 0 if bio submission should continue; nonzero if bio_endio() was
+ * already called so bio submission should abort.
+ */
+int blk_crypto_submit_bio(struct bio **bio_ptr)
+{
+ struct bio *bio = *bio_ptr;
+ struct request_queue *q;
+ int err;
+ struct bio_crypt_ctx *crypt_ctx;
+
+ if (!bio_has_crypt_ctx(bio) || !bio_has_data(bio))
+ return 0;
+
+ /*
+ * When a read bio is marked for sw decryption, its bi_iter is saved
+ * so that when we decrypt the bio later, we know what part of it was
+ * marked for sw decryption (when the bio is passed down after
+ * blk_crypto_submit bio, it may be split or advanced so we cannot rely
+ * on the bi_iter while decrypting in blk_crypto_endio)
+ */
+ if (bio_crypt_swhandled(bio))
+ return 0;
+
+ err = bio_crypt_check_alignment(bio);
+ if (err) {
+ bio->bi_status = BLK_STS_IOERR;
+ goto out;
+ }
+
+ crypt_ctx = bio->bi_crypt_context;
+ q = bio->bi_disk->queue;
+
+ if (bio_crypt_has_keyslot(bio)) {
+ /* Key already programmed into device? */
+ if (q->ksm == crypt_ctx->processing_ksm)
+ return 0;
+
+ /* Nope, release the existing keyslot. */
+ bio_crypt_ctx_release_keyslot(bio);
+ }
+
+ /* Get device keyslot if supported */
+ if (q->ksm) {
+ err = bio_crypt_ctx_acquire_keyslot(bio, q->ksm);
+ if (!err)
+ return 0;
+
+ pr_warn_once("Failed to acquire keyslot for %s (err=%d). Falling back to crypto API.\n",
+ bio->bi_disk->disk_name, err);
+ }
+
+ /* Fallback to crypto API */
+ if (!READ_ONCE(tfms_inited[bio->bi_crypt_context->crypto_mode])) {
+ err = -EIO;
+ bio->bi_status = BLK_STS_IOERR;
+ goto out;
+ }
+
+ if (bio_data_dir(bio) == WRITE) {
+ /* Encrypt the data now */
+ err = blk_crypto_encrypt_bio(bio_ptr);
+ if (err)
+ goto out;
+ } else {
+ /* Mark bio as swhandled */
+ bio->bi_crypt_context->processing_ksm = blk_crypto_ksm;
+ bio->bi_crypt_context->crypt_iter = bio->bi_iter;
+ bio->bi_crypt_context->sw_data_unit_num =
+ bio->bi_crypt_context->data_unit_num;
+ }
+ return 0;
+out:
+ bio_endio(*bio_ptr);
+ return err;
+}
+
+/**
+ * blk_crypto_endio - clean up bio w.r.t inline encryption during bio_endio
+ *
+ * @bio - the bio to clean up
+ *
+ * If blk_crypto_submit_bio decided to fallback to crypto API for this
+ * bio, we queue the bio for decryption into a workqueue and return false,
+ * and call bio_endio(bio) at a later time (after the bio has been decrypted).
+ *
+ * If the bio is not to be decrypted by the crypto API, this function releases
+ * the reference to the keyslot that blk_crypto_submit_bio got.
+ *
+ * Return: true if bio_endio should continue; false otherwise (bio_endio will
+ * be called again when bio has been decrypted).
+ */
+bool blk_crypto_endio(struct bio *bio)
+{
+ if (!bio_has_crypt_ctx(bio))
+ return true;
+
+ if (bio_crypt_swhandled(bio)) {
+ /*
+ * The only bios that are swhandled when they reach here
+ * are those with bio_data_dir(bio) == READ, since WRITE
+ * bios that are encrypted by the crypto API fallback are
+ * handled by blk_crypto_encrypt_endio.
+ */
+
+ /* If there was an IO error, don't decrypt. */
+ if (bio->bi_status)
+ return true;
+
+ blk_crypto_queue_decrypt_bio(bio);
+ return false;
+ }
+
+ if (bio_crypt_has_keyslot(bio))
+ bio_crypt_ctx_release_keyslot(bio);
+
+ return true;
+}
+
+/**
+ * blk_crypto_start_using_mode() - Allocate skciphers for a
+ * mode_num for all keyslots
+ * @mode_num - the blk_crypto_mode we want to allocate ciphers for.
+ *
+ * Upper layers (filesystems) should call this function to ensure that a
+ * the crypto API fallback has transforms for this algorithm, if they become
+ * necessary.
+ *
+ * Return: 0 on success and -err on error.
+ */
+int blk_crypto_start_using_mode(enum blk_crypto_mode_num mode_num,
+ unsigned int data_unit_size,
+ struct request_queue *q)
+{
+ struct blk_crypto_keyslot *slotp;
+ int err = 0;
+ int i;
+
+ /*
+ * Fast path
+ * Ensure that updates to blk_crypto_keyslots[i].tfms[mode_num]
+ * for each i are visible before we try to access them.
+ */
+ if (likely(smp_load_acquire(&tfms_inited[mode_num])))
+ return 0;
+
+ /*
+ * If the keyslot manager of the request queue supports this
+ * crypto mode, then we don't need to allocate this mode.
+ */
+ if (keyslot_manager_crypto_mode_supported(q->ksm, mode_num,
+ data_unit_size)) {
+ return 0;
+ }
+
+ mutex_lock(&tfms_lock[mode_num]);
+ if (likely(tfms_inited[mode_num]))
+ goto out;
+
+ for (i = 0; i < blk_crypto_num_keyslots; i++) {
+ slotp = &blk_crypto_keyslots[i];
+ slotp->tfms[mode_num] = crypto_alloc_skcipher(
+ blk_crypto_modes[mode_num].cipher_str,
+ 0, 0);
+ if (IS_ERR(slotp->tfms[mode_num])) {
+ err = PTR_ERR(slotp->tfms[mode_num]);
+ slotp->tfms[mode_num] = NULL;
+ goto out_free_tfms;
+ }
+
+ crypto_skcipher_set_flags(slotp->tfms[mode_num],
+ CRYPTO_TFM_REQ_FORBID_WEAK_KEYS);
+ }
+
+ /*
+ * Ensure that updates to blk_crypto_keyslots[i].tfms[mode_num]
+ * for each i are visible before we set tfms_inited[mode_num].
+ */
+ smp_store_release(&tfms_inited[mode_num], true);
+ goto out;
+
+out_free_tfms:
+ for (i = 0; i < blk_crypto_num_keyslots; i++) {
+ slotp = &blk_crypto_keyslots[i];
+ crypto_free_skcipher(slotp->tfms[mode_num]);
+ slotp->tfms[mode_num] = NULL;
+ }
+out:
+ mutex_unlock(&tfms_lock[mode_num]);
+ return err;
+}
+EXPORT_SYMBOL(blk_crypto_start_using_mode);
+
+/**
+ * blk_crypto_evict_key() - Evict a key from any inline encryption hardware
+ * it may have been programmed into
+ * @q - The request queue who's keyslot manager this key might have been
+ * programmed into
+ * @key - The key to evict
+ * @mode - The blk_crypto_mode_num used with this key
+ * @data_unit_size - The data unit size used with this key
+ *
+ * Upper layers (filesystems) should call this function to ensure that a key
+ * is evicted from hardware that it might have been programmed into. This
+ * will call keyslot_manager_evict_key on the queue's keyslot manager, if one
+ * exists, and supports the crypto algorithm with the specified data unit size.
+ * Otherwise, it will evict the key from the blk_crypto_ksm.
+ *
+ * Return: 0 on success, -err on error.
+ */
+int blk_crypto_evict_key(struct request_queue *q, const u8 *key,
+ enum blk_crypto_mode_num mode,
+ unsigned int data_unit_size)
+{
+ struct keyslot_manager *ksm = blk_crypto_ksm;
+
+ if (q && q->ksm && keyslot_manager_crypto_mode_supported(q->ksm, mode,
+ data_unit_size)) {
+ ksm = q->ksm;
+ }
+
+ return keyslot_manager_evict_key(ksm, key, mode, data_unit_size);
+}
+EXPORT_SYMBOL(blk_crypto_evict_key);
+
+int __init blk_crypto_init(void)
+{
+ int i;
+ int err = -ENOMEM;
+
+ prandom_bytes(blank_key, BLK_CRYPTO_MAX_KEY_SIZE);
+
+ blk_crypto_ksm = keyslot_manager_create(blk_crypto_num_keyslots,
+ &blk_crypto_ksm_ll_ops,
+ NULL);
+ if (!blk_crypto_ksm)
+ goto out;
+
+ blk_crypto_wq = alloc_workqueue("blk_crypto_wq",
+ WQ_UNBOUND | WQ_HIGHPRI |
+ WQ_MEM_RECLAIM,
+ num_online_cpus());
+ if (!blk_crypto_wq)
+ goto out_free_ksm;
+
+ blk_crypto_keyslots = kcalloc(blk_crypto_num_keyslots,
+ sizeof(*blk_crypto_keyslots),
+ GFP_KERNEL);
+ if (!blk_crypto_keyslots)
+ goto out_free_workqueue;
+
+ for (i = 0; i < blk_crypto_num_keyslots; i++) {
+ blk_crypto_keyslots[i].crypto_mode =
+ BLK_ENCRYPTION_MODE_INVALID;
+ }
+
+ for (i = 0; i < ARRAY_SIZE(blk_crypto_modes); i++)
+ mutex_init(&tfms_lock[i]);
+
+ blk_crypto_page_pool =
+ mempool_create_page_pool(num_prealloc_bounce_pg, 0);
+ if (!blk_crypto_page_pool)
+ goto out_free_keyslots;
+
+ blk_crypto_work_mem_cache = KMEM_CACHE(work_mem, SLAB_RECLAIM_ACCOUNT);
+ if (!blk_crypto_work_mem_cache)
+ goto out_free_page_pool;
+
+ return 0;
+
+out_free_page_pool:
+ mempool_destroy(blk_crypto_page_pool);
+ blk_crypto_page_pool = NULL;
+out_free_keyslots:
+ kzfree(blk_crypto_keyslots);
+ blk_crypto_keyslots = NULL;
+out_free_workqueue:
+ destroy_workqueue(blk_crypto_wq);
+ blk_crypto_wq = NULL;
+out_free_ksm:
+ keyslot_manager_destroy(blk_crypto_ksm);
+ blk_crypto_ksm = NULL;
+out:
+ pr_warn("No memory for blk-crypto crypto API fallback.");
+ return err;
+}
diff --git a/include/linux/bio-crypt-ctx.h b/include/linux/bio-crypt-ctx.h
index 5cd569f77c31..7c389f310bab 100644
--- a/include/linux/bio-crypt-ctx.h
+++ b/include/linux/bio-crypt-ctx.h
@@ -53,6 +53,8 @@ static inline void bio_crypt_advance(struct bio *bio, unsigned int bytes)
}
}

+extern bool bio_crypt_swhandled(struct bio *bio);
+
static inline bool bio_crypt_has_keyslot(struct bio *bio)
{
return bio->bi_crypt_context->keyslot >= 0;
@@ -170,6 +172,11 @@ static inline void bio_crypt_set_ctx(struct bio *bio,
unsigned int dun_bits,
gfp_t gfp_mask) { }

+static inline bool bio_crypt_swhandled(struct bio *bio)
+{
+ return false;
+}
+
static inline void bio_set_data_unit_num(struct bio *bio, u64 dun) { }

static inline bool bio_crypt_has_keyslot(struct bio *bio)
diff --git a/include/linux/blk-crypto.h b/include/linux/blk-crypto.h
new file mode 100644
index 000000000000..2a07401244a6
--- /dev/null
+++ b/include/linux/blk-crypto.h
@@ -0,0 +1,62 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright 2019 Google LLC
+ */
+
+#ifndef __LINUX_BLK_CRYPTO_H
+#define __LINUX_BLK_CRYPTO_H
+
+#include <linux/types.h>
+#include <linux/bio.h>
+
+#ifdef CONFIG_BLK_INLINE_ENCRYPTION
+
+int blk_crypto_init(void);
+
+int blk_crypto_submit_bio(struct bio **bio_ptr);
+
+bool blk_crypto_endio(struct bio *bio);
+
+int blk_crypto_start_using_mode(enum blk_crypto_mode_num mode_num,
+ unsigned int data_unit_size,
+ struct request_queue *q);
+
+int blk_crypto_evict_key(struct request_queue *q, const u8 *key,
+ enum blk_crypto_mode_num mode,
+ unsigned int data_unit_size);
+
+#else /* CONFIG_BLK_INLINE_ENCRYPTION */
+
+static inline int blk_crypto_init(void)
+{
+ return 0;
+}
+
+static inline int blk_crypto_submit_bio(struct bio **bio_ptr)
+{
+ return 0;
+}
+
+static inline bool blk_crypto_endio(struct bio *bio)
+{
+ return true;
+}
+
+static inline int
+blk_crypto_start_using_mode(enum blk_crypto_mode_num mode_num,
+ unsigned int data_unit_size,
+ struct request_queue *q)
+{
+ return -EOPNOTSUPP;
+}
+
+static inline int blk_crypto_evict_key(struct request_queue *q, const u8 *key,
+ enum blk_crypto_mode_num mode,
+ unsigned int data_unit_size)
+{
+ return 0;
+}
+
+#endif /* CONFIG_BLK_INLINE_ENCRYPTION */
+
+#endif /* __LINUX_BLK_CRYPTO_H */
--
2.24.0.rc0.303.g954a862665-goog