[PATCH 5.10 0/3] blk-crypto fixes for 5.10

[PATCH 5.10 0/3] blk-crypto fixes for 5.10

[Eric Biggers]

This series backports some blk-crypto fixes to 5.10.

Eric Biggers (3):
  blk-mq: release crypto keyslot before reporting I/O complete
  blk-crypto: make blk_crypto_evict_key() return void
  blk-crypto: make blk_crypto_evict_key() more robust

 block/blk-core.c            |  7 ++++
 block/blk-crypto-internal.h | 25 +++++++++++---
 block/blk-crypto.c          | 69 +++++++++++++++++++++----------------
 block/blk-merge.c           |  2 ++
 block/blk-mq.c              |  2 +-
 block/keyslot-manager.c     | 43 +++++++++++------------
 include/linux/blk-crypto.h  |  4 +--
 7 files changed, 94 insertions(+), 58 deletions(-)


base-commit: f1b32fda06d2cfb8eea9680b0ba7a8b0d5b81eeb
-- 
2.40.1

[PATCH 5.10 1/3] blk-mq: release crypto keyslot before reporting I/O complete

[Eric Biggers]

From: Eric Biggers <ebiggers@google.com>

commit 9cd1e566676bbcb8a126acd921e4e194e6339603 upstream.

Once all I/O using a blk_crypto_key has completed, filesystems can call
blk_crypto_evict_key().  However, the block layer currently doesn't call
blk_crypto_put_keyslot() until the request is being freed, which happens
after upper layers have been told (via bio_endio()) the I/O has
completed.  This causes a race condition where blk_crypto_evict_key()
can see 'slot_refs != 0' without there being an actual bug.

This makes __blk_crypto_evict_key() hit the
'WARN_ON_ONCE(atomic_read(&slot->slot_refs) != 0)' and return without
doing anything, eventually causing a use-after-free in
blk_crypto_reprogram_all_keys().  (This is a very rare bug and has only
been seen when per-file keys are being used with fscrypt.)

There are two options to fix this: either release the keyslot before
bio_endio() is called on the request's last bio, or make
__blk_crypto_evict_key() ignore slot_refs.  Let's go with the first
solution, since it preserves the ability to report bugs (via
WARN_ON_ONCE) where a key is evicted while still in-use.

Fixes: a892c8d52c02 ("block: Inline encryption support for blk-mq")
Cc: stable@vger.kernel.org
Reviewed-by: Nathan Huckleberry <nhuck@google.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Link: https://lore.kernel.org/r/20230315183907.53675-2-ebiggers@kernel.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
 block/blk-core.c            |  7 +++++++
 block/blk-crypto-internal.h | 25 +++++++++++++++++++++----
 block/blk-crypto.c          | 24 ++++++++++++------------
 block/blk-merge.c           |  2 ++
 block/blk-mq.c              |  2 +-
 5 files changed, 43 insertions(+), 17 deletions(-)

diff --git a/block/blk-core.c b/block/blk-core.c
index 9afb79b322fb0..d0d0dd8151f75 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -1444,6 +1444,13 @@ bool blk_update_request(struct request *req, blk_status_t error,
 		req->q->integrity.profile->complete_fn(req, nr_bytes);
 #endif
 
+	/*
+	 * Upper layers may call blk_crypto_evict_key() anytime after the last
+	 * bio_endio().  Therefore, the keyslot must be released before that.
+	 */
+	if (blk_crypto_rq_has_keyslot(req) && nr_bytes >= blk_rq_bytes(req))
+		__blk_crypto_rq_put_keyslot(req);
+
 	if (unlikely(error && !blk_rq_is_passthrough(req) &&
 		     !(req->rq_flags & RQF_QUIET)))
 		print_req_error(req, error, __func__);
diff --git a/block/blk-crypto-internal.h b/block/blk-crypto-internal.h
index 0d36aae538d7b..8e08345576203 100644
--- a/block/blk-crypto-internal.h
+++ b/block/blk-crypto-internal.h
@@ -60,6 +60,11 @@ static inline bool blk_crypto_rq_is_encrypted(struct request *rq)
 	return rq->crypt_ctx;
 }
 
+static inline bool blk_crypto_rq_has_keyslot(struct request *rq)
+{
+	return rq->crypt_keyslot;
+}
+
 #else /* CONFIG_BLK_INLINE_ENCRYPTION */
 
 static inline bool bio_crypt_rq_ctx_compatible(struct request *rq,
@@ -93,6 +98,11 @@ static inline bool blk_crypto_rq_is_encrypted(struct request *rq)
 	return false;
 }
 
+static inline bool blk_crypto_rq_has_keyslot(struct request *rq)
+{
+	return false;
+}
+
 #endif /* CONFIG_BLK_INLINE_ENCRYPTION */
 
 void __bio_crypt_advance(struct bio *bio, unsigned int bytes);
@@ -127,14 +137,21 @@ static inline bool blk_crypto_bio_prep(struct bio **bio_ptr)
 	return true;
 }
 
-blk_status_t __blk_crypto_init_request(struct request *rq);
-static inline blk_status_t blk_crypto_init_request(struct request *rq)
+blk_status_t __blk_crypto_rq_get_keyslot(struct request *rq);
+static inline blk_status_t blk_crypto_rq_get_keyslot(struct request *rq)
 {
 	if (blk_crypto_rq_is_encrypted(rq))
-		return __blk_crypto_init_request(rq);
+		return __blk_crypto_rq_get_keyslot(rq);
 	return BLK_STS_OK;
 }
 
+void __blk_crypto_rq_put_keyslot(struct request *rq);
+static inline void blk_crypto_rq_put_keyslot(struct request *rq)
+{
+	if (blk_crypto_rq_has_keyslot(rq))
+		__blk_crypto_rq_put_keyslot(rq);
+}
+
 void __blk_crypto_free_request(struct request *rq);
 static inline void blk_crypto_free_request(struct request *rq)
 {
@@ -173,7 +190,7 @@ static inline blk_status_t blk_crypto_insert_cloned_request(struct request *rq)
 {
 
 	if (blk_crypto_rq_is_encrypted(rq))
-		return blk_crypto_init_request(rq);
+		return blk_crypto_rq_get_keyslot(rq);
 	return BLK_STS_OK;
 }
 
diff --git a/block/blk-crypto.c b/block/blk-crypto.c
index 5ffa9aab49de0..0506adfd9ca6b 100644
--- a/block/blk-crypto.c
+++ b/block/blk-crypto.c
@@ -216,26 +216,26 @@ static bool bio_crypt_check_alignment(struct bio *bio)
 	return true;
 }
 
-blk_status_t __blk_crypto_init_request(struct request *rq)
+blk_status_t __blk_crypto_rq_get_keyslot(struct request *rq)
 {
 	return blk_ksm_get_slot_for_key(rq->q->ksm, rq->crypt_ctx->bc_key,
 					&rq->crypt_keyslot);
 }
 
-/**
- * __blk_crypto_free_request - Uninitialize the crypto fields of a request.
- *
- * @rq: The request whose crypto fields to uninitialize.
- *
- * Completely uninitializes the crypto fields of a request. If a keyslot has
- * been programmed into some inline encryption hardware, that keyslot is
- * released. The rq->crypt_ctx is also freed.
- */
-void __blk_crypto_free_request(struct request *rq)
+void __blk_crypto_rq_put_keyslot(struct request *rq)
 {
 	blk_ksm_put_slot(rq->crypt_keyslot);
+	rq->crypt_keyslot = NULL;
+}
+
+void __blk_crypto_free_request(struct request *rq)
+{
+	/* The keyslot, if one was needed, should have been released earlier. */
+	if (WARN_ON_ONCE(rq->crypt_keyslot))
+		__blk_crypto_rq_put_keyslot(rq);
+
 	mempool_free(rq->crypt_ctx, bio_crypt_ctx_pool);
-	blk_crypto_rq_set_defaults(rq);
+	rq->crypt_ctx = NULL;
 }
 
 /**
diff --git a/block/blk-merge.c b/block/blk-merge.c
index fbba277364f01..f3b016b31af86 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -801,6 +801,8 @@ static struct request *attempt_merge(struct request_queue *q,
 	if (!blk_discard_mergable(req))
 		elv_merge_requests(q, req, next);
 
+	blk_crypto_rq_put_keyslot(next);
+
 	/*
 	 * 'next' is going away, so update stats accordingly
 	 */
diff --git a/block/blk-mq.c b/block/blk-mq.c
index cf66de0f00fd3..e153a36c9ba3a 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2193,7 +2193,7 @@ blk_qc_t blk_mq_submit_bio(struct bio *bio)
 
 	blk_mq_bio_to_request(rq, bio, nr_segs);
 
-	ret = blk_crypto_init_request(rq);
+	ret = blk_crypto_rq_get_keyslot(rq);
 	if (ret != BLK_STS_OK) {
 		bio->bi_status = ret;
 		bio_endio(bio);
-- 
2.40.1

[PATCH 5.10 2/3] blk-crypto: make blk_crypto_evict_key() return void

[Eric Biggers]

From: Eric Biggers <ebiggers@google.com>

commit 70493a63ba04f754f7a7dd53a4fcc82700181490 upstream.

blk_crypto_evict_key() is only called in contexts such as inode eviction
where failure is not an option.  So there is nothing the caller can do
with errors except log them.  (dm-table.c does "use" the error code, but
only to pass on to upper layers, so it doesn't really count.)

Just make blk_crypto_evict_key() return void and log errors itself.

Cc: stable@vger.kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20230315183907.53675-2-ebiggers@kernel.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
 block/blk-crypto.c         | 22 ++++++++++------------
 include/linux/blk-crypto.h |  4 ++--
 2 files changed, 12 insertions(+), 14 deletions(-)

diff --git a/block/blk-crypto.c b/block/blk-crypto.c
index 0506adfd9ca6b..d8c48ee44ba69 100644
--- a/block/blk-crypto.c
+++ b/block/blk-crypto.c
@@ -13,6 +13,7 @@
 #include <linux/blkdev.h>
 #include <linux/keyslot-manager.h>
 #include <linux/module.h>
+#include <linux/ratelimit.h>
 #include <linux/slab.h>
 
 #include "blk-crypto-internal.h"
@@ -393,19 +394,16 @@ int blk_crypto_start_using_key(const struct blk_crypto_key *key,
  * Upper layers (filesystems) must call this function to ensure that a key is
  * evicted from any hardware that it might have been programmed into.  The key
  * must not be in use by any in-flight IO when this function is called.
- *
- * Return: 0 on success or if key is not present in the q's ksm, -err on error.
  */
-int blk_crypto_evict_key(struct request_queue *q,
-			 const struct blk_crypto_key *key)
+void blk_crypto_evict_key(struct request_queue *q,
+			  const struct blk_crypto_key *key)
 {
-	if (blk_ksm_crypto_cfg_supported(q->ksm, &key->crypto_cfg))
-		return blk_ksm_evict_key(q->ksm, key);
+	int err;
 
-	/*
-	 * If the request queue's associated inline encryption hardware didn't
-	 * have support for the key, then the key might have been programmed
-	 * into the fallback keyslot manager, so try to evict from there.
-	 */
-	return blk_crypto_fallback_evict_key(key);
+	if (blk_ksm_crypto_cfg_supported(q->ksm, &key->crypto_cfg))
+		err = blk_ksm_evict_key(q->ksm, key);
+	else
+		err = blk_crypto_fallback_evict_key(key);
+	if (err)
+		pr_warn_ratelimited("error %d evicting key\n", err);
 }
diff --git a/include/linux/blk-crypto.h b/include/linux/blk-crypto.h
index 69b24fe92cbf1..5e96bad548047 100644
--- a/include/linux/blk-crypto.h
+++ b/include/linux/blk-crypto.h
@@ -97,8 +97,8 @@ int blk_crypto_init_key(struct blk_crypto_key *blk_key, const u8 *raw_key,
 int blk_crypto_start_using_key(const struct blk_crypto_key *key,
 			       struct request_queue *q);
 
-int blk_crypto_evict_key(struct request_queue *q,
-			 const struct blk_crypto_key *key);
+void blk_crypto_evict_key(struct request_queue *q,
+			  const struct blk_crypto_key *key);
 
 bool blk_crypto_config_supported(struct request_queue *q,
 				 const struct blk_crypto_config *cfg);
-- 
2.40.1

[PATCH 5.10 3/3] blk-crypto: make blk_crypto_evict_key() more robust

[Eric Biggers]

From: Eric Biggers <ebiggers@google.com>

commit 5c7cb94452901a93e90c2230632e2c12a681bc92 upstream.

If blk_crypto_evict_key() sees that the key is still in-use (due to a
bug) or that ->keyslot_evict failed, it currently just returns while
leaving the key linked into the keyslot management structures.

However, blk_crypto_evict_key() is only called in contexts such as inode
eviction where failure is not an option.  So actually the caller
proceeds with freeing the blk_crypto_key regardless of the return value
of blk_crypto_evict_key().

These two assumptions don't match, and the result is that there can be a
use-after-free in blk_crypto_reprogram_all_keys() after one of these
errors occurs.  (Note, these errors *shouldn't* happen; we're just
talking about what happens if they do anyway.)

Fix this by making blk_crypto_evict_key() unlink the key from the
keyslot management structures even on failure.

Also improve some comments.

Fixes: 1b2628397058 ("block: Keyslot Manager for Inline Encryption")
Cc: stable@vger.kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20230315183907.53675-2-ebiggers@kernel.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
 block/blk-crypto.c      | 29 +++++++++++++++++++--------
 block/keyslot-manager.c | 43 ++++++++++++++++++++---------------------
 2 files changed, 42 insertions(+), 30 deletions(-)

diff --git a/block/blk-crypto.c b/block/blk-crypto.c
index d8c48ee44ba69..87ec55d4354f5 100644
--- a/block/blk-crypto.c
+++ b/block/blk-crypto.c
@@ -385,15 +385,20 @@ int blk_crypto_start_using_key(const struct blk_crypto_key *key,
 }
 
 /**
- * blk_crypto_evict_key() - Evict a key from any inline encryption hardware
- *			    it may have been programmed into
- * @q: The request queue who's associated inline encryption hardware this key
- *     might have been programmed into
- * @key: The key to evict
+ * blk_crypto_evict_key() - Evict a blk_crypto_key from a request_queue
+ * @q: a request_queue on which I/O using the key may have been done
+ * @key: the key to evict
  *
- * Upper layers (filesystems) must call this function to ensure that a key is
- * evicted from any hardware that it might have been programmed into.  The key
- * must not be in use by any in-flight IO when this function is called.
+ * For a given request_queue, this function removes the given blk_crypto_key
+ * from the keyslot management structures and evicts it from any underlying
+ * hardware keyslot(s) or blk-crypto-fallback keyslot it may have been
+ * programmed into.
+ *
+ * Upper layers must call this before freeing the blk_crypto_key.  It must be
+ * called for every request_queue the key may have been used on.  The key must
+ * no longer be in use by any I/O when this function is called.
+ *
+ * Context: May sleep.
  */
 void blk_crypto_evict_key(struct request_queue *q,
 			  const struct blk_crypto_key *key)
@@ -404,6 +409,14 @@ void blk_crypto_evict_key(struct request_queue *q,
 		err = blk_ksm_evict_key(q->ksm, key);
 	else
 		err = blk_crypto_fallback_evict_key(key);
+	/*
+	 * An error can only occur here if the key failed to be evicted from a
+	 * keyslot (due to a hardware or driver issue) or is allegedly still in
+	 * use by I/O (due to a kernel bug).  Even in these cases, the key is
+	 * still unlinked from the keyslot management structures, and the caller
+	 * is allowed and expected to free it right away.  There's nothing
+	 * callers can do to handle errors, so just log them and return void.
+	 */
 	if (err)
 		pr_warn_ratelimited("error %d evicting key\n", err);
 }
diff --git a/block/keyslot-manager.c b/block/keyslot-manager.c
index 86f8195d8039e..17a1f1ba44efc 100644
--- a/block/keyslot-manager.c
+++ b/block/keyslot-manager.c
@@ -305,44 +305,43 @@ bool blk_ksm_crypto_cfg_supported(struct blk_keyslot_manager *ksm,
 	return true;
 }
 
-/**
- * blk_ksm_evict_key() - Evict a key from the lower layer device.
- * @ksm: The keyslot manager to evict from
- * @key: The key to evict
- *
- * Find the keyslot that the specified key was programmed into, and evict that
- * slot from the lower layer device. The slot must not be in use by any
- * in-flight IO when this function is called.
- *
- * Context: Process context. Takes and releases ksm->lock.
- * Return: 0 on success or if there's no keyslot with the specified key, -EBUSY
- *	   if the keyslot is still in use, or another -errno value on other
- *	   error.
+/*
+ * This is an internal function that evicts a key from an inline encryption
+ * device that can be either a real device or the blk-crypto-fallback "device".
+ * It is used only by blk_crypto_evict_key(); see that function for details.
  */
 int blk_ksm_evict_key(struct blk_keyslot_manager *ksm,
 		      const struct blk_crypto_key *key)
 {
 	struct blk_ksm_keyslot *slot;
-	int err = 0;
+	int err;
 
 	blk_ksm_hw_enter(ksm);
 	slot = blk_ksm_find_keyslot(ksm, key);
-	if (!slot)
-		goto out_unlock;
+	if (!slot) {
+		/*
+		 * Not an error, since a key not in use by I/O is not guaranteed
+		 * to be in a keyslot.  There can be more keys than keyslots.
+		 */
+		err = 0;
+		goto out;
+	}
 
 	if (WARN_ON_ONCE(atomic_read(&slot->slot_refs) != 0)) {
+		/* BUG: key is still in use by I/O */
 		err = -EBUSY;
-		goto out_unlock;
+		goto out_remove;
 	}
 	err = ksm->ksm_ll_ops.keyslot_evict(ksm, key,
 					    blk_ksm_get_slot_idx(slot));
-	if (err)
-		goto out_unlock;
-
+out_remove:
+	/*
+	 * Callers free the key even on error, so unlink the key from the hash
+	 * table and clear slot->key even on error.
+	 */
 	hlist_del(&slot->hash_node);
 	slot->key = NULL;
-	err = 0;
-out_unlock:
+out:
 	blk_ksm_hw_exit(ksm);
 	return err;
 }
-- 
2.40.1