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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:
parent
7399b886b5
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@ -65,6 +65,11 @@ static inline bool blk_crypto_rq_is_encrypted(struct request *rq)
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return rq->crypt_ctx;
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}
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static inline bool blk_crypto_rq_has_keyslot(struct request *rq)
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{
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return rq->crypt_keyslot;
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}
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blk_status_t blk_crypto_get_keyslot(struct blk_crypto_profile *profile,
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const struct blk_crypto_key *key,
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struct blk_crypto_keyslot **slot_ptr);
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@ -119,6 +124,11 @@ static inline bool blk_crypto_rq_is_encrypted(struct request *rq)
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return false;
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}
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static inline bool blk_crypto_rq_has_keyslot(struct request *rq)
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{
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return false;
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}
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#endif /* CONFIG_BLK_INLINE_ENCRYPTION */
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void __bio_crypt_advance(struct bio *bio, unsigned int bytes);
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@ -153,14 +163,21 @@ static inline bool blk_crypto_bio_prep(struct bio **bio_ptr)
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return true;
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}
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blk_status_t __blk_crypto_init_request(struct request *rq);
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static inline blk_status_t blk_crypto_init_request(struct request *rq)
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blk_status_t __blk_crypto_rq_get_keyslot(struct request *rq);
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static inline blk_status_t blk_crypto_rq_get_keyslot(struct request *rq)
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{
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if (blk_crypto_rq_is_encrypted(rq))
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return __blk_crypto_init_request(rq);
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return __blk_crypto_rq_get_keyslot(rq);
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return BLK_STS_OK;
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}
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void __blk_crypto_rq_put_keyslot(struct request *rq);
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static inline void blk_crypto_rq_put_keyslot(struct request *rq)
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{
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if (blk_crypto_rq_has_keyslot(rq))
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__blk_crypto_rq_put_keyslot(rq);
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}
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void __blk_crypto_free_request(struct request *rq);
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static inline void blk_crypto_free_request(struct request *rq)
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{
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@ -199,7 +216,7 @@ static inline blk_status_t blk_crypto_insert_cloned_request(struct request *rq)
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{
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if (blk_crypto_rq_is_encrypted(rq))
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return blk_crypto_init_request(rq);
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return blk_crypto_rq_get_keyslot(rq);
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return BLK_STS_OK;
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}
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@ -224,27 +224,27 @@ static bool bio_crypt_check_alignment(struct bio *bio)
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return true;
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}
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blk_status_t __blk_crypto_init_request(struct request *rq)
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blk_status_t __blk_crypto_rq_get_keyslot(struct request *rq)
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{
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return blk_crypto_get_keyslot(rq->q->crypto_profile,
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rq->crypt_ctx->bc_key,
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&rq->crypt_keyslot);
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}
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/**
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* __blk_crypto_free_request - Uninitialize the crypto fields of a request.
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*
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* @rq: The request whose crypto fields to uninitialize.
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*
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* Completely uninitializes the crypto fields of a request. If a keyslot has
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* been programmed into some inline encryption hardware, that keyslot is
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* released. The rq->crypt_ctx is also freed.
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*/
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void __blk_crypto_free_request(struct request *rq)
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void __blk_crypto_rq_put_keyslot(struct request *rq)
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{
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blk_crypto_put_keyslot(rq->crypt_keyslot);
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rq->crypt_keyslot = NULL;
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}
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void __blk_crypto_free_request(struct request *rq)
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{
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/* The keyslot, if one was needed, should have been released earlier. */
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if (WARN_ON_ONCE(rq->crypt_keyslot))
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__blk_crypto_rq_put_keyslot(rq);
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mempool_free(rq->crypt_ctx, bio_crypt_ctx_pool);
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blk_crypto_rq_set_defaults(rq);
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rq->crypt_ctx = NULL;
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}
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/**
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@ -867,6 +867,8 @@ static struct request *attempt_merge(struct request_queue *q,
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if (!blk_discard_mergable(req))
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elv_merge_requests(q, req, next);
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blk_crypto_rq_put_keyslot(next);
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/*
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* 'next' is going away, so update stats accordingly
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*/
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@ -840,6 +840,12 @@ static void blk_complete_request(struct request *req)
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req->q->integrity.profile->complete_fn(req, total_bytes);
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#endif
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/*
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* Upper layers may call blk_crypto_evict_key() anytime after the last
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* bio_endio(). Therefore, the keyslot must be released before that.
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*/
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blk_crypto_rq_put_keyslot(req);
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blk_account_io_completion(req, total_bytes);
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do {
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@ -905,6 +911,13 @@ bool blk_update_request(struct request *req, blk_status_t error,
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req->q->integrity.profile->complete_fn(req, nr_bytes);
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#endif
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/*
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* Upper layers may call blk_crypto_evict_key() anytime after the last
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* bio_endio(). Therefore, the keyslot must be released before that.
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*/
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if (blk_crypto_rq_has_keyslot(req) && nr_bytes >= blk_rq_bytes(req))
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__blk_crypto_rq_put_keyslot(req);
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if (unlikely(error && !blk_rq_is_passthrough(req) &&
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!(req->rq_flags & RQF_QUIET)) &&
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!test_bit(GD_DEAD, &req->q->disk->state)) {
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@ -2967,7 +2980,7 @@ void blk_mq_submit_bio(struct bio *bio)
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blk_mq_bio_to_request(rq, bio, nr_segs);
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ret = blk_crypto_init_request(rq);
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ret = blk_crypto_rq_get_keyslot(rq);
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if (ret != BLK_STS_OK) {
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bio->bi_status = ret;
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bio_endio(bio);
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