On Tue, Sep 15, 2020 at 08:53:14PM -0700, Eric Biggers wrote:
> From: Eric Biggers <ebiggers@xxxxxxxxxx>
>
> blk_crypto_rq_bio_prep() assumes its gfp_mask argument always includes
> __GFP_DIRECT_RECLAIM, so that the mempool_alloc() will always succeed.
>
> However, blk_crypto_rq_bio_prep() might be called with GFP_ATOMIC via
> setup_clone() in drivers/md/dm-rq.c.
>
> This case isn't currently reachable with a bio that actually has an
> encryption context. However, it's fragile to rely on this. Just make
> blk_crypto_rq_bio_prep() able to fail.
>
> Cc: Miaohe Lin <linmiaohe@xxxxxxxxxx>
> Suggested-by: Satya Tangirala <satyat@xxxxxxxxxx>
> Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx>
> ---
> block/blk-core.c | 8 +++++---
> block/blk-crypto-internal.h | 21 ++++++++++++++++-----
> block/blk-crypto.c | 18 +++++++-----------
> block/blk-mq.c | 7 ++++++-
> 4 files changed, 34 insertions(+), 20 deletions(-)
>
> diff --git a/block/blk-core.c b/block/blk-core.c
> index ca3f0f00c9435..fbeaa49f6fe2c 100644
> --- a/block/blk-core.c
> +++ b/block/blk-core.c
> @@ -1620,8 +1620,10 @@ int blk_rq_prep_clone(struct request *rq, struct request *rq_src,
> if (rq->bio) {
> rq->biotail->bi_next = bio;
> rq->biotail = bio;
> - } else
> + } else {
> rq->bio = rq->biotail = bio;
> + }
> + bio = NULL;
> }
>
> /* Copy attributes of the original request to the clone request. */
> @@ -1634,8 +1636,8 @@ int blk_rq_prep_clone(struct request *rq, struct request *rq_src,
> rq->nr_phys_segments = rq_src->nr_phys_segments;
> rq->ioprio = rq_src->ioprio;
>
> - if (rq->bio)
> - blk_crypto_rq_bio_prep(rq, rq->bio, gfp_mask);
> + if (rq->bio && blk_crypto_rq_bio_prep(rq, rq->bio, gfp_mask) < 0)
> + goto free_and_out;
>
> return 0;
>
> diff --git a/block/blk-crypto-internal.h b/block/blk-crypto-internal.h
> index d2b0f565d83cb..0d36aae538d7b 100644
> --- a/block/blk-crypto-internal.h
> +++ b/block/blk-crypto-internal.h
> @@ -142,13 +142,24 @@ static inline void blk_crypto_free_request(struct request *rq)
> __blk_crypto_free_request(rq);
> }
>
> -void __blk_crypto_rq_bio_prep(struct request *rq, struct bio *bio,
> - gfp_t gfp_mask);
> -static inline void blk_crypto_rq_bio_prep(struct request *rq, struct bio *bio,
> - gfp_t gfp_mask)
> +int __blk_crypto_rq_bio_prep(struct request *rq, struct bio *bio,
> + gfp_t gfp_mask);
> +/**
> + * blk_crypto_rq_bio_prep - Prepare a request's crypt_ctx when its first bio
> + * is inserted
> + * @rq: The request to prepare
> + * @bio: The first bio being inserted into the request
> + * @gfp_mask: Memory allocation flags
> + *
> + * Return: 0 on success, -ENOMEM if out of memory. -ENOMEM is only possible if
> + * @gfp_mask doesn't include %__GFP_DIRECT_RECLAIM.
> + */
> +static inline int blk_crypto_rq_bio_prep(struct request *rq, struct bio *bio,
> + gfp_t gfp_mask)
> {
> if (bio_has_crypt_ctx(bio))
> - __blk_crypto_rq_bio_prep(rq, bio, gfp_mask);
> + return __blk_crypto_rq_bio_prep(rq, bio, gfp_mask);
> + return 0;
> }
>
> /**
> diff --git a/block/blk-crypto.c b/block/blk-crypto.c
> index a3f27a19067c9..bbe7974fd74f0 100644
> --- a/block/blk-crypto.c
> +++ b/block/blk-crypto.c
> @@ -283,20 +283,16 @@ bool __blk_crypto_bio_prep(struct bio **bio_ptr)
> return false;
> }
>
> -/**
> - * __blk_crypto_rq_bio_prep - Prepare a request's crypt_ctx when its first bio
> - * is inserted
> - *
> - * @rq: The request to prepare
> - * @bio: The first bio being inserted into the request
> - * @gfp_mask: gfp mask
> - */
> -void __blk_crypto_rq_bio_prep(struct request *rq, struct bio *bio,
> - gfp_t gfp_mask)
> +int __blk_crypto_rq_bio_prep(struct request *rq, struct bio *bio,
> + gfp_t gfp_mask)
> {
> - if (!rq->crypt_ctx)
> + if (!rq->crypt_ctx) {
> rq->crypt_ctx = mempool_alloc(bio_crypt_ctx_pool, gfp_mask);
> + if (!rq->crypt_ctx)
> + return -ENOMEM;
> + }
> *rq->crypt_ctx = *bio->bi_crypt_context;
> + return 0;
> }
>
> /**
> diff --git a/block/blk-mq.c b/block/blk-mq.c
> index e04b759add758..9ec0e7149ae69 100644
> --- a/block/blk-mq.c
> +++ b/block/blk-mq.c
> @@ -1940,13 +1940,18 @@ void blk_mq_flush_plug_list(struct blk_plug *plug, bool from_schedule)
> static void blk_mq_bio_to_request(struct request *rq, struct bio *bio,
> unsigned int nr_segs)
> {
> + int err;
> +
> if (bio->bi_opf & REQ_RAHEAD)
> rq->cmd_flags |= REQ_FAILFAST_MASK;
>
> rq->__sector = bio->bi_iter.bi_sector;
> rq->write_hint = bio->bi_write_hint;
> blk_rq_bio_prep(rq, bio, nr_segs);
> - blk_crypto_rq_bio_prep(rq, bio, GFP_NOIO);
> +
> + /* This can't fail, since GFP_NOIO includes __GFP_DIRECT_RECLAIM. */
> + err = blk_crypto_rq_bio_prep(rq, bio, GFP_NOIO);
> + WARN_ON_ONCE(err);
>
> blk_account_io_start(rq);
> }
Looks good!
Reviewed-by: Satya Tangirala <satyat@xxxxxxxxxx>
> --
> 2.28.0
>
