This is a note to let you know that I've just added the patch titled
blk-mq: release crypto keyslot before reporting I/O complete
to the 5.10-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
blk-mq-release-crypto-keyslot-before-reporting-i-o-complete.patch
and it can be found in the queue-5.10 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From stable-owner@xxxxxxxxxxxxxxx Thu May 4 13:10:13 2023
From: Eric Biggers <ebiggers@xxxxxxxxxx>
Date: Wed, 3 May 2023 21:09:39 -0700
Subject: blk-mq: release crypto keyslot before reporting I/O complete
To: stable@xxxxxxxxxxxxxxx
Cc: linux-block@xxxxxxxxxxxxxxx, Nathan Huckleberry <nhuck@xxxxxxxxxx>, Christoph Hellwig <hch@xxxxxx>, Jens Axboe <axboe@xxxxxxxxx>
Message-ID: <20230504040941.152614-2-ebiggers@xxxxxxxxxx>
From: Eric Biggers <ebiggers@xxxxxxxxxx>
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@xxxxxxxxxxxxxxx
Reviewed-by: Nathan Huckleberry <nhuck@xxxxxxxxxx>
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20230315183907.53675-2-ebiggers@xxxxxxxxxx
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
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(-)
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -1444,6 +1444,13 @@ bool blk_update_request(struct request *
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__);
--- a/block/blk-crypto-internal.h
+++ b/block/blk-crypto-internal.h
@@ -60,6 +60,11 @@ static inline bool blk_crypto_rq_is_encr
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_encr
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(s
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_in
{
if (blk_crypto_rq_is_encrypted(rq))
- return blk_crypto_init_request(rq);
+ return blk_crypto_rq_get_keyslot(rq);
return BLK_STS_OK;
}
--- a/block/blk-crypto.c
+++ b/block/blk-crypto.c
@@ -216,26 +216,26 @@ static bool bio_crypt_check_alignment(st
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;
}
/**
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -801,6 +801,8 @@ static struct request *attempt_merge(str
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
*/
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2193,7 +2193,7 @@ blk_qc_t blk_mq_submit_bio(struct bio *b
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);
Patches currently in stable-queue which might be from stable-owner@xxxxxxxxxxxxxxx are
queue-5.10/blk-crypto-make-blk_crypto_evict_key-more-robust.patch
queue-5.10/blk-mq-release-crypto-keyslot-before-reporting-i-o-complete.patch
queue-5.10/blk-crypto-make-blk_crypto_evict_key-return-void.patch
