* [PATCH 0/3] Fix blk-crypto keyslot race condition
@ 2023-03-03 7:19 Eric Biggers
2023-03-03 7:19 ` [PATCH 1/3] blk-mq: release crypto keyslot before reporting I/O complete Eric Biggers
` (2 more replies)
0 siblings, 3 replies; 9+ messages in thread
From: Eric Biggers @ 2023-03-03 7:19 UTC (permalink / raw)
To: linux-block, Jens Axboe; +Cc: linux-fscrypt, Nathan Huckleberry
This series fixes a race condition in blk-crypto keyslot management and
makes some related cleanups. It replaces
"[PATCH] blk-crypto: make blk_crypto_evict_key() always try to evict"
(https://lore.kernel.org/r/20230226203816.207449-1-ebiggers@kernel.org),
which was a simpler fix but didn't fix the keyslot reference counting to
work as expected.
Eric Biggers (3):
blk-mq: release crypto keyslot before reporting I/O complete
blk-crypto: make blk_crypto_evict_key() more robust
blk-crypto: remove blk_crypto_insert_cloned_request()
Documentation/block/inline-encryption.rst | 3 +-
block/blk-crypto-internal.h | 28 +++++--------
block/blk-crypto-profile.c | 50 +++++++++--------------
block/blk-crypto.c | 47 +++++++++++----------
block/blk-mq.c | 17 +++++++-
5 files changed, 71 insertions(+), 74 deletions(-)
base-commit: 2eb29d59ddf02e39774abfb60b2030b0b7e27c1f
--
2.39.2
^ permalink raw reply [flat|nested] 9+ messages in thread
* [PATCH 1/3] blk-mq: release crypto keyslot before reporting I/O complete
2023-03-03 7:19 [PATCH 0/3] Fix blk-crypto keyslot race condition Eric Biggers
@ 2023-03-03 7:19 ` Eric Biggers
2023-03-03 19:29 ` Nathan Huckleberry
2023-03-08 18:21 ` Eric Biggers
2023-03-03 7:19 ` [PATCH 2/3] blk-crypto: make blk_crypto_evict_key() more robust Eric Biggers
2023-03-03 7:19 ` [PATCH 3/3] blk-crypto: remove blk_crypto_insert_cloned_request() Eric Biggers
2 siblings, 2 replies; 9+ messages in thread
From: Eric Biggers @ 2023-03-03 7:19 UTC (permalink / raw)
To: linux-block, Jens Axboe; +Cc: linux-fscrypt, Nathan Huckleberry, stable
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
^ permalink raw reply related [flat|nested] 9+ messages in thread
* [PATCH 2/3] blk-crypto: make blk_crypto_evict_key() more robust
2023-03-03 7:19 [PATCH 0/3] Fix blk-crypto keyslot race condition Eric Biggers
2023-03-03 7:19 ` [PATCH 1/3] blk-mq: release crypto keyslot before reporting I/O complete Eric Biggers
@ 2023-03-03 7:19 ` Eric Biggers
2023-03-03 19:45 ` Nathan Huckleberry
2023-03-03 7:19 ` [PATCH 3/3] blk-crypto: remove blk_crypto_insert_cloned_request() Eric Biggers
2 siblings, 1 reply; 9+ messages in thread
From: Eric Biggers @ 2023-03-03 7:19 UTC (permalink / raw)
To: linux-block, Jens Axboe; +Cc: linux-fscrypt, Nathan Huckleberry, stable
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
^ permalink raw reply related [flat|nested] 9+ messages in thread
* [PATCH 3/3] blk-crypto: remove blk_crypto_insert_cloned_request()
2023-03-03 7:19 [PATCH 0/3] Fix blk-crypto keyslot race condition Eric Biggers
2023-03-03 7:19 ` [PATCH 1/3] blk-mq: release crypto keyslot before reporting I/O complete Eric Biggers
2023-03-03 7:19 ` [PATCH 2/3] blk-crypto: make blk_crypto_evict_key() more robust Eric Biggers
@ 2023-03-03 7:19 ` Eric Biggers
2 siblings, 0 replies; 9+ messages in thread
From: Eric Biggers @ 2023-03-03 7:19 UTC (permalink / raw)
To: linux-block, Jens Axboe; +Cc: linux-fscrypt, Nathan Huckleberry
From: Eric Biggers <ebiggers@google.com>
blk_crypto_insert_cloned_request() is the same as
blk_crypto_rq_get_keyslot(), so just use that directly.
Signed-off-by: Eric Biggers <ebiggers@google.com>
---
Documentation/block/inline-encryption.rst | 3 +--
block/blk-crypto-internal.h | 15 ---------------
block/blk-mq.c | 2 +-
3 files changed, 2 insertions(+), 18 deletions(-)
diff --git a/Documentation/block/inline-encryption.rst b/Documentation/block/inline-encryption.rst
index f9bf18ea65093..90b733422ed46 100644
--- a/Documentation/block/inline-encryption.rst
+++ b/Documentation/block/inline-encryption.rst
@@ -270,8 +270,7 @@ Request queue based layered devices like dm-rq that wish to support inline
encryption need to create their own blk_crypto_profile for their request_queue,
and expose whatever functionality they choose. When a layered device wants to
pass a clone of that request to another request_queue, blk-crypto will
-initialize and prepare the clone as necessary; see
-``blk_crypto_insert_cloned_request()``.
+initialize and prepare the clone as necessary.
Interaction between inline encryption and blk integrity
=======================================================
diff --git a/block/blk-crypto-internal.h b/block/blk-crypto-internal.h
index 73609902349b6..0f55e5b4bbbf2 100644
--- a/block/blk-crypto-internal.h
+++ b/block/blk-crypto-internal.h
@@ -195,21 +195,6 @@ static inline int blk_crypto_rq_bio_prep(struct request *rq, struct bio *bio,
return 0;
}
-/**
- * blk_crypto_insert_cloned_request - Prepare a cloned request to be inserted
- * into a request queue.
- * @rq: the request being queued
- *
- * Return: BLK_STS_OK on success, nonzero on error.
- */
-static inline blk_status_t blk_crypto_insert_cloned_request(struct request *rq)
-{
-
- if (blk_crypto_rq_is_encrypted(rq))
- return blk_crypto_rq_get_keyslot(rq);
- return BLK_STS_OK;
-}
-
#ifdef CONFIG_BLK_INLINE_ENCRYPTION_FALLBACK
int blk_crypto_fallback_start_using_mode(enum blk_crypto_mode_num mode_num);
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 738e81f518227..61ed699e89d53 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -3048,7 +3048,7 @@ blk_status_t blk_insert_cloned_request(struct request *rq)
if (q->disk && should_fail_request(q->disk->part0, blk_rq_bytes(rq)))
return BLK_STS_IOERR;
- if (blk_crypto_insert_cloned_request(rq))
+ if (blk_crypto_rq_get_keyslot(rq))
return BLK_STS_IOERR;
blk_account_io_start(rq);
--
2.39.2
^ permalink raw reply related [flat|nested] 9+ messages in thread
* Re: [PATCH 1/3] blk-mq: release crypto keyslot before reporting I/O complete
2023-03-03 7:19 ` [PATCH 1/3] blk-mq: release crypto keyslot before reporting I/O complete Eric Biggers
@ 2023-03-03 19:29 ` Nathan Huckleberry
2023-03-08 18:21 ` Eric Biggers
1 sibling, 0 replies; 9+ messages in thread
From: Nathan Huckleberry @ 2023-03-03 19:29 UTC (permalink / raw)
To: Eric Biggers; +Cc: linux-block, Jens Axboe, linux-fscrypt, stable
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
^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [PATCH 2/3] blk-crypto: make blk_crypto_evict_key() more robust
2023-03-03 7:19 ` [PATCH 2/3] blk-crypto: make blk_crypto_evict_key() more robust Eric Biggers
@ 2023-03-03 19:45 ` Nathan Huckleberry
2023-03-03 19:50 ` Eric Biggers
0 siblings, 1 reply; 9+ messages in thread
From: Nathan Huckleberry @ 2023-03-03 19:45 UTC (permalink / raw)
To: Eric Biggers; +Cc: linux-block, Jens Axboe, linux-fscrypt, stable
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
>
^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [PATCH 2/3] blk-crypto: make blk_crypto_evict_key() more robust
2023-03-03 19:45 ` Nathan Huckleberry
@ 2023-03-03 19:50 ` Eric Biggers
2023-03-03 20:30 ` Nathan Huckleberry
0 siblings, 1 reply; 9+ messages in thread
From: Eric Biggers @ 2023-03-03 19:50 UTC (permalink / raw)
To: Nathan Huckleberry; +Cc: linux-block, Jens Axboe, linux-fscrypt, stable
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
^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [PATCH 2/3] blk-crypto: make blk_crypto_evict_key() more robust
2023-03-03 19:50 ` Eric Biggers
@ 2023-03-03 20:30 ` Nathan Huckleberry
0 siblings, 0 replies; 9+ messages in thread
From: Nathan Huckleberry @ 2023-03-03 20:30 UTC (permalink / raw)
To: Eric Biggers; +Cc: linux-block, Jens Axboe, linux-fscrypt, stable
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
^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [PATCH 1/3] blk-mq: release crypto keyslot before reporting I/O complete
2023-03-03 7:19 ` [PATCH 1/3] blk-mq: release crypto keyslot before reporting I/O complete Eric Biggers
2023-03-03 19:29 ` Nathan Huckleberry
@ 2023-03-08 18:21 ` Eric Biggers
1 sibling, 0 replies; 9+ messages in thread
From: Eric Biggers @ 2023-03-08 18:21 UTC (permalink / raw)
To: linux-block, Jens Axboe; +Cc: linux-fscrypt, Nathan Huckleberry, stable
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
^ permalink raw reply [flat|nested] 9+ messages in thread
end of thread, other threads:[~2023-03-08 18:22 UTC | newest]
Thread overview: 9+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2023-03-03 7:19 [PATCH 0/3] Fix blk-crypto keyslot race condition Eric Biggers
2023-03-03 7:19 ` [PATCH 1/3] blk-mq: release crypto keyslot before reporting I/O complete Eric Biggers
2023-03-03 19:29 ` Nathan Huckleberry
2023-03-08 18:21 ` Eric Biggers
2023-03-03 7:19 ` [PATCH 2/3] blk-crypto: make blk_crypto_evict_key() more robust Eric Biggers
2023-03-03 19:45 ` Nathan Huckleberry
2023-03-03 19:50 ` Eric Biggers
2023-03-03 20:30 ` Nathan Huckleberry
2023-03-03 7:19 ` [PATCH 3/3] blk-crypto: remove blk_crypto_insert_cloned_request() Eric Biggers
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