Update the device-mapper core to support exposing the inline crypto
support of the underlying device(s) through the device-mapper device.
This works by creating a "passthrough keyslot manager" for the dm
device, which declares support for encryption settings which all
underlying devices support. When a supported setting is used, the bio
cloning code handles cloning the crypto context to the bios for all the
underlying devices. When an unsupported setting is used, the blk-crypto
fallback is used as usual.
Crypto support on each underlying device is ignored unless the
corresponding dm target opts into exposing it. This is needed because
for inline crypto to semantically operate on the original bio, the data
must not be transformed by the dm target. Thus, targets like dm-linear
can expose crypto support of the underlying device, but targets like
dm-crypt can't. (dm-crypt could use inline crypto itself, though.)
When a key is evicted from the dm device, it is evicted from all
underlying devices.
A DM device's table can only be changed if the "new" inline encryption
capabilities are a superset of the "old" inline encryption capabilities.
Attempts to make changes to the table that result in some inline encryption
capability becoming no longer supported will be rejected.
Co-developed-by: Eric Biggers <[email protected]>
Signed-off-by: Eric Biggers <[email protected]>
Signed-off-by: Satya Tangirala <[email protected]>
---
block/blk-crypto.c | 1 +
block/keyslot-manager.c | 89 +++++++++++++
drivers/md/dm-ioctl.c | 8 ++
drivers/md/dm.c | 217 +++++++++++++++++++++++++++++++-
drivers/md/dm.h | 19 +++
include/linux/device-mapper.h | 6 +
include/linux/keyslot-manager.h | 17 +++
7 files changed, 356 insertions(+), 1 deletion(-)
diff --git a/block/blk-crypto.c b/block/blk-crypto.c
index 5da43f0973b4..c2be8f15006c 100644
--- a/block/blk-crypto.c
+++ b/block/blk-crypto.c
@@ -409,3 +409,4 @@ int blk_crypto_evict_key(struct request_queue *q,
*/
return blk_crypto_fallback_evict_key(key);
}
+EXPORT_SYMBOL_GPL(blk_crypto_evict_key);
diff --git a/block/keyslot-manager.c b/block/keyslot-manager.c
index 5ad476dafeab..e16e4a074765 100644
--- a/block/keyslot-manager.c
+++ b/block/keyslot-manager.c
@@ -416,6 +416,95 @@ void blk_ksm_unregister(struct request_queue *q)
{
q->ksm = NULL;
}
+EXPORT_SYMBOL_GPL(blk_ksm_unregister);
+
+/**
+ * blk_ksm_intersect_modes() - restrict supported modes by child device
+ * @parent: The keyslot manager for parent device
+ * @child: The keyslot manager for child device, or NULL
+ *
+ * Clear any crypto mode support bits in @parent that aren't set in @child.
+ * If @child is NULL, then all parent bits are cleared.
+ *
+ * Only use this when setting up the keyslot manager for a layered device,
+ * before it's been exposed yet.
+ */
+void blk_ksm_intersect_modes(struct blk_keyslot_manager *parent,
+ const struct blk_keyslot_manager *child)
+{
+ if (child) {
+ unsigned int i;
+
+ parent->max_dun_bytes_supported =
+ min(parent->max_dun_bytes_supported,
+ child->max_dun_bytes_supported);
+ for (i = 0; i < ARRAY_SIZE(child->crypto_modes_supported);
+ i++) {
+ parent->crypto_modes_supported[i] &=
+ child->crypto_modes_supported[i];
+ }
+ } else {
+ parent->max_dun_bytes_supported = 0;
+ memset(parent->crypto_modes_supported, 0,
+ sizeof(parent->crypto_modes_supported));
+ }
+}
+EXPORT_SYMBOL_GPL(blk_ksm_intersect_modes);
+
+/**
+ * blk_ksm_is_superset() - Check if a KSM supports a superset of crypto modes
+ * and DUN bytes that another KSM supports.
+ * @ksm_superset: The KSM that we want to verify is a superset
+ * @ksm_subset: The KSM that we want to verify is a subset
+ *
+ * Return: True if @ksm_superset supports a superset of the crypto modes and DUN
+ * bytes that @ksm_subset supports.
+ */
+bool blk_ksm_is_superset(struct blk_keyslot_manager *ksm_superset,
+ struct blk_keyslot_manager *ksm_subset)
+{
+ int i;
+
+ if (!ksm_subset)
+ return true;
+
+ if (!ksm_superset)
+ return false;
+
+ for (i = 0; i < ARRAY_SIZE(ksm_superset->crypto_modes_supported); i++) {
+ if (ksm_subset->crypto_modes_supported[i] &
+ (~ksm_superset->crypto_modes_supported[i])) {
+ return false;
+ }
+ }
+
+ if (ksm_subset->max_dun_bytes_supported >
+ ksm_superset->max_dun_bytes_supported) {
+ return false;
+ }
+
+ return true;
+}
+EXPORT_SYMBOL_GPL(blk_ksm_is_superset);
+
+/**
+ * blk_ksm_update_capabilities() - Update the restrictions of a KSM to those of
+ * another KSM
+ * @target_ksm: The KSM whose restrictions to update.
+ * @reference_ksm: The KSM to whose restrictions this function will update
+ * @target_ksm's restrictions to,
+ */
+void blk_ksm_update_capabilities(struct blk_keyslot_manager *target_ksm,
+ struct blk_keyslot_manager *reference_ksm)
+{
+ memcpy(target_ksm->crypto_modes_supported,
+ reference_ksm->crypto_modes_supported,
+ sizeof(target_ksm->crypto_modes_supported));
+
+ target_ksm->max_dun_bytes_supported =
+ reference_ksm->max_dun_bytes_supported;
+}
+EXPORT_SYMBOL_GPL(blk_ksm_update_capabilities);
/**
* blk_ksm_init_passthrough() - Init a passthrough keyslot manager
diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c
index cd0478d44058..2b3efa9f9fae 100644
--- a/drivers/md/dm-ioctl.c
+++ b/drivers/md/dm-ioctl.c
@@ -1358,6 +1358,10 @@ static int table_load(struct file *filp, struct dm_ioctl *param, size_t param_si
goto err_unlock_md_type;
}
+ r = dm_verify_inline_encryption(md, t);
+ if (r)
+ goto err_unlock_md_type;
+
if (dm_get_md_type(md) == DM_TYPE_NONE) {
/* Initial table load: acquire type of table. */
dm_set_md_type(md, dm_table_get_type(t));
@@ -2114,6 +2118,10 @@ int __init dm_early_create(struct dm_ioctl *dmi,
if (r)
goto err_destroy_table;
+ r = dm_verify_inline_encryption(md, t);
+ if (r)
+ goto err_destroy_table;
+
md->type = dm_table_get_type(t);
/* setup md->queue to reflect md's type (may block) */
r = dm_setup_md_queue(md, t);
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index c18fc2548518..22bb2c90583d 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -28,6 +28,7 @@
#include <linux/refcount.h>
#include <linux/part_stat.h>
#include <linux/blk-crypto.h>
+#include <linux/keyslot-manager.h>
#define DM_MSG_PREFIX "core"
@@ -1721,6 +1722,8 @@ static const struct dax_operations dm_dax_ops;
static void dm_wq_work(struct work_struct *work);
+static void dm_destroy_inline_encryption(struct mapped_device *md);
+
static void cleanup_mapped_device(struct mapped_device *md)
{
if (md->wq)
@@ -1742,8 +1745,10 @@ static void cleanup_mapped_device(struct mapped_device *md)
put_disk(md->disk);
}
- if (md->queue)
+ if (md->queue) {
+ dm_destroy_inline_encryption(md);
blk_cleanup_queue(md->queue);
+ }
cleanup_srcu_struct(&md->io_barrier);
@@ -1949,6 +1954,206 @@ static void event_callback(void *context)
dm_issue_global_event();
}
+#ifdef CONFIG_BLK_INLINE_ENCRYPTION
+
+struct dm_keyslot_evict_args {
+ const struct blk_crypto_key *key;
+ int err;
+};
+
+static int dm_keyslot_evict_callback(struct dm_target *ti, struct dm_dev *dev,
+ sector_t start, sector_t len, void *data)
+{
+ struct dm_keyslot_evict_args *args = data;
+ int err;
+
+ err = blk_crypto_evict_key(bdev_get_queue(dev->bdev), args->key);
+ if (!args->err)
+ args->err = err;
+ /* Always try to evict the key from all devices. */
+ return 0;
+}
+
+/*
+ * When an inline encryption key is evicted from a device-mapper device, evict
+ * it from all the underlying devices.
+ */
+static int dm_keyslot_evict(struct blk_keyslot_manager *ksm,
+ const struct blk_crypto_key *key, unsigned int slot)
+{
+ struct mapped_device *md = ksm->priv;
+ struct dm_keyslot_evict_args args = { key };
+ struct dm_table *t;
+ int srcu_idx;
+ int i;
+ struct dm_target *ti;
+
+ t = dm_get_live_table(md, &srcu_idx);
+ if (!t)
+ return 0;
+ for (i = 0; i < dm_table_get_num_targets(t); i++) {
+ ti = dm_table_get_target(t, i);
+ if (!ti->type->iterate_devices)
+ continue;
+ ti->type->iterate_devices(ti, dm_keyslot_evict_callback, &args);
+ }
+ dm_put_live_table(md, srcu_idx);
+ return args.err;
+}
+
+static struct blk_ksm_ll_ops dm_ksm_ll_ops = {
+ .keyslot_evict = dm_keyslot_evict,
+};
+
+static int device_intersect_crypto_modes(struct dm_target *ti,
+ struct dm_dev *dev, sector_t start,
+ sector_t len, void *data)
+{
+ struct blk_keyslot_manager *parent = data;
+ struct blk_keyslot_manager *child = bdev_get_queue(dev->bdev)->ksm;
+
+ blk_ksm_intersect_modes(parent, child);
+ return 0;
+}
+
+/*
+ * Constructs and returns a keyslot manager that represents the crypto
+ * capabilities of the devices described by the dm_table. However, if the
+ * constructed keyslot manager does not support a superset of the crypto
+ * capabilities supported by the currect keyslot manager of the mapped_device,
+ * it returns an error instead, since we don't support restricting crypto
+ * capabilities on table changes.
+ */
+static struct blk_keyslot_manager *
+dm_init_inline_encryption(struct mapped_device *md, struct dm_table *t)
+{
+ struct blk_keyslot_manager *ksm;
+ struct dm_target *ti;
+ unsigned int i;
+
+ ksm = kmalloc(sizeof(*ksm), GFP_KERNEL);
+ if (!ksm)
+ return ERR_PTR(-EINVAL);
+ blk_ksm_init_passthrough(ksm);
+ ksm->ksm_ll_ops = dm_ksm_ll_ops;
+ ksm->max_dun_bytes_supported = UINT_MAX;
+ memset(ksm->crypto_modes_supported, 0xFF,
+ sizeof(ksm->crypto_modes_supported));
+ ksm->priv = md;
+
+ for (i = 0; i < dm_table_get_num_targets(t); i++) {
+ ti = dm_table_get_target(t, i);
+
+ if (!ti->may_passthrough_inline_crypto) {
+ blk_ksm_intersect_modes(ksm, NULL);
+ break;
+ }
+ if (!ti->type->iterate_devices)
+ continue;
+ ti->type->iterate_devices(ti, device_intersect_crypto_modes,
+ ksm);
+ }
+
+ if (!blk_ksm_is_superset(ksm, md->queue->ksm)) {
+ DMWARN("Inline encryption capabilities of new DM table were more restrictive than the old table's. This is not supported!");
+ blk_ksm_destroy(ksm);
+ return ERR_PTR(-EOPNOTSUPP);
+ }
+
+ return ksm;
+}
+
+/**
+ * dm_verify_inline_encryption() - Verifies that the current keyslot manager of
+ * the mapped_device can be replaced by the
+ * keyslot manager of a given dm_table.
+ * @md: The mapped_device
+ * @t: The dm_table
+ *
+ * In particular, this function checks that the keyslot manager that will be
+ * constructed for the dm_table will support a superset of the capabilities that
+ * the current keyslot manager of the mapped_device supports.
+ *
+ * Return: 0 if the table's keyslot_manager can replace the current keyslot
+ * manager of the mapped_device. Negative value otherwise.
+ */
+int dm_verify_inline_encryption(struct mapped_device *md, struct dm_table *t)
+{
+ struct blk_keyslot_manager *ksm = dm_init_inline_encryption(md, t);
+
+ if (IS_ERR(ksm))
+ return PTR_ERR(ksm);
+ blk_ksm_destroy(ksm);
+
+ return 0;
+}
+
+static void dm_update_keyslot_manager(struct mapped_device *md,
+ struct blk_keyslot_manager *ksm)
+{
+ bool ksm_is_empty = true;
+ int i;
+
+ /*
+ * If the new KSM doesn't actually support any crypto modes, we may as
+ * well set a NULL ksm.
+ */
+ ksm_is_empty = true;
+ for (i = 0; i < ARRAY_SIZE(ksm->crypto_modes_supported); i++) {
+ if (ksm->crypto_modes_supported[i]) {
+ ksm_is_empty = false;
+ break;
+ }
+ }
+
+ if (ksm_is_empty) {
+ blk_ksm_destroy(ksm);
+
+ /* At this point, md->queue->ksm must also be NULL, since we're
+ * guaranteed that ksm is a superset of md->queue->ksm, and we
+ * never set md->queue->ksm to a non-null empty ksm.
+ */
+ if (WARN_ON(md->queue->ksm))
+ blk_ksm_register(NULL, md->queue);
+ return;
+ }
+
+ /* Make the ksm less restrictive */
+ if (!md->queue->ksm) {
+ blk_ksm_register(ksm, md->queue);
+ } else {
+ blk_ksm_update_capabilities(md->queue->ksm, ksm);
+ blk_ksm_destroy(ksm);
+ }
+}
+
+static void dm_destroy_inline_encryption(struct mapped_device *md)
+{
+ if (!md->queue->ksm)
+ return;
+ blk_ksm_destroy(md->queue->ksm);
+ blk_ksm_unregister(md->queue);
+}
+
+#else /* CONFIG_BLK_INLINE_ENCRYPTION */
+
+static inline struct blk_keyslot_manager *
+dm_init_inline_encryption(struct mapped_device *md, struct dm_table *t)
+{
+ return NULL;
+}
+
+static void dm_update_keyslot_manager(struct mapped_device *md,
+ struct blk_keyslot_manager *ksm)
+{
+}
+
+static inline void dm_destroy_inline_encryption(struct mapped_device *md)
+{
+}
+
+#endif /* !CONFIG_BLK_INLINE_ENCRYPTION */
+
/*
* Returns old map, which caller must destroy.
*/
@@ -1959,6 +2164,7 @@ static struct dm_table *__bind(struct mapped_device *md, struct dm_table *t,
struct request_queue *q = md->queue;
bool request_based = dm_table_request_based(t);
sector_t size;
+ struct blk_keyslot_manager *ksm;
int ret;
lockdep_assert_held(&md->suspend_lock);
@@ -1994,12 +2200,21 @@ static struct dm_table *__bind(struct mapped_device *md, struct dm_table *t,
md->immutable_target = dm_table_get_immutable_target(t);
}
+ ksm = dm_init_inline_encryption(md, t);
+ if (IS_ERR(ksm)) {
+ old_map = ERR_PTR(PTR_ERR(ksm));
+ goto out;
+ }
+
ret = __bind_mempools(md, t);
if (ret) {
+ blk_ksm_destroy(ksm);
old_map = ERR_PTR(ret);
goto out;
}
+ dm_update_keyslot_manager(md, ksm);
+
old_map = rcu_dereference_protected(md->map, lockdep_is_held(&md->suspend_lock));
rcu_assign_pointer(md->map, (void *)t);
md->immutable_target_type = dm_table_get_immutable_target_type(t);
diff --git a/drivers/md/dm.h b/drivers/md/dm.h
index fffe1e289c53..eaf92e4cbe70 100644
--- a/drivers/md/dm.h
+++ b/drivers/md/dm.h
@@ -208,4 +208,23 @@ void dm_free_md_mempools(struct dm_md_mempools *pools);
*/
unsigned dm_get_reserved_bio_based_ios(void);
+/*
+ * Inline Encryption
+ */
+struct blk_keyslot_manager;
+
+#ifdef CONFIG_BLK_INLINE_ENCRYPTION
+
+int dm_verify_inline_encryption(struct mapped_device *md, struct dm_table *t);
+
+#else /* !CONFIG_BLK_INLINE_ENCRYPTION */
+
+static inline int dm_verify_inline_encryption(struct mapped_device *md,
+ struct dm_table *t)
+{
+ return 0;
+}
+
+#endif /* !CONFIG_BLK_INLINE_ENCRYPTION */
+
#endif
diff --git a/include/linux/device-mapper.h b/include/linux/device-mapper.h
index 61a66fb8ebb3..6d05a6a8a129 100644
--- a/include/linux/device-mapper.h
+++ b/include/linux/device-mapper.h
@@ -325,6 +325,12 @@ struct dm_target {
* whether or not its underlying devices have support.
*/
bool discards_supported:1;
+
+ /*
+ * Set if inline crypto capabilities from this target's underlying
+ * device(s) can be exposed via the device-mapper device.
+ */
+ bool may_passthrough_inline_crypto:1;
};
void *dm_per_bio_data(struct bio *bio, size_t data_size);
diff --git a/include/linux/keyslot-manager.h b/include/linux/keyslot-manager.h
index 37f1022b256f..4047f8cec01a 100644
--- a/include/linux/keyslot-manager.h
+++ b/include/linux/keyslot-manager.h
@@ -11,6 +11,8 @@
struct blk_keyslot_manager;
+#ifdef CONFIG_BLK_INLINE_ENCRYPTION
+
/**
* struct blk_ksm_ll_ops - functions to manage keyslots in hardware
* @keyslot_program: Program the specified key into the specified slot in the
@@ -106,6 +108,21 @@ void blk_ksm_reprogram_all_keys(struct blk_keyslot_manager *ksm);
void blk_ksm_destroy(struct blk_keyslot_manager *ksm);
+void blk_ksm_intersect_modes(struct blk_keyslot_manager *parent,
+ const struct blk_keyslot_manager *child);
+
void blk_ksm_init_passthrough(struct blk_keyslot_manager *ksm);
+bool blk_ksm_is_superset(struct blk_keyslot_manager *ksm_superset,
+ struct blk_keyslot_manager *ksm_subset);
+
+void blk_ksm_update_capabilities(struct blk_keyslot_manager *target_ksm,
+ struct blk_keyslot_manager *reference_ksm);
+
+#else /* CONFIG_BLK_INLINE_ENCRYPTION */
+
+static inline void blk_ksm_destroy(struct blk_keyslot_manager *ksm) { }
+
+#endif /* CONFIG_BLK_INLINE_ENCRYPTION */
+
#endif /* __LINUX_KEYSLOT_MANAGER_H */
--
2.29.0.rc1.297.gfa9743e501-goog
From: kernel test robot <[email protected]>
drivers/md/dm.c:2204:12-19: WARNING: ERR_CAST can be used with ksm
Use ERR_CAST inlined function instead of ERR_PTR(PTR_ERR(...))
Generated by: scripts/coccinelle/api/err_cast.cocci
CC: Satya Tangirala <[email protected]>
Signed-off-by: kernel test robot <[email protected]>
---
url: https://github.com/0day-ci/linux/commits/Satya-Tangirala/add-support-for-inline-encryption-to-device-mapper/20201016-054900
base: https://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm.git for-next
dm.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -2201,7 +2201,7 @@ static struct dm_table *__bind(struct ma
ksm = dm_init_inline_encryption(md, t);
if (IS_ERR(ksm)) {
- old_map = ERR_PTR(PTR_ERR(ksm));
+ old_map = ERR_CAST(ksm);
goto out;
}
Hi Satya,
Thank you for the patch! Perhaps something to improve:
[auto build test WARNING on dm/for-next]
[also build test WARNING on block/for-next linus/master linux/master v5.9 next-20201023]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]
url: https://github.com/0day-ci/linux/commits/Satya-Tangirala/add-support-for-inline-encryption-to-device-mapper/20201016-054900
base: https://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm.git for-next
config: i386-randconfig-c001-20201025 (attached as .config)
compiler: gcc-9 (Debian 9.3.0-15) 9.3.0
If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <[email protected]>
"coccinelle warnings: (new ones prefixed by >>)"
>> drivers/md/dm.c:2204:12-19: WARNING: ERR_CAST can be used with ksm
Please review and possibly fold the followup patch.
---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/[email protected]
On Thu, Oct 15, 2020 at 09:46:31PM +0000, Satya Tangirala wrote:
> Update the device-mapper core to support exposing the inline crypto
> support of the underlying device(s) through the device-mapper device.
>
> This works by creating a "passthrough keyslot manager" for the dm
> device, which declares support for encryption settings which all
> underlying devices support. When a supported setting is used, the bio
> cloning code handles cloning the crypto context to the bios for all the
> underlying devices. When an unsupported setting is used, the blk-crypto
> fallback is used as usual.
>
> Crypto support on each underlying device is ignored unless the
> corresponding dm target opts into exposing it. This is needed because
> for inline crypto to semantically operate on the original bio, the data
> must not be transformed by the dm target. Thus, targets like dm-linear
> can expose crypto support of the underlying device, but targets like
> dm-crypt can't. (dm-crypt could use inline crypto itself, though.)
>
> When a key is evicted from the dm device, it is evicted from all
> underlying devices.
>
> A DM device's table can only be changed if the "new" inline encryption
> capabilities are a superset of the "old" inline encryption capabilities.
> Attempts to make changes to the table that result in some inline encryption
> capability becoming no longer supported will be rejected.
>
> Co-developed-by: Eric Biggers <[email protected]>
> Signed-off-by: Eric Biggers <[email protected]>
> Signed-off-by: Satya Tangirala <[email protected]>
> ---
> block/blk-crypto.c | 1 +
> block/keyslot-manager.c | 89 +++++++++++++
> drivers/md/dm-ioctl.c | 8 ++
> drivers/md/dm.c | 217 +++++++++++++++++++++++++++++++-
> drivers/md/dm.h | 19 +++
> include/linux/device-mapper.h | 6 +
> include/linux/keyslot-manager.h | 17 +++
> 7 files changed, 356 insertions(+), 1 deletion(-)
I'm having a hard time understanding what's going on in this patch now. Besides
the simplifications I'm suggesting in other comments below, you should consider
splitting this into more than one patch. The block layer changes could be a
separate patch, as could the key eviction support.
>
> diff --git a/block/blk-crypto.c b/block/blk-crypto.c
> index 5da43f0973b4..c2be8f15006c 100644
> --- a/block/blk-crypto.c
> +++ b/block/blk-crypto.c
> @@ -409,3 +409,4 @@ int blk_crypto_evict_key(struct request_queue *q,
> */
> return blk_crypto_fallback_evict_key(key);
> }
> +EXPORT_SYMBOL_GPL(blk_crypto_evict_key);
> diff --git a/block/keyslot-manager.c b/block/keyslot-manager.c
> index 5ad476dafeab..e16e4a074765 100644
> --- a/block/keyslot-manager.c
> +++ b/block/keyslot-manager.c
> @@ -416,6 +416,95 @@ void blk_ksm_unregister(struct request_queue *q)
> {
> q->ksm = NULL;
> }
> +EXPORT_SYMBOL_GPL(blk_ksm_unregister);
blk_ksm_unregister() doesn't seem to be necessary, since it just sets a pointer
to NULL, which the callers could easily do themselves.
> +/**
> + * blk_ksm_intersect_modes() - restrict supported modes by child device
> + * @parent: The keyslot manager for parent device
> + * @child: The keyslot manager for child device, or NULL
> + *
> + * Clear any crypto mode support bits in @parent that aren't set in @child.
> + * If @child is NULL, then all parent bits are cleared.
> + *
> + * Only use this when setting up the keyslot manager for a layered device,
> + * before it's been exposed yet.
> + */
> +void blk_ksm_intersect_modes(struct blk_keyslot_manager *parent,
> + const struct blk_keyslot_manager *child)
> +{
> + if (child) {
> + unsigned int i;
> +
> + parent->max_dun_bytes_supported =
> + min(parent->max_dun_bytes_supported,
> + child->max_dun_bytes_supported);
> + for (i = 0; i < ARRAY_SIZE(child->crypto_modes_supported);
> + i++) {
> + parent->crypto_modes_supported[i] &=
> + child->crypto_modes_supported[i];
> + }
> + } else {
> + parent->max_dun_bytes_supported = 0;
> + memset(parent->crypto_modes_supported, 0,
> + sizeof(parent->crypto_modes_supported));
> + }
> +}
> +EXPORT_SYMBOL_GPL(blk_ksm_intersect_modes);
> +
> +/**
> + * blk_ksm_is_superset() - Check if a KSM supports a superset of crypto modes
> + * and DUN bytes that another KSM supports.
> + * @ksm_superset: The KSM that we want to verify is a superset
> + * @ksm_subset: The KSM that we want to verify is a subset
> + *
> + * Return: True if @ksm_superset supports a superset of the crypto modes and DUN
> + * bytes that @ksm_subset supports.
> + */
> +bool blk_ksm_is_superset(struct blk_keyslot_manager *ksm_superset,
> + struct blk_keyslot_manager *ksm_subset)
blk_ksm_is_superset() is confusing because it actually does "superset or the
same", not just "superset". That *is* the mathematical definition of superset,
but it may not be what people expect when they read this... Is there a better
name, or can the comment properly explain it?
> +/**
> + * blk_ksm_update_capabilities() - Update the restrictions of a KSM to those of
> + * another KSM
> + * @target_ksm: The KSM whose restrictions to update.
> + * @reference_ksm: The KSM to whose restrictions this function will update
> + * @target_ksm's restrictions to,
> + */
> +void blk_ksm_update_capabilities(struct blk_keyslot_manager *target_ksm,
> + struct blk_keyslot_manager *reference_ksm)
> +{
> + memcpy(target_ksm->crypto_modes_supported,
> + reference_ksm->crypto_modes_supported,
> + sizeof(target_ksm->crypto_modes_supported));
> +
> + target_ksm->max_dun_bytes_supported =
> + reference_ksm->max_dun_bytes_supported;
> +}
> +EXPORT_SYMBOL_GPL(blk_ksm_update_capabilities);
Wouldn't it be easier to replace the original blk_keyslot_manager, rather than
modify it? Then blk_ksm_update_capabilities() wouldn't be needed.
> diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c
> index cd0478d44058..2b3efa9f9fae 100644
> --- a/drivers/md/dm-ioctl.c
> +++ b/drivers/md/dm-ioctl.c
> @@ -1358,6 +1358,10 @@ static int table_load(struct file *filp, struct dm_ioctl *param, size_t param_si
> goto err_unlock_md_type;
> }
>
> + r = dm_verify_inline_encryption(md, t);
> + if (r)
> + goto err_unlock_md_type;
> +
> if (dm_get_md_type(md) == DM_TYPE_NONE) {
> /* Initial table load: acquire type of table. */
> dm_set_md_type(md, dm_table_get_type(t));
> @@ -2114,6 +2118,10 @@ int __init dm_early_create(struct dm_ioctl *dmi,
> if (r)
> goto err_destroy_table;
>
> + r = dm_verify_inline_encryption(md, t);
> + if (r)
> + goto err_destroy_table;
> +
> md->type = dm_table_get_type(t);
> /* setup md->queue to reflect md's type (may block) */
> r = dm_setup_md_queue(md, t);
Both table_load() and dm_early_create() call dm_setup_md_queue(). Wouldn't it
be simpler to handle inline encryption in dm_setup_md_queue(), instead of doing
it in both table_load() and dm_early_create()?
> +/*
> + * Constructs and returns a keyslot manager that represents the crypto
> + * capabilities of the devices described by the dm_table. However, if the
> + * constructed keyslot manager does not support a superset of the crypto
> + * capabilities supported by the currect keyslot manager of the mapped_device,
> + * it returns an error instead, since we don't support restricting crypto
> + * capabilities on table changes.
> + */
> +static struct blk_keyslot_manager *
> +dm_init_inline_encryption(struct mapped_device *md, struct dm_table *t)
> +{
> + struct blk_keyslot_manager *ksm;
> + struct dm_target *ti;
> + unsigned int i;
> +
> + ksm = kmalloc(sizeof(*ksm), GFP_KERNEL);
> + if (!ksm)
> + return ERR_PTR(-EINVAL);
ENOMEM, not EINVAL.
> + blk_ksm_init_passthrough(ksm);
> + ksm->ksm_ll_ops = dm_ksm_ll_ops;
> + ksm->max_dun_bytes_supported = UINT_MAX;
> + memset(ksm->crypto_modes_supported, 0xFF,
> + sizeof(ksm->crypto_modes_supported));
> + ksm->priv = md;
> +
> + for (i = 0; i < dm_table_get_num_targets(t); i++) {
> + ti = dm_table_get_target(t, i);
> +
> + if (!ti->may_passthrough_inline_crypto) {
> + blk_ksm_intersect_modes(ksm, NULL);
> + break;
> + }
> + if (!ti->type->iterate_devices)
> + continue;
> + ti->type->iterate_devices(ti, device_intersect_crypto_modes,
> + ksm);
> + }
> +
> + if (!blk_ksm_is_superset(ksm, md->queue->ksm)) {
> + DMWARN("Inline encryption capabilities of new DM table were more restrictive than the old table's. This is not supported!");
> + blk_ksm_destroy(ksm);
> + return ERR_PTR(-EOPNOTSUPP);
Missing kfree(ksm).
Also it looks like other code is using EINVAL for a bad dm table.
> + }
> +
> + return ksm;
How about returning NULL if no crypto modes are actually supported?
> +/**
> + * dm_verify_inline_encryption() - Verifies that the current keyslot manager of
> + * the mapped_device can be replaced by the
> + * keyslot manager of a given dm_table.
> + * @md: The mapped_device
> + * @t: The dm_table
> + *
> + * In particular, this function checks that the keyslot manager that will be
> + * constructed for the dm_table will support a superset of the capabilities that
> + * the current keyslot manager of the mapped_device supports.
> + *
> + * Return: 0 if the table's keyslot_manager can replace the current keyslot
> + * manager of the mapped_device. Negative value otherwise.
> + */
> +int dm_verify_inline_encryption(struct mapped_device *md, struct dm_table *t)
> +{
> + struct blk_keyslot_manager *ksm = dm_init_inline_encryption(md, t);
> +
> + if (IS_ERR(ksm))
> + return PTR_ERR(ksm);
> + blk_ksm_destroy(ksm);
> +
> + return 0;
> +}
This function seems redundant with dm_init_inline_encryption(). Wouldn't it be
simpler to do:
- dm_setup_md_queue() and dm_swap_table() call dm_init_inline_encryption() after
dm_calculate_queue_limits().
- ksm gets passed to dm_table_set_restrictions(), which calls
dm_update_keyslot_manager() (maybe rename to dm_update_inline_encryption()?)
to actually set q->ksm.
That way, the crypto capabilities would be handled similarly to how the
queue_limits are already handled.
> +static void dm_update_keyslot_manager(struct mapped_device *md,
> + struct blk_keyslot_manager *ksm)
> +{
> + bool ksm_is_empty = true;
> + int i;
> +
> + /*
> + * If the new KSM doesn't actually support any crypto modes, we may as
> + * well set a NULL ksm.
> + */
> + ksm_is_empty = true;
> + for (i = 0; i < ARRAY_SIZE(ksm->crypto_modes_supported); i++) {
> + if (ksm->crypto_modes_supported[i]) {
> + ksm_is_empty = false;
> + break;
> + }
> + }
dm_init_inline_encryption() seems like a better place for this "are no modes
supported" logic.
> + if (ksm_is_empty) {
> + blk_ksm_destroy(ksm);
> +
> + /* At this point, md->queue->ksm must also be NULL, since we're
> + * guaranteed that ksm is a superset of md->queue->ksm, and we
> + * never set md->queue->ksm to a non-null empty ksm.
> + */
> + if (WARN_ON(md->queue->ksm))
> + blk_ksm_register(NULL, md->queue);
> + return;
> + }
> +
> + /* Make the ksm less restrictive */
> + if (!md->queue->ksm) {
> + blk_ksm_register(ksm, md->queue);
> + } else {
> + blk_ksm_update_capabilities(md->queue->ksm, ksm);
> + blk_ksm_destroy(ksm);
> + }
> +}
Wouldn't it be simpler to just destroy (and free) the existing
blk_keyslot_manager (if any), then set the new one (if it's not NULL)?
> +static void dm_destroy_inline_encryption(struct mapped_device *md)
> +{
> + if (!md->queue->ksm)
> + return;
> + blk_ksm_destroy(md->queue->ksm);
Missing kfree().
> + blk_ksm_unregister(md->queue);
> +}
> +
> +#else /* CONFIG_BLK_INLINE_ENCRYPTION */
> +
> +static inline struct blk_keyslot_manager *
> +dm_init_inline_encryption(struct mapped_device *md, struct dm_table *t)
> +{
> + return NULL;
> +}
Seems it would be simpler for these functions to take a request_queue instead of
a mapped_device.
> /*
> * Returns old map, which caller must destroy.
> */
> @@ -1959,6 +2164,7 @@ static struct dm_table *__bind(struct mapped_device *md, struct dm_table *t,
> struct request_queue *q = md->queue;
> bool request_based = dm_table_request_based(t);
> sector_t size;
> + struct blk_keyslot_manager *ksm;
> int ret;
>
> lockdep_assert_held(&md->suspend_lock);
> @@ -1994,12 +2200,21 @@ static struct dm_table *__bind(struct mapped_device *md, struct dm_table *t,
> md->immutable_target = dm_table_get_immutable_target(t);
> }
>
> + ksm = dm_init_inline_encryption(md, t);
> + if (IS_ERR(ksm)) {
> + old_map = ERR_PTR(PTR_ERR(ksm));
> + goto out;
> + }
It seems too late to fail here, since the mapped_device already started being
updated. What I suggested above would address this.
> +#ifdef CONFIG_BLK_INLINE_ENCRYPTION
> +
> /**
> * struct blk_ksm_ll_ops - functions to manage keyslots in hardware
> * @keyslot_program: Program the specified key into the specified slot in the
> @@ -106,6 +108,21 @@ void blk_ksm_reprogram_all_keys(struct blk_keyslot_manager *ksm);
>
> void blk_ksm_destroy(struct blk_keyslot_manager *ksm);
>
> +void blk_ksm_intersect_modes(struct blk_keyslot_manager *parent,
> + const struct blk_keyslot_manager *child);
> +
> void blk_ksm_init_passthrough(struct blk_keyslot_manager *ksm);
>
> +bool blk_ksm_is_superset(struct blk_keyslot_manager *ksm_superset,
> + struct blk_keyslot_manager *ksm_subset);
> +
> +void blk_ksm_update_capabilities(struct blk_keyslot_manager *target_ksm,
> + struct blk_keyslot_manager *reference_ksm);
> +
> +#else /* CONFIG_BLK_INLINE_ENCRYPTION */
> +
> +static inline void blk_ksm_destroy(struct blk_keyslot_manager *ksm) { }
> +
> +#endif /* CONFIG_BLK_INLINE_ENCRYPTION */
Is the blk_ksm_destroy() stub really needed?
- Eric
On Tue, Oct 27, 2020 at 02:31:51PM -0700, Eric Biggers wrote:
> On Thu, Oct 15, 2020 at 09:46:31PM +0000, Satya Tangirala wrote:
> > Update the device-mapper core to support exposing the inline crypto
> > support of the underlying device(s) through the device-mapper device.
> >
> > This works by creating a "passthrough keyslot manager" for the dm
> > device, which declares support for encryption settings which all
> > underlying devices support. When a supported setting is used, the bio
> > cloning code handles cloning the crypto context to the bios for all the
> > underlying devices. When an unsupported setting is used, the blk-crypto
> > fallback is used as usual.
> >
> > Crypto support on each underlying device is ignored unless the
> > corresponding dm target opts into exposing it. This is needed because
> > for inline crypto to semantically operate on the original bio, the data
> > must not be transformed by the dm target. Thus, targets like dm-linear
> > can expose crypto support of the underlying device, but targets like
> > dm-crypt can't. (dm-crypt could use inline crypto itself, though.)
> >
> > When a key is evicted from the dm device, it is evicted from all
> > underlying devices.
> >
> > A DM device's table can only be changed if the "new" inline encryption
> > capabilities are a superset of the "old" inline encryption capabilities.
> > Attempts to make changes to the table that result in some inline encryption
> > capability becoming no longer supported will be rejected.
> >
> > Co-developed-by: Eric Biggers <[email protected]>
> > Signed-off-by: Eric Biggers <[email protected]>
> > Signed-off-by: Satya Tangirala <[email protected]>
> > ---
> > block/blk-crypto.c | 1 +
> > block/keyslot-manager.c | 89 +++++++++++++
> > drivers/md/dm-ioctl.c | 8 ++
> > drivers/md/dm.c | 217 +++++++++++++++++++++++++++++++-
> > drivers/md/dm.h | 19 +++
> > include/linux/device-mapper.h | 6 +
> > include/linux/keyslot-manager.h | 17 +++
> > 7 files changed, 356 insertions(+), 1 deletion(-)
>
> I'm having a hard time understanding what's going on in this patch now. Besides
> the simplifications I'm suggesting in other comments below, you should consider
> splitting this into more than one patch. The block layer changes could be a
> separate patch, as could the key eviction support.
>
Sure - I'll also add more details on the patch in the commit message.
> >
> > diff --git a/block/blk-crypto.c b/block/blk-crypto.c
> > index 5da43f0973b4..c2be8f15006c 100644
> > --- a/block/blk-crypto.c
> > +++ b/block/blk-crypto.c
> > @@ -409,3 +409,4 @@ int blk_crypto_evict_key(struct request_queue *q,
> > */
> > return blk_crypto_fallback_evict_key(key);
> > }
> > +EXPORT_SYMBOL_GPL(blk_crypto_evict_key);
> > diff --git a/block/keyslot-manager.c b/block/keyslot-manager.c
> > index 5ad476dafeab..e16e4a074765 100644
> > --- a/block/keyslot-manager.c
> > +++ b/block/keyslot-manager.c
> > @@ -416,6 +416,95 @@ void blk_ksm_unregister(struct request_queue *q)
> > {
> > q->ksm = NULL;
> > }
> > +EXPORT_SYMBOL_GPL(blk_ksm_unregister);
>
> blk_ksm_unregister() doesn't seem to be necessary, since it just sets a pointer
> to NULL, which the callers could easily do themselves.
>
> > +/**
> > + * blk_ksm_intersect_modes() - restrict supported modes by child device
> > + * @parent: The keyslot manager for parent device
> > + * @child: The keyslot manager for child device, or NULL
> > + *
> > + * Clear any crypto mode support bits in @parent that aren't set in @child.
> > + * If @child is NULL, then all parent bits are cleared.
> > + *
> > + * Only use this when setting up the keyslot manager for a layered device,
> > + * before it's been exposed yet.
> > + */
> > +void blk_ksm_intersect_modes(struct blk_keyslot_manager *parent,
> > + const struct blk_keyslot_manager *child)
> > +{
> > + if (child) {
> > + unsigned int i;
> > +
> > + parent->max_dun_bytes_supported =
> > + min(parent->max_dun_bytes_supported,
> > + child->max_dun_bytes_supported);
> > + for (i = 0; i < ARRAY_SIZE(child->crypto_modes_supported);
> > + i++) {
> > + parent->crypto_modes_supported[i] &=
> > + child->crypto_modes_supported[i];
> > + }
> > + } else {
> > + parent->max_dun_bytes_supported = 0;
> > + memset(parent->crypto_modes_supported, 0,
> > + sizeof(parent->crypto_modes_supported));
> > + }
> > +}
> > +EXPORT_SYMBOL_GPL(blk_ksm_intersect_modes);
> > +
> > +/**
> > + * blk_ksm_is_superset() - Check if a KSM supports a superset of crypto modes
> > + * and DUN bytes that another KSM supports.
> > + * @ksm_superset: The KSM that we want to verify is a superset
> > + * @ksm_subset: The KSM that we want to verify is a subset
> > + *
> > + * Return: True if @ksm_superset supports a superset of the crypto modes and DUN
> > + * bytes that @ksm_subset supports.
> > + */
> > +bool blk_ksm_is_superset(struct blk_keyslot_manager *ksm_superset,
> > + struct blk_keyslot_manager *ksm_subset)
>
> blk_ksm_is_superset() is confusing because it actually does "superset or the
> same", not just "superset". That *is* the mathematical definition of superset,
> but it may not be what people expect when they read this... Is there a better
> name, or can the comment properly explain it?
>
A better name still eludes me, but I'll definitely at least comment it better
if I still can't think of a better name.
> > +/**
> > + * blk_ksm_update_capabilities() - Update the restrictions of a KSM to those of
> > + * another KSM
> > + * @target_ksm: The KSM whose restrictions to update.
> > + * @reference_ksm: The KSM to whose restrictions this function will update
> > + * @target_ksm's restrictions to,
> > + */
> > +void blk_ksm_update_capabilities(struct blk_keyslot_manager *target_ksm,
> > + struct blk_keyslot_manager *reference_ksm)
> > +{
> > + memcpy(target_ksm->crypto_modes_supported,
> > + reference_ksm->crypto_modes_supported,
> > + sizeof(target_ksm->crypto_modes_supported));
> > +
> > + target_ksm->max_dun_bytes_supported =
> > + reference_ksm->max_dun_bytes_supported;
> > +}
> > +EXPORT_SYMBOL_GPL(blk_ksm_update_capabilities);
>
> Wouldn't it be easier to replace the original blk_keyslot_manager, rather than
> modify it? Then blk_ksm_update_capabilities() wouldn't be needed.
>
I didn't want to replace the original blk_keyslot_manager because it's
possible that e.g. fscrypt is checking for crypto capabilities support
via blk_ksm_crypto_cfg_supported() when DM wants to replace the
blk_keyslot_manager. DM would have to free the memory used by the
blk_keyslot_manager, but blk_ksm_crypto_cfg_supported() might still
be trying to access that memory. I did it this way to avoid having to
add refcounts or something else to the blk_keyslot_manager...(And I
didn't bother adding any synchronization code since the capabilities
only ever expand, and never contract).
> > diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c
> > index cd0478d44058..2b3efa9f9fae 100644
> > --- a/drivers/md/dm-ioctl.c
> > +++ b/drivers/md/dm-ioctl.c
> > @@ -1358,6 +1358,10 @@ static int table_load(struct file *filp, struct dm_ioctl *param, size_t param_si
> > goto err_unlock_md_type;
> > }
> >
> > + r = dm_verify_inline_encryption(md, t);
> > + if (r)
> > + goto err_unlock_md_type;
> > +
> > if (dm_get_md_type(md) == DM_TYPE_NONE) {
> > /* Initial table load: acquire type of table. */
> > dm_set_md_type(md, dm_table_get_type(t));
> > @@ -2114,6 +2118,10 @@ int __init dm_early_create(struct dm_ioctl *dmi,
> > if (r)
> > goto err_destroy_table;
> >
> > + r = dm_verify_inline_encryption(md, t);
> > + if (r)
> > + goto err_destroy_table;
> > +
> > md->type = dm_table_get_type(t);
> > /* setup md->queue to reflect md's type (may block) */
> > r = dm_setup_md_queue(md, t);
>
> Both table_load() and dm_early_create() call dm_setup_md_queue(). Wouldn't it
> be simpler to handle inline encryption in dm_setup_md_queue(), instead of doing
> it in both table_load() and dm_early_create()?
>
table_load() only calls dm_setup_md_queue() on initial table load (when
the md_type is DM_TYPE_NONE), so I can't call
dm_verify_inline_encryption() in only dm_setup_md_queue(), because
dm_verify_inline_encryption() needs to run on every table load.
> > +/*
> > + * Constructs and returns a keyslot manager that represents the crypto
> > + * capabilities of the devices described by the dm_table. However, if the
> > + * constructed keyslot manager does not support a superset of the crypto
> > + * capabilities supported by the currect keyslot manager of the mapped_device,
> > + * it returns an error instead, since we don't support restricting crypto
> > + * capabilities on table changes.
> > + */
> > +static struct blk_keyslot_manager *
> > +dm_init_inline_encryption(struct mapped_device *md, struct dm_table *t)
> > +{
> > + struct blk_keyslot_manager *ksm;
> > + struct dm_target *ti;
> > + unsigned int i;
> > +
> > + ksm = kmalloc(sizeof(*ksm), GFP_KERNEL);
> > + if (!ksm)
> > + return ERR_PTR(-EINVAL);
>
> ENOMEM, not EINVAL.
>
Ahhh :(
> > + blk_ksm_init_passthrough(ksm);
> > + ksm->ksm_ll_ops = dm_ksm_ll_ops;
> > + ksm->max_dun_bytes_supported = UINT_MAX;
> > + memset(ksm->crypto_modes_supported, 0xFF,
> > + sizeof(ksm->crypto_modes_supported));
> > + ksm->priv = md;
> > +
> > + for (i = 0; i < dm_table_get_num_targets(t); i++) {
> > + ti = dm_table_get_target(t, i);
> > +
> > + if (!ti->may_passthrough_inline_crypto) {
> > + blk_ksm_intersect_modes(ksm, NULL);
> > + break;
> > + }
> > + if (!ti->type->iterate_devices)
> > + continue;
> > + ti->type->iterate_devices(ti, device_intersect_crypto_modes,
> > + ksm);
> > + }
> > +
> > + if (!blk_ksm_is_superset(ksm, md->queue->ksm)) {
> > + DMWARN("Inline encryption capabilities of new DM table were more restrictive than the old table's. This is not supported!");
> > + blk_ksm_destroy(ksm);
> > + return ERR_PTR(-EOPNOTSUPP);
>
> Missing kfree(ksm).
>
Ah I totally forgot blk_ksm_destroy() doesn't free the memory used by
the ksm (not anymore at least, I'm getting confused by the numerous
revisions that code went through) - I'll need to fix that everywhere.
> Also it looks like other code is using EINVAL for a bad dm table.
>
> > + }
> > +
> > + return ksm;
>
> How about returning NULL if no crypto modes are actually supported?
>
> > +/**
> > + * dm_verify_inline_encryption() - Verifies that the current keyslot manager of
> > + * the mapped_device can be replaced by the
> > + * keyslot manager of a given dm_table.
> > + * @md: The mapped_device
> > + * @t: The dm_table
> > + *
> > + * In particular, this function checks that the keyslot manager that will be
> > + * constructed for the dm_table will support a superset of the capabilities that
> > + * the current keyslot manager of the mapped_device supports.
> > + *
> > + * Return: 0 if the table's keyslot_manager can replace the current keyslot
> > + * manager of the mapped_device. Negative value otherwise.
> > + */
> > +int dm_verify_inline_encryption(struct mapped_device *md, struct dm_table *t)
> > +{
> > + struct blk_keyslot_manager *ksm = dm_init_inline_encryption(md, t);
> > +
> > + if (IS_ERR(ksm))
> > + return PTR_ERR(ksm);
> > + blk_ksm_destroy(ksm);
> > +
> > + return 0;
> > +}
>
> This function seems redundant with dm_init_inline_encryption(). Wouldn't it be
> simpler to do:
>
> - dm_setup_md_queue() and dm_swap_table() call dm_init_inline_encryption() after
> dm_calculate_queue_limits().
>
> - ksm gets passed to dm_table_set_restrictions(), which calls
> dm_update_keyslot_manager() (maybe rename to dm_update_inline_encryption()?)
> to actually set q->ksm.
>
> That way, the crypto capabilities would be handled similarly to how the
> queue_limits are already handled.
>
If we call it from dm_swap_table(), we could have it pass the returned
ksm to __bind(), either as a new argument, or by adding the ksm to the
queue_limits (I'll have to check if that's ok/a good idea in the first
place), and __bind() could send the argument to
dm_table_set_restrictions()
But the real issue is, I think we should check whether a new table is
valid (from the ksm capabilities support perspective) at the time that
table is loaded (as opposed to only checking it when DM attempts to swap
it in, which might be a lot later, when the user resumes the device) - so
I can't only call it from dm_setup_md_queue(), and I'd have to call it
from table_load() anyway. And the returned ksm that table_load() obtains
from dm_init_inline_encryption() can't really be used - because
1) the ksm constructed at dm_swap_table() might actually support more
capabilities than the ksm constructed in table_load(), because
underlying devices might get resumed, and have new tables swapped in,
and might support more capabilities than before
2) a subsequent dm_swap_table() call could fail for whatever reason, and
we'll need to revert to the current ksm.
What I'm doing right now is simply freeing the ksm returned by
dm_init_inline_encryption() whenever it's called from table_load()
(and I'm trying to make that process a little nicer by wrapping it in a
function called dm_verify_inline_encryption()) - so if we're going to
have to call dm_init_inline_encryption() and then freeing the returned
ksm in table_load(), I think it might be better to continue to have
dm_verify_inline_encryption(), unless you'd prefer just open coding the
function directly.
> > +static void dm_update_keyslot_manager(struct mapped_device *md,
> > + struct blk_keyslot_manager *ksm)
> > +{
> > + bool ksm_is_empty = true;
> > + int i;
> > +
> > + /*
> > + * If the new KSM doesn't actually support any crypto modes, we may as
> > + * well set a NULL ksm.
> > + */
> > + ksm_is_empty = true;
> > + for (i = 0; i < ARRAY_SIZE(ksm->crypto_modes_supported); i++) {
> > + if (ksm->crypto_modes_supported[i]) {
> > + ksm_is_empty = false;
> > + break;
> > + }
> > + }
>
> dm_init_inline_encryption() seems like a better place for this "are no modes
> supported" logic.
>
Alright :)
> > + if (ksm_is_empty) {
> > + blk_ksm_destroy(ksm);
> > +
> > + /* At this point, md->queue->ksm must also be NULL, since we're
> > + * guaranteed that ksm is a superset of md->queue->ksm, and we
> > + * never set md->queue->ksm to a non-null empty ksm.
> > + */
> > + if (WARN_ON(md->queue->ksm))
> > + blk_ksm_register(NULL, md->queue);
> > + return;
> > + }
> > +
> > + /* Make the ksm less restrictive */
> > + if (!md->queue->ksm) {
> > + blk_ksm_register(ksm, md->queue);
> > + } else {
> > + blk_ksm_update_capabilities(md->queue->ksm, ksm);
> > + blk_ksm_destroy(ksm);
> > + }
> > +}
>
> Wouldn't it be simpler to just destroy (and free) the existing
> blk_keyslot_manager (if any), then set the new one (if it's not NULL)?
>
Yeah, I really wanted to do that too, but as I addressed above, I don't
think it's that straightforward :(
> > +static void dm_destroy_inline_encryption(struct mapped_device *md)
> > +{
> > + if (!md->queue->ksm)
> > + return;
> > + blk_ksm_destroy(md->queue->ksm);
>
> Missing kfree().
>
Thanks, will address this everywhere I call blk_ksm_destroy().
> > + blk_ksm_unregister(md->queue);
> > +}
> > +
> > +#else /* CONFIG_BLK_INLINE_ENCRYPTION */
> > +
> > +static inline struct blk_keyslot_manager *
> > +dm_init_inline_encryption(struct mapped_device *md, struct dm_table *t)
> > +{
> > + return NULL;
> > +}
>
> Seems it would be simpler for these functions to take a request_queue instead of
> a mapped_device.
>
> > /*
> > * Returns old map, which caller must destroy.
> > */
> > @@ -1959,6 +2164,7 @@ static struct dm_table *__bind(struct mapped_device *md, struct dm_table *t,
> > struct request_queue *q = md->queue;
> > bool request_based = dm_table_request_based(t);
> > sector_t size;
> > + struct blk_keyslot_manager *ksm;
> > int ret;
> >
> > lockdep_assert_held(&md->suspend_lock);
> > @@ -1994,12 +2200,21 @@ static struct dm_table *__bind(struct mapped_device *md, struct dm_table *t,
> > md->immutable_target = dm_table_get_immutable_target(t);
> > }
> >
> > + ksm = dm_init_inline_encryption(md, t);
> > + if (IS_ERR(ksm)) {
> > + old_map = ERR_PTR(PTR_ERR(ksm));
> > + goto out;
> > + }
>
> It seems too late to fail here, since the mapped_device already started being
> updated. What I suggested above would address this.
>
Alright, I'll move the call to dm_init_inline_encryption() earlier, into
dm_swap_table().
> > +#ifdef CONFIG_BLK_INLINE_ENCRYPTION
> > +
> > /**
> > * struct blk_ksm_ll_ops - functions to manage keyslots in hardware
> > * @keyslot_program: Program the specified key into the specified slot in the
> > @@ -106,6 +108,21 @@ void blk_ksm_reprogram_all_keys(struct blk_keyslot_manager *ksm);
> >
> > void blk_ksm_destroy(struct blk_keyslot_manager *ksm);
> >
> > +void blk_ksm_intersect_modes(struct blk_keyslot_manager *parent,
> > + const struct blk_keyslot_manager *child);
> > +
> > void blk_ksm_init_passthrough(struct blk_keyslot_manager *ksm);
> >
> > +bool blk_ksm_is_superset(struct blk_keyslot_manager *ksm_superset,
> > + struct blk_keyslot_manager *ksm_subset);
> > +
> > +void blk_ksm_update_capabilities(struct blk_keyslot_manager *target_ksm,
> > + struct blk_keyslot_manager *reference_ksm);
> > +
> > +#else /* CONFIG_BLK_INLINE_ENCRYPTION */
> > +
> > +static inline void blk_ksm_destroy(struct blk_keyslot_manager *ksm) { }
> > +
> > +#endif /* CONFIG_BLK_INLINE_ENCRYPTION */
>
> Is the blk_ksm_destroy() stub really needed?
>
I'm calling blk_ksm_destroy() from __bind() wihout any ifdefs, so I
think it's necessary - I'll check again just in case.
> - Eric
On Tue, Oct 27, 2020 at 11:58:47PM +0000, Satya Tangirala wrote:
> > > +/**
> > > + * blk_ksm_update_capabilities() - Update the restrictions of a KSM to those of
> > > + * another KSM
> > > + * @target_ksm: The KSM whose restrictions to update.
> > > + * @reference_ksm: The KSM to whose restrictions this function will update
> > > + * @target_ksm's restrictions to,
> > > + */
> > > +void blk_ksm_update_capabilities(struct blk_keyslot_manager *target_ksm,
> > > + struct blk_keyslot_manager *reference_ksm)
> > > +{
> > > + memcpy(target_ksm->crypto_modes_supported,
> > > + reference_ksm->crypto_modes_supported,
> > > + sizeof(target_ksm->crypto_modes_supported));
> > > +
> > > + target_ksm->max_dun_bytes_supported =
> > > + reference_ksm->max_dun_bytes_supported;
> > > +}
> > > +EXPORT_SYMBOL_GPL(blk_ksm_update_capabilities);
> >
> > Wouldn't it be easier to replace the original blk_keyslot_manager, rather than
> > modify it? Then blk_ksm_update_capabilities() wouldn't be needed.
> >
> I didn't want to replace the original blk_keyslot_manager because it's
> possible that e.g. fscrypt is checking for crypto capabilities support
> via blk_ksm_crypto_cfg_supported() when DM wants to replace the
> blk_keyslot_manager. DM would have to free the memory used by the
> blk_keyslot_manager, but blk_ksm_crypto_cfg_supported() might still
> be trying to access that memory. I did it this way to avoid having to
> add refcounts or something else to the blk_keyslot_manager...(And I
> didn't bother adding any synchronization code since the capabilities
> only ever expand, and never contract).
Are you sure that's possible? That would imply that there is no synchronization
between limits/capabilities in the request_queue being changed and the
request_queue being used. That's already buggy. Maybe it's the sort of thing
that is gotten away with in practice, in which case avoiding a free() would
indeed be a good idea, but it's worth explicitly clarifying whether all this
code is indeed racy by design...
> > > diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c
> > > index cd0478d44058..2b3efa9f9fae 100644
> > > --- a/drivers/md/dm-ioctl.c
> > > +++ b/drivers/md/dm-ioctl.c
> > > @@ -1358,6 +1358,10 @@ static int table_load(struct file *filp, struct dm_ioctl *param, size_t param_si
> > > goto err_unlock_md_type;
> > > }
> > >
> > > + r = dm_verify_inline_encryption(md, t);
> > > + if (r)
> > > + goto err_unlock_md_type;
> > > +
> > > if (dm_get_md_type(md) == DM_TYPE_NONE) {
> > > /* Initial table load: acquire type of table. */
> > > dm_set_md_type(md, dm_table_get_type(t));
> > > @@ -2114,6 +2118,10 @@ int __init dm_early_create(struct dm_ioctl *dmi,
> > > if (r)
> > > goto err_destroy_table;
> > >
> > > + r = dm_verify_inline_encryption(md, t);
> > > + if (r)
> > > + goto err_destroy_table;
> > > +
> > > md->type = dm_table_get_type(t);
> > > /* setup md->queue to reflect md's type (may block) */
> > > r = dm_setup_md_queue(md, t);
> >
> > Both table_load() and dm_early_create() call dm_setup_md_queue(). Wouldn't it
> > be simpler to handle inline encryption in dm_setup_md_queue(), instead of doing
> > it in both table_load() and dm_early_create()?
> >
> table_load() only calls dm_setup_md_queue() on initial table load (when
> the md_type is DM_TYPE_NONE), so I can't call
> dm_verify_inline_encryption() in only dm_setup_md_queue(), because
> dm_verify_inline_encryption() needs to run on every table load.
Where do all the other limitations and capabilities of the request_queue get
updated on non-initial table loads, then?
> > > +/**
> > > + * dm_verify_inline_encryption() - Verifies that the current keyslot manager of
> > > + * the mapped_device can be replaced by the
> > > + * keyslot manager of a given dm_table.
> > > + * @md: The mapped_device
> > > + * @t: The dm_table
> > > + *
> > > + * In particular, this function checks that the keyslot manager that will be
> > > + * constructed for the dm_table will support a superset of the capabilities that
> > > + * the current keyslot manager of the mapped_device supports.
> > > + *
> > > + * Return: 0 if the table's keyslot_manager can replace the current keyslot
> > > + * manager of the mapped_device. Negative value otherwise.
> > > + */
> > > +int dm_verify_inline_encryption(struct mapped_device *md, struct dm_table *t)
> > > +{
> > > + struct blk_keyslot_manager *ksm = dm_init_inline_encryption(md, t);
> > > +
> > > + if (IS_ERR(ksm))
> > > + return PTR_ERR(ksm);
> > > + blk_ksm_destroy(ksm);
> > > +
> > > + return 0;
> > > +}
> >
> > This function seems redundant with dm_init_inline_encryption(). Wouldn't it be
> > simpler to do:
> >
> > - dm_setup_md_queue() and dm_swap_table() call dm_init_inline_encryption() after
> > dm_calculate_queue_limits().
> >
> > - ksm gets passed to dm_table_set_restrictions(), which calls
> > dm_update_keyslot_manager() (maybe rename to dm_update_inline_encryption()?)
> > to actually set q->ksm.
> >
> > That way, the crypto capabilities would be handled similarly to how the
> > queue_limits are already handled.
> >
> If we call it from dm_swap_table(), we could have it pass the returned
> ksm to __bind(), either as a new argument, or by adding the ksm to the
> queue_limits (I'll have to check if that's ok/a good idea in the first
> place), and __bind() could send the argument to
> dm_table_set_restrictions()
>
> But the real issue is, I think we should check whether a new table is
> valid (from the ksm capabilities support perspective) at the time that
> table is loaded (as opposed to only checking it when DM attempts to swap
> it in, which might be a lot later, when the user resumes the device) - so
> I can't only call it from dm_setup_md_queue(), and I'd have to call it
> from table_load() anyway. And the returned ksm that table_load() obtains
> from dm_init_inline_encryption() can't really be used - because
> 1) the ksm constructed at dm_swap_table() might actually support more
> capabilities than the ksm constructed in table_load(), because
> underlying devices might get resumed, and have new tables swapped in,
> and might support more capabilities than before
> 2) a subsequent dm_swap_table() call could fail for whatever reason, and
> we'll need to revert to the current ksm.
>
> What I'm doing right now is simply freeing the ksm returned by
> dm_init_inline_encryption() whenever it's called from table_load()
> (and I'm trying to make that process a little nicer by wrapping it in a
> function called dm_verify_inline_encryption()) - so if we're going to
> have to call dm_init_inline_encryption() and then freeing the returned
> ksm in table_load(), I think it might be better to continue to have
> dm_verify_inline_encryption(), unless you'd prefer just open coding the
> function directly.
I don't understand why this needs to be so complicated. Doesn't the dm layer
have the same problem for all the other queue limits and capabilities? What
makes inline encryption different?
- Eric
On Tue, Oct 27, 2020 at 05:17:31PM -0700, Eric Biggers wrote:
> On Tue, Oct 27, 2020 at 11:58:47PM +0000, Satya Tangirala wrote:
> > > > +/**
> > > > + * blk_ksm_update_capabilities() - Update the restrictions of a KSM to those of
> > > > + * another KSM
> > > > + * @target_ksm: The KSM whose restrictions to update.
> > > > + * @reference_ksm: The KSM to whose restrictions this function will update
> > > > + * @target_ksm's restrictions to,
> > > > + */
> > > > +void blk_ksm_update_capabilities(struct blk_keyslot_manager *target_ksm,
> > > > + struct blk_keyslot_manager *reference_ksm)
> > > > +{
> > > > + memcpy(target_ksm->crypto_modes_supported,
> > > > + reference_ksm->crypto_modes_supported,
> > > > + sizeof(target_ksm->crypto_modes_supported));
> > > > +
> > > > + target_ksm->max_dun_bytes_supported =
> > > > + reference_ksm->max_dun_bytes_supported;
> > > > +}
> > > > +EXPORT_SYMBOL_GPL(blk_ksm_update_capabilities);
> > >
> > > Wouldn't it be easier to replace the original blk_keyslot_manager, rather than
> > > modify it? Then blk_ksm_update_capabilities() wouldn't be needed.
> > >
> > I didn't want to replace the original blk_keyslot_manager because it's
> > possible that e.g. fscrypt is checking for crypto capabilities support
> > via blk_ksm_crypto_cfg_supported() when DM wants to replace the
> > blk_keyslot_manager. DM would have to free the memory used by the
> > blk_keyslot_manager, but blk_ksm_crypto_cfg_supported() might still
> > be trying to access that memory. I did it this way to avoid having to
> > add refcounts or something else to the blk_keyslot_manager...(And I
> > didn't bother adding any synchronization code since the capabilities
> > only ever expand, and never contract).
>
> Are you sure that's possible? That would imply that there is no synchronization
> between limits/capabilities in the request_queue being changed and the
> request_queue being used. That's already buggy. Maybe it's the sort of thing
> that is gotten away with in practice, in which case avoiding a free() would
> indeed be a good idea, but it's worth explicitly clarifying whether all this
> code is indeed racy by design...
>
I tried checking if the two code regions are reachable at the same time
(by adding some hacky code in the middle of
blk_ksm_crypto_cfg_supported() to loop indefinitely until a certain flag
is set at the end of dm_update_keyslot_manager(), which is right after
where we'd free the old ksm when the table is swapped), and it turns out
the two regions really *can* run at the same time. Otoh, I'd imagine
dm_stop_queue() might synchronize the limits in the request_queue(), but
that's only called on request based DM devices...tl;dr I don't know if
changing limits in the request_queue is racy, but checking for crypto
capabilities is.
In case you're interested, here's the hack I used to test that
diff --git a/block/keyslot-manager.c b/block/keyslot-manager.c
index e16e4a074765..918bdd58e6b2 100644
--- a/block/keyslot-manager.c
+++ b/block/keyslot-manager.c
@@ -34,6 +34,7 @@
#include <linux/pm_runtime.h>
#include <linux/wait.h>
#include <linux/blkdev.h>
+#include <linux/delay.h>
struct blk_ksm_keyslot {
atomic_t slot_refs;
@@ -284,6 +285,7 @@ void blk_ksm_put_slot(struct blk_ksm_keyslot *slot)
}
}
+volatile int my_inline_var = 0;
/**
* blk_ksm_crypto_cfg_supported() - Find out if a crypto configuration is
* supported by a ksm.
@@ -297,8 +299,18 @@ void blk_ksm_put_slot(struct blk_ksm_keyslot *slot)
bool blk_ksm_crypto_cfg_supported(struct blk_keyslot_manager *ksm,
const struct blk_crypto_config *cfg)
{
+ int mtmp = 0;
+
if (!ksm)
return false;
+ if (my_inline_var == 0)
+ my_inline_var = 1;
+ while (my_inline_var != 3) {
+ if (mtmp % 10 == 0)
+ printk("In blk_ksm_crypto supported! %d", my_inline_var);
+ mtmp++;
+ msleep(500);
+ }
if (!(ksm->crypto_modes_supported[cfg->crypto_mode] &
cfg->data_unit_size))
return false;
diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index cb1191d6e945..c6733de1388c 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -2141,6 +2141,14 @@ static int loop_add(struct loop_device **l, int i)
if (!disk)
goto out_free_queue;
+#ifdef CONFIG_BLK_INLINE_ENCRYPTION
+ blk_ksm_init_passthrough(&lo->ksm);
+ lo->ksm.max_dun_bytes_supported = 16;
+ lo->ksm.crypto_modes_supported[BLK_ENCRYPTION_MODE_AES_256_XTS] = 0xFFFFFFFF;
+ lo->ksm.crypto_modes_supported[BLK_ENCRYPTION_MODE_ADIANTUM] = 0xFFFFFFFF;
+ blk_ksm_register(&lo->ksm, lo->lo_queue);
+#endif
+
/*
* Disable partition scanning by default. The in-kernel partition
* scanning can be requested individually per-device during its
diff --git a/drivers/block/loop.h b/drivers/block/loop.h
index af75a5ee4094..4fc9aa9cab94 100644
--- a/drivers/block/loop.h
+++ b/drivers/block/loop.h
@@ -12,6 +12,7 @@
#include <linux/bio.h>
#include <linux/blkdev.h>
#include <linux/blk-mq.h>
+#include <linux/keyslot-manager.h>
#include <linux/spinlock.h>
#include <linux/mutex.h>
#include <linux/kthread.h>
@@ -62,6 +63,9 @@ struct loop_device {
struct request_queue *lo_queue;
struct blk_mq_tag_set tag_set;
struct gendisk *lo_disk;
+#ifdef CONFIG_BLK_INLINE_ENCRYPTION
+ struct blk_keyslot_manager ksm;
+#endif
};
struct loop_cmd {
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 22bb2c90583d..165521d1ade2 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -2087,7 +2087,7 @@ int dm_verify_inline_encryption(struct mapped_device *md, struct dm_table *t)
return 0;
}
-
+extern volatile int my_inline_var;
static void dm_update_keyslot_manager(struct mapped_device *md,
struct blk_keyslot_manager *ksm)
{
@@ -2125,6 +2125,11 @@ static void dm_update_keyslot_manager(struct mapped_device *md,
blk_ksm_update_capabilities(md->queue->ksm, ksm);
blk_ksm_destroy(ksm);
}
+ printk("update KSM!");
+ if (my_inline_var == 2) {
+ printk("Update to 3 in ksm update");
+ my_inline_var = 3;
+ }
}
static void dm_destroy_inline_encryption(struct mapped_device *md)
@@ -2213,6 +2218,11 @@ static struct dm_table *__bind(struct mapped_device *md, struct dm_table *t,
goto out;
}
+ if (my_inline_var == 1) {
+ printk("Update to 2 in bind");
+ my_inline_var = 2;
+ }
+
dm_update_keyslot_manager(md, ksm);
old_map = rcu_dereference_protected(md->map, lockdep_is_held(&md->suspend_lock));
Using that patch, I
1) set up a loopback device on a file
2) set up a dm-linear device (dm-0) on that loopback device
3) suspended dm-0
4) loaded a new table to dm-0 (I just used the same table as the existing
table)
5) tried to read an encrypted file from dm-0 in the background (which
promptly started printing out "In blk_ksm_crypto supported! 1" every
5s)
6) resumed dm-0, which causes the "new" table to be swapped in, and sets
my_inline_var to 3, which eventually results in the read in step 5
to run to completion.
> > > > diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c
> > > > index cd0478d44058..2b3efa9f9fae 100644
> > > > --- a/drivers/md/dm-ioctl.c
> > > > +++ b/drivers/md/dm-ioctl.c
> > > > @@ -1358,6 +1358,10 @@ static int table_load(struct file *filp, struct dm_ioctl *param, size_t param_si
> > > > goto err_unlock_md_type;
> > > > }
> > > >
> > > > + r = dm_verify_inline_encryption(md, t);
> > > > + if (r)
> > > > + goto err_unlock_md_type;
> > > > +
> > > > if (dm_get_md_type(md) == DM_TYPE_NONE) {
> > > > /* Initial table load: acquire type of table. */
> > > > dm_set_md_type(md, dm_table_get_type(t));
> > > > @@ -2114,6 +2118,10 @@ int __init dm_early_create(struct dm_ioctl *dmi,
> > > > if (r)
> > > > goto err_destroy_table;
> > > >
> > > > + r = dm_verify_inline_encryption(md, t);
> > > > + if (r)
> > > > + goto err_destroy_table;
> > > > +
> > > > md->type = dm_table_get_type(t);
> > > > /* setup md->queue to reflect md's type (may block) */
> > > > r = dm_setup_md_queue(md, t);
> > >
> > > Both table_load() and dm_early_create() call dm_setup_md_queue(). Wouldn't it
> > > be simpler to handle inline encryption in dm_setup_md_queue(), instead of doing
> > > it in both table_load() and dm_early_create()?
> > >
> > table_load() only calls dm_setup_md_queue() on initial table load (when
> > the md_type is DM_TYPE_NONE), so I can't call
> > dm_verify_inline_encryption() in only dm_setup_md_queue(), because
> > dm_verify_inline_encryption() needs to run on every table load.
>
> Where do all the other limitations and capabilities of the request_queue get
> updated on non-initial table loads, then?
>
I don't think they get updated on non-initial table loads at all - they
only get updated on table swaps. Integrity is, however, an exception -
it gets updated on table loads, and verified on table swaps (and if
verification fails during the swap, it removes the integrity profile
entirely).
> > > > +/**
> > > > + * dm_verify_inline_encryption() - Verifies that the current keyslot manager of
> > > > + * the mapped_device can be replaced by the
> > > > + * keyslot manager of a given dm_table.
> > > > + * @md: The mapped_device
> > > > + * @t: The dm_table
> > > > + *
> > > > + * In particular, this function checks that the keyslot manager that will be
> > > > + * constructed for the dm_table will support a superset of the capabilities that
> > > > + * the current keyslot manager of the mapped_device supports.
> > > > + *
> > > > + * Return: 0 if the table's keyslot_manager can replace the current keyslot
> > > > + * manager of the mapped_device. Negative value otherwise.
> > > > + */
> > > > +int dm_verify_inline_encryption(struct mapped_device *md, struct dm_table *t)
> > > > +{
> > > > + struct blk_keyslot_manager *ksm = dm_init_inline_encryption(md, t);
> > > > +
> > > > + if (IS_ERR(ksm))
> > > > + return PTR_ERR(ksm);
> > > > + blk_ksm_destroy(ksm);
> > > > +
> > > > + return 0;
> > > > +}
> > >
> > > This function seems redundant with dm_init_inline_encryption(). Wouldn't it be
> > > simpler to do:
> > >
> > > - dm_setup_md_queue() and dm_swap_table() call dm_init_inline_encryption() after
> > > dm_calculate_queue_limits().
> > >
> > > - ksm gets passed to dm_table_set_restrictions(), which calls
> > > dm_update_keyslot_manager() (maybe rename to dm_update_inline_encryption()?)
> > > to actually set q->ksm.
> > >
> > > That way, the crypto capabilities would be handled similarly to how the
> > > queue_limits are already handled.
> > >
> > If we call it from dm_swap_table(), we could have it pass the returned
> > ksm to __bind(), either as a new argument, or by adding the ksm to the
> > queue_limits (I'll have to check if that's ok/a good idea in the first
> > place), and __bind() could send the argument to
> > dm_table_set_restrictions()
> >
> > But the real issue is, I think we should check whether a new table is
> > valid (from the ksm capabilities support perspective) at the time that
> > table is loaded (as opposed to only checking it when DM attempts to swap
> > it in, which might be a lot later, when the user resumes the device) - so
> > I can't only call it from dm_setup_md_queue(), and I'd have to call it
> > from table_load() anyway. And the returned ksm that table_load() obtains
> > from dm_init_inline_encryption() can't really be used - because
> > 1) the ksm constructed at dm_swap_table() might actually support more
> > capabilities than the ksm constructed in table_load(), because
> > underlying devices might get resumed, and have new tables swapped in,
> > and might support more capabilities than before
> > 2) a subsequent dm_swap_table() call could fail for whatever reason, and
> > we'll need to revert to the current ksm.
> >
> > What I'm doing right now is simply freeing the ksm returned by
> > dm_init_inline_encryption() whenever it's called from table_load()
> > (and I'm trying to make that process a little nicer by wrapping it in a
> > function called dm_verify_inline_encryption()) - so if we're going to
> > have to call dm_init_inline_encryption() and then freeing the returned
> > ksm in table_load(), I think it might be better to continue to have
> > dm_verify_inline_encryption(), unless you'd prefer just open coding the
> > function directly.
>
> I don't understand why this needs to be so complicated. Doesn't the dm layer
> have the same problem for all the other queue limits and capabilities? What
> makes inline encryption different?
>
It's this complicated only because I wanted to verify whether the inline
crypto capabilities of the new table are acceptable at table load time,
rather than throwing an error only at table swap time. If we decide
it's alright to throw an error only at table swap time, then
dm_verify_inline_encryption() can go away completely, and we won't need
the code in table_load() and dm_early_create() that calls that
function.
> - Eric