Commit 9cd1e566 authored by Eric Biggers's avatar Eric Biggers Committed by Jens Axboe
Browse files

blk-mq: release crypto keyslot before reporting I/O complete 



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: a892c8d5 ("block: Inline encryption support for blk-mq")
Cc: stable@vger.kernel.org
Reviewed-by: default avatarNathan Huckleberry <nhuck@google.com>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarEric Biggers <ebiggers@google.com>
Link: https://lore.kernel.org/r/20230315183907.53675-2-ebiggers@kernel.org


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 7399b886

block/blk-crypto-internal.h

+21 −4
Original line number Original line Diff line number Diff line
@@ -65,6 +65,11 @@ static inline bool blk_crypto_rq_is_encrypted(struct request *rq) 
	return rq->crypt_ctx;

	return rq->crypt_ctx;

}

}





static inline bool blk_crypto_rq_has_keyslot(struct request *rq)

{

	return rq->crypt_keyslot;

}



blk_status_t blk_crypto_get_keyslot(struct blk_crypto_profile *profile,

blk_status_t blk_crypto_get_keyslot(struct blk_crypto_profile *profile,

				    const struct blk_crypto_key *key,

				    const struct blk_crypto_key *key,

				    struct blk_crypto_keyslot **slot_ptr);

				    struct blk_crypto_keyslot **slot_ptr);
@@ -119,6 +124,11 @@ static inline bool blk_crypto_rq_is_encrypted(struct request *rq) 
	return false;

	return false;

}

}





static inline bool blk_crypto_rq_has_keyslot(struct request *rq)

{

	return false;

}



#endif /* CONFIG_BLK_INLINE_ENCRYPTION */

#endif /* CONFIG_BLK_INLINE_ENCRYPTION */





void __bio_crypt_advance(struct bio *bio, unsigned int bytes);

void __bio_crypt_advance(struct bio *bio, unsigned int bytes);
@@ -153,14 +163,21 @@ static inline bool blk_crypto_bio_prep(struct bio **bio_ptr) 
	return true;

	return true;

}

}





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_init_request(struct request *rq)

static inline blk_status_t blk_crypto_rq_get_keyslot(struct request *rq)

{

{

	if (blk_crypto_rq_is_encrypted(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;

	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);

void __blk_crypto_free_request(struct request *rq);

static inline void blk_crypto_free_request(struct request *rq)

static inline void blk_crypto_free_request(struct request *rq)

{

{
@@ -199,7 +216,7 @@ static inline blk_status_t blk_crypto_insert_cloned_request(struct request *rq) 
{

{





	if (blk_crypto_rq_is_encrypted(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;

	return BLK_STS_OK;

}

}

block/blk-crypto.c

+12 −12
Original line number Original line Diff line number Diff line
@@ -224,27 +224,27 @@ static bool bio_crypt_check_alignment(struct bio *bio) 
	return true;

	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,

	return blk_crypto_get_keyslot(rq->q->crypto_profile,

				      rq->crypt_ctx->bc_key,

				      rq->crypt_ctx->bc_key,

				      &rq->crypt_keyslot);

				      &rq->crypt_keyslot);

}

}





/**

void __blk_crypto_rq_put_keyslot(struct request *rq)

 * __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)

{

{

	blk_crypto_put_keyslot(rq->crypt_keyslot);

	blk_crypto_put_keyslot(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);

	mempool_free(rq->crypt_ctx, bio_crypt_ctx_pool);

	blk_crypto_rq_set_defaults(rq);

	rq->crypt_ctx = NULL;

}

}





/**

/**

block/blk-merge.c

+2 −0
Original line number Original line Diff line number Diff line
@@ -867,6 +867,8 @@ static struct request *attempt_merge(struct request_queue *q, 
	if (!blk_discard_mergable(req))

	if (!blk_discard_mergable(req))

		elv_merge_requests(q, req, next);

		elv_merge_requests(q, req, next);





	blk_crypto_rq_put_keyslot(next);



	/*

	/*

	 * 'next' is going away, so update stats accordingly

	 * 'next' is going away, so update stats accordingly

	 */

	 */

block/blk-mq.c

+14 −1
Original line number Original line Diff line number Diff line
@@ -840,6 +840,12 @@ static void blk_complete_request(struct request *req) 
		req->q->integrity.profile->complete_fn(req, total_bytes);

		req->q->integrity.profile->complete_fn(req, total_bytes);

#endif

#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);

	blk_account_io_completion(req, total_bytes);





	do {

	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);

		req->q->integrity.profile->complete_fn(req, nr_bytes);

#endif

#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) &&

	if (unlikely(error && !blk_rq_is_passthrough(req) &&

		     !(req->rq_flags & RQF_QUIET)) &&

		     !(req->rq_flags & RQF_QUIET)) &&

		     !test_bit(GD_DEAD, &req->q->disk->state)) {

		     !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);

	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) {

	if (ret != BLK_STS_OK) {

		bio->bi_status = ret;

		bio->bi_status = ret;

		bio_endio(bio);

		bio_endio(bio);