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: a892c8d52c ("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>
This commit is contained in:
Eric Biggers 2023-03-15 11:39:02 -07:00 committed by Jens Axboe
parent 7399b886b5
commit 9cd1e56667
4 changed files with 49 additions and 17 deletions

View File

@ -65,6 +65,11 @@ 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;
}
blk_status_t blk_crypto_get_keyslot(struct blk_crypto_profile *profile,
const struct blk_crypto_key *key,
struct blk_crypto_keyslot **slot_ptr);
@ -119,6 +124,11 @@ 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);
@ -153,14 +163,21 @@ 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)
{
@ -199,7 +216,7 @@ 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;
}

View File

@ -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)
{
/* 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;
}
/**

View File

@ -867,6 +867,8 @@ 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
*/

View File

@ -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_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)) &&
!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);