Encrypting a large bio with more than BIO_MAX_VECS pages can still deadlock, even after it was attempted to be fixed by commit b37fbce460ad ("blk-crypto: optimize bio splitting in blk_crypto_fallback_encrypt_bio") and commit 3d939695e682 ("blk-crypto: use mempool_alloc_bulk for encrypted bio page allocation"). This is because __blk_crypto_fallback_encrypt_bio() assumes that the bounce bios that it submits will eventually complete, unblocking it from allocating additional bounce bios and pages. However, dm-inlinecrypt.c calls __blk_crypto_submit_bio() from within submit_bio() itself. In this case, the recursive submit_bio() simply adds the bounce bio to current->bio_list without actually submitting it yet. That breaks the guarantee that forward progress is being made. To fix this, allocate the bio and bounce pages with GFP_NOWAIT if current->bio_list is set. If it fails, punt the encryption of the remaining part of the bio to a kworker. Fixes: 488f6682c832 ("block: blk-crypto-fallback for Inline Encryption") Cc: stable@vger.kernel.org Signed-off-by: Eric Biggers --- Changed in v2: - Switched to the less efficient approach preferred by Christoph - Use BIO_EMPTY_LIST block/blk-crypto-fallback.c | 80 ++++++++++++++++++++++++++++++++++--- 1 file changed, 75 insertions(+), 5 deletions(-) diff --git a/block/blk-crypto-fallback.c b/block/blk-crypto-fallback.c index 2a5c52ab74b4..ad4b5ca291c5 100644 --- a/block/blk-crypto-fallback.c +++ b/block/blk-crypto-fallback.c @@ -83,6 +83,10 @@ static struct workqueue_struct *blk_crypto_wq; static mempool_t *blk_crypto_bounce_page_pool; static struct bio_set enc_bio_set; +static DEFINE_SPINLOCK(enc_rescue_list_lock); +static struct bio_list enc_rescue_list = BIO_EMPTY_LIST; +static struct work_struct enc_rescue_work; + /* * This is the key we set when evicting a keyslot. This *should* be the all 0's * key, but AES-XTS rejects that key, so we use some random bytes instead. @@ -172,13 +176,26 @@ static void blk_crypto_fallback_encrypt_endio(struct bio *enc_bio) static struct bio *blk_crypto_alloc_enc_bio(struct bio *bio_src, unsigned int nr_segs, struct page ***pages_ret) { - unsigned int memflags = memalloc_noio_save(); unsigned int nr_allocated; struct page **pages; struct bio *bio; + gfp_t gfp_mask; + + /* + * During recursive bio submission (current->bio_list != NULL) any + * submitted bounce bios just get added to current->bio_list; they + * cannot complete and release resources yet. Therefore, to avoid + * deadlocks, don't wait indefinitely for additional resources. + */ + if (current->bio_list) + gfp_mask = GFP_NOWAIT; + else + gfp_mask = GFP_NOIO; bio = bio_alloc_bioset(bio_src->bi_bdev, nr_segs, bio_src->bi_opf, - GFP_NOIO, &enc_bio_set); + gfp_mask, &enc_bio_set); + if (unlikely(!bio)) + return NULL; /* GFP_NOWAIT failure. Fall back to kworker. */ if (bio_flagged(bio_src, BIO_REMAPPED)) bio_set_flag(bio, BIO_REMAPPED); bio->bi_private = bio_src; @@ -206,12 +223,27 @@ static struct bio *blk_crypto_alloc_enc_bio(struct bio *bio_src, * any non-zero slot already contains a valid allocation. */ memset(pages, 0, sizeof(struct page *) * nr_segs); - nr_allocated = alloc_pages_bulk(GFP_KERNEL, nr_segs, pages); - if (nr_allocated < nr_segs) + nr_allocated = alloc_pages_bulk(gfp_mask, nr_segs, pages); + if (unlikely(nr_allocated < nr_segs)) { + unsigned int memflags; + + if (!(gfp_mask & __GFP_DIRECT_RECLAIM)) { + /* + * GFP_NOWAIT failure. Fall back to kworker, even if + * enough pages are already free in the mempool (since + * mempool_alloc_bulk() doesn't have a no-wait mode). + */ + free_pages_bulk(pages, nr_allocated); + bio_put(bio); + return NULL; + } + + memflags = memalloc_noio_save(); mempool_alloc_bulk(blk_crypto_bounce_page_pool, (void **)pages + nr_allocated, nr_segs - nr_allocated); - memalloc_noio_restore(memflags); + memalloc_noio_restore(memflags); + } *pages_ret = pages; return bio; } @@ -239,6 +271,25 @@ static void blk_crypto_dun_to_iv(const u64 dun[BLK_CRYPTO_DUN_ARRAY_SIZE], iv->dun[i] = cpu_to_le64(dun[i]); } +static void blk_crypto_fallback_encrypt_bio(struct bio *src_bio); + +/* Encrypt a list of bios whose encryption was punted to a kworker. */ +static void blk_crypto_fallback_encrypt_work_fn(struct work_struct *work) +{ + struct bio_list list; + struct bio *src_bio; + + WARN_ON_ONCE(current->bio_list); + + spin_lock(&enc_rescue_list_lock); + list = enc_rescue_list; + bio_list_init(&enc_rescue_list); + spin_unlock(&enc_rescue_list_lock); + + while ((src_bio = bio_list_pop(&list))) + blk_crypto_fallback_encrypt_bio(src_bio); +} + static void __blk_crypto_fallback_encrypt_bio(struct bio *src_bio, struct crypto_sync_skcipher *tfm) { @@ -273,6 +324,23 @@ static void __blk_crypto_fallback_encrypt_bio(struct bio *src_bio, new_bio: nr_enc_pages = min(bio_segments(src_bio), BIO_MAX_VECS); enc_bio = blk_crypto_alloc_enc_bio(src_bio, nr_enc_pages, &enc_pages); + if (unlikely(!enc_bio)) { + /* + * Failed to allocate a bounce bio during recursive bio + * submission. We might be blocked on bios in current->bio_list + * holding mempool elements. To enable forward progress, punt + * the remaining encryption work for src_bio to a kworker. + * + * The DUN may have been advanced, so make sure to update it. + */ + WARN_ON_ONCE(!current->bio_list); + memcpy(bc->bc_dun, curr_dun, sizeof(curr_dun)); + spin_lock(&enc_rescue_list_lock); + bio_list_add(&enc_rescue_list, src_bio); + spin_unlock(&enc_rescue_list_lock); + queue_work(blk_crypto_wq, &enc_rescue_work); + return; + } enc_idx = 0; for (;;) { struct bio_vec src_bv = @@ -591,6 +659,8 @@ static int blk_crypto_fallback_init(void) if (!bio_fallback_crypt_ctx_pool) goto fail_free_crypt_ctx_cache; + INIT_WORK(&enc_rescue_work, blk_crypto_fallback_encrypt_work_fn); + blk_crypto_fallback_inited = true; return 0; base-commit: db2ddb87143519e20a95aa36c60b36107b736a58 -- 2.55.0