linux-kernel - [PATCH v3 5/6] dm: Verify inline encryption capabilities of new table when it is loaded

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Message-Id: <20201229085524.2795331-6-satyat@google.com>
Date:   Tue, 29 Dec 2020 08:55:23 +0000
From:   Satya Tangirala <satyat@...gle.com>
To:     linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        dm-devel@...hat.com
Cc:     Jens Axboe <axboe@...nel.dk>, Alasdair Kergon <agk@...hat.com>,
        Mike Snitzer <snitzer@...hat.com>,
        Eric Biggers <ebiggers@...gle.com>,
        Satya Tangirala <satyat@...gle.com>
Subject: [PATCH v3 5/6] dm: Verify inline encryption capabilities of new table
 when it is loaded

DM only allows the table to be swapped if the new table's inline encryption
capabilities are a superset of the old table's. We only check that this
constraint is true when the table is actually swapped in (in
dm_swap_table()). But this allows a user to load an unacceptable table
without any complaint from DM, only for DM to throw an error when the
device is resumed, and the table is swapped in.

This patch makes DM verify the inline encryption capabilities of the new
table when the table is loaded. DM continues to verify and use the
capabilities at the time of table swap, since the capabilities of
underlying child devices can expand during the time between the table load
and table swap (which in turn can cause the capabilities of this parent
device to expand as well).

Signed-off-by: Satya Tangirala <satyat@...gle.com>
---
 drivers/md/dm-ioctl.c |  8 ++++++++
 drivers/md/dm.c       | 25 +++++++++++++++++++++++++
 drivers/md/dm.h       | 19 +++++++++++++++++++
 3 files changed, 52 insertions(+)

diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c
index 5e306bba4375..055a3c745243 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));
@@ -2115,6 +2119,10 @@ 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 b8844171d8e4..04322de34d29 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -2094,6 +2094,31 @@ dm_construct_keyslot_manager(struct mapped_device *md, struct dm_table *t)
 	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_construct_keyslot_manager(md, t);
+
+	if (IS_ERR(ksm))
+		return PTR_ERR(ksm);
+	dm_destroy_keyslot_manager(ksm);
+
+	return 0;
+}
+
 static void dm_update_keyslot_manager(struct request_queue *q,
 				      struct blk_keyslot_manager *ksm)
 {
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
-- 
2.29.2.729.g45daf8777d-goog