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

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

[Eric Biggers]

From: Eric Biggers <ebiggers@google.com>

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
Signed-off-by: Eric Biggers <ebiggers@google.com>
---
 block/blk-crypto-internal.h | 15 +++++++++++----
 block/blk-crypto.c          | 24 ++++++++++++------------
 block/blk-mq.c              | 15 ++++++++++++++-
 3 files changed, 37 insertions(+), 17 deletions(-)

diff --git a/block/blk-crypto-internal.h b/block/blk-crypto-internal.h
index a8cdaf26851e1..73609902349b6 100644
--- a/block/blk-crypto-internal.h
+++ b/block/blk-crypto-internal.h
@@ -153,14 +153,21 @@ 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_is_encrypted(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)
 {
@@ -199,7 +206,7 @@ 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 45378586151f7..8e5612364c48c 100644
--- a/block/blk-crypto.c
+++ b/block/blk-crypto.c
@@ -224,27 +224,27 @@ 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_crypto_get_keyslot(rq->q->crypto_profile,
 				      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_crypto_put_keyslot(rq->crypt_keyslot);
+	rq->crypt_keyslot = NULL;
+}
+
+void __blk_crypto_free_request(struct request *rq)
+{
 	mempool_free(rq->crypt_ctx, bio_crypt_ctx_pool);
-	blk_crypto_rq_set_defaults(rq);
+	rq->crypt_ctx = NULL;
+
+	/* The keyslot, if one was needed, should have been released earlier. */
+	if (WARN_ON_ONCE(rq->crypt_keyslot))
+		__blk_crypto_rq_put_keyslot(rq);
 }
 
 /**
diff --git a/block/blk-mq.c b/block/blk-mq.c
index d3494a796ba80..738e81f518227 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -840,6 +840,12 @@ static void blk_complete_request(struct request *req)
 		req->q->integrity.profile->complete_fn(req, total_bytes);
 #endif
 
+	/*
+	 * Upper layers may call blk_crypto_evict_key() anytime after the last
+	 * bio_endio().  Therefore, the keyslot must be released before that.
+	 */
+	blk_crypto_rq_put_keyslot(req);
+
 	blk_account_io_completion(req, total_bytes);
 
 	do {
@@ -905,6 +911,13 @@ 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_is_encrypted(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)) &&
 		     !test_bit(GD_DEAD, &req->q->disk->state)) {
@@ -2967,7 +2980,7 @@ void 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);
-- 
2.39.2

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

[Nathan Huckleberry]

Hi Eric,

On Thu, Mar 2, 2023 at 11:23 PM Eric Biggers <ebiggers@kernel.org> wrote:
>
> From: Eric Biggers <ebiggers@google.com>
>
> 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
> Signed-off-by: Eric Biggers <ebiggers@google.com>
> ---
>  block/blk-crypto-internal.h | 15 +++++++++++----
>  block/blk-crypto.c          | 24 ++++++++++++------------
>  block/blk-mq.c              | 15 ++++++++++++++-
>  3 files changed, 37 insertions(+), 17 deletions(-)
>
> diff --git a/block/blk-crypto-internal.h b/block/blk-crypto-internal.h
> index a8cdaf26851e1..73609902349b6 100644
> --- a/block/blk-crypto-internal.h
> +++ b/block/blk-crypto-internal.h
> @@ -153,14 +153,21 @@ 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_is_encrypted(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)
>  {
> @@ -199,7 +206,7 @@ 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 45378586151f7..8e5612364c48c 100644
> --- a/block/blk-crypto.c
> +++ b/block/blk-crypto.c
> @@ -224,27 +224,27 @@ 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_crypto_get_keyslot(rq->q->crypto_profile,
>                                       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_crypto_put_keyslot(rq->crypt_keyslot);
> +       rq->crypt_keyslot = NULL;
> +}
> +
> +void __blk_crypto_free_request(struct request *rq)
> +{
>         mempool_free(rq->crypt_ctx, bio_crypt_ctx_pool);
> -       blk_crypto_rq_set_defaults(rq);
> +       rq->crypt_ctx = NULL;
> +
> +       /* The keyslot, if one was needed, should have been released earlier. */
> +       if (WARN_ON_ONCE(rq->crypt_keyslot))
> +               __blk_crypto_rq_put_keyslot(rq);
>  }
>
>  /**
> diff --git a/block/blk-mq.c b/block/blk-mq.c
> index d3494a796ba80..738e81f518227 100644
> --- a/block/blk-mq.c
> +++ b/block/blk-mq.c
> @@ -840,6 +840,12 @@ static void blk_complete_request(struct request *req)
>                 req->q->integrity.profile->complete_fn(req, total_bytes);
>  #endif
>
> +       /*
> +        * Upper layers may call blk_crypto_evict_key() anytime after the last
> +        * bio_endio().  Therefore, the keyslot must be released before that.
> +        */
> +       blk_crypto_rq_put_keyslot(req);
> +
>         blk_account_io_completion(req, total_bytes);
>
>         do {
> @@ -905,6 +911,13 @@ 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_is_encrypted(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)) &&
>                      !test_bit(GD_DEAD, &req->q->disk->state)) {
> @@ -2967,7 +2980,7 @@ void 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);
> --
> 2.39.2
>

Thanks for the updated patchset. This patch looks good to me.

Reviewed-by: Nathan Huckleberry <nhuck@google.com>

Thanks,
Huck

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

[Eric Biggers]

On Thu, Mar 02, 2023 at 11:19:57PM -0800, Eric Biggers wrote:
> +void __blk_crypto_free_request(struct request *rq)
> +{
>  	mempool_free(rq->crypt_ctx, bio_crypt_ctx_pool);
> -	blk_crypto_rq_set_defaults(rq);
> +	rq->crypt_ctx = NULL;
> +
> +	/* The keyslot, if one was needed, should have been released earlier. */
> +	if (WARN_ON_ONCE(rq->crypt_keyslot))
> +		__blk_crypto_rq_put_keyslot(rq);
>  }

I received a report that this WARN_ON_ONCE can be hit.

To fix this, attempt_merge() will need to release the keyslot too.

- Eric

[PATCH 2/3] blk-crypto: make blk_crypto_evict_key() more robust

[Eric Biggers]

From: Eric Biggers <ebiggers@google.com>

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 an error
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.

Fixes: 1b2628397058 ("block: Keyslot Manager for Inline Encryption")
Cc: stable@vger.kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
---
 block/blk-crypto-profile.c | 50 +++++++++++++++-----------------------
 block/blk-crypto.c         | 23 +++++++++++-------
 2 files changed, 33 insertions(+), 40 deletions(-)

diff --git a/block/blk-crypto-profile.c b/block/blk-crypto-profile.c
index 0307fb0d95d34..1b20ead59f39b 100644
--- a/block/blk-crypto-profile.c
+++ b/block/blk-crypto-profile.c
@@ -354,22 +354,10 @@ bool __blk_crypto_cfg_supported(struct blk_crypto_profile *profile,
 	return true;
 }
 
-/**
- * __blk_crypto_evict_key() - Evict a key from a device.
- * @profile: the crypto profile of the device
- * @key: the key to evict.  It must not still be used in any I/O.
- *
- * If the device has keyslots, this finds the keyslot (if any) that contains the
- * specified key and calls the driver's keyslot_evict function to evict it.
- *
- * Otherwise, this just calls the driver's keyslot_evict function if it is
- * implemented, passing just the key (without any particular keyslot).  This
- * allows layered devices to evict the key from their underlying devices.
- *
- * Context: Process context. Takes and releases profile->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_crypto_evict_key(struct blk_crypto_profile *profile,
 			   const struct blk_crypto_key *key)
@@ -389,22 +377,22 @@ int __blk_crypto_evict_key(struct blk_crypto_profile *profile,
 
 	blk_crypto_hw_enter(profile);
 	slot = blk_crypto_find_keyslot(profile, key);
-	if (!slot)
-		goto out_unlock;
-
-	if (WARN_ON_ONCE(atomic_read(&slot->slot_refs) != 0)) {
-		err = -EBUSY;
-		goto out_unlock;
+	if (slot) {
+		if (WARN_ON_ONCE(atomic_read(&slot->slot_refs) != 0)) {
+			/* BUG: key is still in use by I/O */
+			err = -EBUSY;
+		} else {
+			err = profile->ll_ops.keyslot_evict(
+					profile, key,
+					blk_crypto_keyslot_index(slot));
+		}
+		/*
+		 * Callers may 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 = profile->ll_ops.keyslot_evict(profile, key,
-					    blk_crypto_keyslot_index(slot));
-	if (err)
-		goto out_unlock;
-
-	hlist_del(&slot->hash_node);
-	slot->key = NULL;
-	err = 0;
-out_unlock:
 	blk_crypto_hw_exit(profile);
 	return err;
 }
diff --git a/block/blk-crypto.c b/block/blk-crypto.c
index 8e5612364c48c..caa86a210cb6c 100644
--- a/block/blk-crypto.c
+++ b/block/blk-crypto.c
@@ -399,17 +399,22 @@ int blk_crypto_start_using_key(struct block_device *bdev,
 }
 
 /**
- * blk_crypto_evict_key() - Evict a key from any inline encryption hardware
- *			    it may have been programmed into
- * @bdev: The block_device 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 block_device
+ * @bdev: a block_device 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 block_device, 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.
  *
- * Return: 0 on success or if the key wasn't in any keyslot; -errno on error.
+ * Upper layers must call this before freeing the blk_crypto_key.  It must be
+ * called for every block_device 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.
+ * Return: 0 on success or if the key wasn't in any keyslot; -errno if the key
+ *	   failed to be evicted from a keyslot or is still in-use.  Even on
+ *	   "failure", the key is removed from the keyslot management structures.
  */
 int blk_crypto_evict_key(struct block_device *bdev,
 			 const struct blk_crypto_key *key)
-- 
2.39.2

Re: [PATCH 2/3] blk-crypto: make blk_crypto_evict_key() more robust

[Nathan Huckleberry]

Hi Eric,

On Thu, Mar 2, 2023 at 11:23 PM Eric Biggers <ebiggers@kernel.org> wrote:
>
> From: Eric Biggers <ebiggers@google.com>
>
> 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 an error
> 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.
>
> Fixes: 1b2628397058 ("block: Keyslot Manager for Inline Encryption")
> Cc: stable@vger.kernel.org
> Signed-off-by: Eric Biggers <ebiggers@google.com>
> ---
>  block/blk-crypto-profile.c | 50 +++++++++++++++-----------------------
>  block/blk-crypto.c         | 23 +++++++++++-------
>  2 files changed, 33 insertions(+), 40 deletions(-)
>
> diff --git a/block/blk-crypto-profile.c b/block/blk-crypto-profile.c
> index 0307fb0d95d34..1b20ead59f39b 100644
> --- a/block/blk-crypto-profile.c
> +++ b/block/blk-crypto-profile.c
> @@ -354,22 +354,10 @@ bool __blk_crypto_cfg_supported(struct blk_crypto_profile *profile,
>         return true;
>  }
>
> -/**
> - * __blk_crypto_evict_key() - Evict a key from a device.
> - * @profile: the crypto profile of the device
> - * @key: the key to evict.  It must not still be used in any I/O.
> - *
> - * If the device has keyslots, this finds the keyslot (if any) that contains the
> - * specified key and calls the driver's keyslot_evict function to evict it.
> - *
> - * Otherwise, this just calls the driver's keyslot_evict function if it is
> - * implemented, passing just the key (without any particular keyslot).  This
> - * allows layered devices to evict the key from their underlying devices.
> - *
> - * Context: Process context. Takes and releases profile->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_crypto_evict_key(struct blk_crypto_profile *profile,
>                            const struct blk_crypto_key *key)
> @@ -389,22 +377,22 @@ int __blk_crypto_evict_key(struct blk_crypto_profile *profile,
>
>         blk_crypto_hw_enter(profile);
>         slot = blk_crypto_find_keyslot(profile, key);
> -       if (!slot)
> -               goto out_unlock;
> -
> -       if (WARN_ON_ONCE(atomic_read(&slot->slot_refs) != 0)) {
> -               err = -EBUSY;
> -               goto out_unlock;
> +       if (slot) {
> +               if (WARN_ON_ONCE(atomic_read(&slot->slot_refs) != 0)) {
> +                       /* BUG: key is still in use by I/O */
> +                       err = -EBUSY;
> +               } else {
> +                       err = profile->ll_ops.keyslot_evict(
> +                                       profile, key,
> +                                       blk_crypto_keyslot_index(slot));
> +               }
> +               /*
> +                * Callers may 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;
>         }

The !slot case still needs to be handled. If profile->num_slots != 0
and !slot, we'll get an invalid index from blk_crypto_keyslot_index.

With that change,
Reviewed-by: Nathan Huckleberry <nhuck@google.com>

Thanks,
Huck

> -       err = profile->ll_ops.keyslot_evict(profile, key,
> -                                           blk_crypto_keyslot_index(slot));
> -       if (err)
> -               goto out_unlock;
> -
> -       hlist_del(&slot->hash_node);
> -       slot->key = NULL;
> -       err = 0;
> -out_unlock:
>         blk_crypto_hw_exit(profile);
>         return err;
>  }
> diff --git a/block/blk-crypto.c b/block/blk-crypto.c
> index 8e5612364c48c..caa86a210cb6c 100644
> --- a/block/blk-crypto.c
> +++ b/block/blk-crypto.c
> @@ -399,17 +399,22 @@ int blk_crypto_start_using_key(struct block_device *bdev,
>  }
>
>  /**
> - * blk_crypto_evict_key() - Evict a key from any inline encryption hardware
> - *                         it may have been programmed into
> - * @bdev: The block_device 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 block_device
> + * @bdev: a block_device 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 block_device, 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.
>   *
> - * Return: 0 on success or if the key wasn't in any keyslot; -errno on error.
> + * Upper layers must call this before freeing the blk_crypto_key.  It must be
> + * called for every block_device 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.
> + * Return: 0 on success or if the key wasn't in any keyslot; -errno if the key
> + *        failed to be evicted from a keyslot or is still in-use.  Even on
> + *        "failure", the key is removed from the keyslot management structures.
>   */
>  int blk_crypto_evict_key(struct block_device *bdev,
>                          const struct blk_crypto_key *key)
> --
> 2.39.2
>

Re: [PATCH 2/3] blk-crypto: make blk_crypto_evict_key() more robust

[Eric Biggers]

On Fri, Mar 03, 2023 at 11:45:00AM -0800, Nathan Huckleberry wrote:
> >  int __blk_crypto_evict_key(struct blk_crypto_profile *profile,
> >                            const struct blk_crypto_key *key)
> > @@ -389,22 +377,22 @@ int __blk_crypto_evict_key(struct blk_crypto_profile *profile,
> >
> >         blk_crypto_hw_enter(profile);
> >         slot = blk_crypto_find_keyslot(profile, key);
> > -       if (!slot)
> > -               goto out_unlock;
> > -
> > -       if (WARN_ON_ONCE(atomic_read(&slot->slot_refs) != 0)) {
> > -               err = -EBUSY;
> > -               goto out_unlock;
> > +       if (slot) {
> > +               if (WARN_ON_ONCE(atomic_read(&slot->slot_refs) != 0)) {
> > +                       /* BUG: key is still in use by I/O */
> > +                       err = -EBUSY;
> > +               } else {
> > +                       err = profile->ll_ops.keyslot_evict(
> > +                                       profile, key,
> > +                                       blk_crypto_keyslot_index(slot));
> > +               }
> > +               /*
> > +                * Callers may 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;
> >         }
> 
> The !slot case still needs to be handled. If profile->num_slots != 0
> and !slot, we'll get an invalid index from blk_crypto_keyslot_index.
> 
> With that change,
> Reviewed-by: Nathan Huckleberry <nhuck@google.com>
> 
> Thanks,
> Huck
> 
> > -       err = profile->ll_ops.keyslot_evict(profile, key,
> > -                                           blk_crypto_keyslot_index(slot));
> > -       if (err)
> > -               goto out_unlock;
> > -
> > -       hlist_del(&slot->hash_node);
> > -       slot->key = NULL;
> > -       err = 0;
> > -out_unlock:
> >         blk_crypto_hw_exit(profile);
> >         return err;
> >  }

I'm not sure what you're referring to.  The !slot case is handled correctly, and
it's the same as before.

- Eric

Re: [PATCH 2/3] blk-crypto: make blk_crypto_evict_key() more robust

[Nathan Huckleberry]

You're right. Nevermind.

Reviewed-by: Nathan Huckleberry <nhuck@google.com>

On Fri, Mar 3, 2023 at 11:50 AM Eric Biggers <ebiggers@kernel.org> wrote:
>
> On Fri, Mar 03, 2023 at 11:45:00AM -0800, Nathan Huckleberry wrote:
> > >  int __blk_crypto_evict_key(struct blk_crypto_profile *profile,
> > >                            const struct blk_crypto_key *key)
> > > @@ -389,22 +377,22 @@ int __blk_crypto_evict_key(struct blk_crypto_profile *profile,
> > >
> > >         blk_crypto_hw_enter(profile);
> > >         slot = blk_crypto_find_keyslot(profile, key);
> > > -       if (!slot)
> > > -               goto out_unlock;
> > > -
> > > -       if (WARN_ON_ONCE(atomic_read(&slot->slot_refs) != 0)) {
> > > -               err = -EBUSY;
> > > -               goto out_unlock;
> > > +       if (slot) {
> > > +               if (WARN_ON_ONCE(atomic_read(&slot->slot_refs) != 0)) {
> > > +                       /* BUG: key is still in use by I/O */
> > > +                       err = -EBUSY;
> > > +               } else {
> > > +                       err = profile->ll_ops.keyslot_evict(
> > > +                                       profile, key,
> > > +                                       blk_crypto_keyslot_index(slot));
> > > +               }
> > > +               /*
> > > +                * Callers may 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;
> > >         }
> >
> > The !slot case still needs to be handled. If profile->num_slots != 0
> > and !slot, we'll get an invalid index from blk_crypto_keyslot_index.
> >
> > With that change,
> > Reviewed-by: Nathan Huckleberry <nhuck@google.com>
> >
> > Thanks,
> > Huck
> >
> > > -       err = profile->ll_ops.keyslot_evict(profile, key,
> > > -                                           blk_crypto_keyslot_index(slot));
> > > -       if (err)
> > > -               goto out_unlock;
> > > -
> > > -       hlist_del(&slot->hash_node);
> > > -       slot->key = NULL;
> > > -       err = 0;
> > > -out_unlock:
> > >         blk_crypto_hw_exit(profile);
> > >         return err;
> > >  }
>
> I'm not sure what you're referring to.  The !slot case is handled correctly, and
> it's the same as before.
>
> - Eric