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FROMLIST: block: blk-crypto for Inline Encryption

Browse Source 
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.

Bug: 137270441
Test: tested as series; see Ie1b77f7615d6a7a60fdc9105c7ab2200d17636a8
Change-Id: I7df59fef0c1e90043b1899c5a95973e23afac0c5
Signed-off-by: Satya Tangirala <satyat@google.com>
Link: https://patchwork.kernel.org/patch/11214731/
This commit is contained in:
Satya Tangirala
2019-10-24 14:44:25 -07:00
committed by Paul Lawrence
parent d85bf5e127
commit 600e29fce0
10 changed files with 1076 additions and 3 deletions
Download Patch File Download Diff File Expand all files Collapse all files

1
Documentation/block/index.rst
View File

@@ -14,6 +14,7 @@ Block
cmdline-partition cmdline-partition
data-integrity data-integrity
deadline-iosched deadline-iosched
inline-encryption
ioprio ioprio
kyber-iosched kyber-iosched
null_blk null_blk

183
Documentation/block/inline-encryption.rst Normal file
View File

@@ -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.

2
block/Kconfig
View File

@@ -179,6 +179,8 @@ config BLK_SED_OPAL
config BLK_INLINE_ENCRYPTION config BLK_INLINE_ENCRYPTION
bool "Enable inline encryption support in block layer" bool "Enable inline encryption support in block layer"
select CRYPTO
select CRYPTO_BLKCIPHER
help help
Build the blk-crypto subsystem. Build the blk-crypto subsystem.
Enabling this lets the block layer handle encryption, Enabling this lets the block layer handle encryption,

3
block/Makefile
View File

@@ -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-$(CONFIG_BLK_DEBUG_FS_ZONED)+= blk-mq-debugfs-zoned.o
obj-$(CONFIG_BLK_SED_OPAL) += sed-opal.o obj-$(CONFIG_BLK_SED_OPAL) += sed-opal.o
obj-$(CONFIG_BLK_PM) += blk-pm.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

7
block/bio-crypt-ctx.c
View File

@@ -43,7 +43,12 @@ EXPORT_SYMBOL(bio_crypt_free_ctx);
int bio_crypt_clone(struct bio *dst, struct bio *src, gfp_t gfp_mask) 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; return 0;
dst->bi_crypt_context = bio_crypt_alloc_ctx(gfp_mask); dst->bi_crypt_context = bio_crypt_alloc_ctx(gfp_mask);

5
block/bio.c
View File

@@ -17,6 +17,7 @@
#include <linux/cgroup.h> #include <linux/cgroup.h>
#include <linux/blk-cgroup.h> #include <linux/blk-cgroup.h>
#include <linux/highmem.h> #include <linux/highmem.h>
#include <linux/blk-crypto.h>
#include <trace/events/block.h> #include <trace/events/block.h>
#include "blk.h" #include "blk.h"
@@ -1788,6 +1789,10 @@ void bio_endio(struct bio *bio)
again: again:
if (!bio_remaining_done(bio)) if (!bio_remaining_done(bio))
return; return;
if (!blk_crypto_endio(bio))
return;
if (!bio_integrity_endio(bio)) if (!bio_integrity_endio(bio))
return; return;

9
block/blk-core.c
View File

@@ -38,6 +38,7 @@
#include <linux/debugfs.h> #include <linux/debugfs.h>
#include <linux/bpf.h> #include <linux/bpf.h>
#include <linux/psi.h> #include <linux/psi.h>
#include <linux/blk-crypto.h>
#define CREATE_TRACE_POINTS #define CREATE_TRACE_POINTS
#include <trace/events/block.h> #include <trace/events/block.h>
@@ -1061,6 +1062,8 @@ blk_qc_t generic_make_request(struct bio *bio)
/* Create a fresh bio_list for all subordinate requests */ /* Create a fresh bio_list for all subordinate requests */
bio_list_on_stack[1] = bio_list_on_stack[0]; bio_list_on_stack[1] = bio_list_on_stack[0];
bio_list_init(&bio_list_on_stack[0]); bio_list_init(&bio_list_on_stack[0]);
if (!blk_crypto_submit_bio(&bio))
ret = q->make_request_fn(q, bio); ret = q->make_request_fn(q, bio);
blk_queue_exit(q); blk_queue_exit(q);
@@ -1114,6 +1117,9 @@ blk_qc_t direct_make_request(struct bio *bio)
if (!generic_make_request_checks(bio)) if (!generic_make_request_checks(bio))
return BLK_QC_T_NONE; 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 (unlikely(blk_queue_enter(q, nowait ? BLK_MQ_REQ_NOWAIT : 0))) {
if (nowait && !blk_queue_dying(q)) if (nowait && !blk_queue_dying(q))
bio->bi_status = BLK_STS_AGAIN; bio->bi_status = BLK_STS_AGAIN;
@@ -1810,5 +1816,8 @@ int __init blk_dev_init(void)
if (bio_crypt_ctx_init() < 0) if (bio_crypt_ctx_init() < 0)
panic("Failed to allocate mem for bio crypt ctxs\n"); panic("Failed to allocate mem for bio crypt ctxs\n");
if (blk_crypto_init() < 0)
panic("Failed to init blk-crypto\n");
return 0; return 0;
} }

798
block/blk-crypto.c Normal file
View File

@@ -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;
}

7
include/linux/bio-crypt-ctx.h
View File

@@ -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) static inline bool bio_crypt_has_keyslot(struct bio *bio)
{ {
return bio->bi_crypt_context->keyslot >= 0; 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, unsigned int dun_bits,
gfp_t gfp_mask) { } 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 void bio_set_data_unit_num(struct bio *bio, u64 dun) { }
static inline bool bio_crypt_has_keyslot(struct bio *bio) static inline bool bio_crypt_has_keyslot(struct bio *bio)

62
include/linux/blk-crypto.h Normal file
View File

@@ -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 */