block: make bio_crypt_clone() able to fail

bio_crypt_clone() assumes its gfp_mask argument always includes
__GFP_DIRECT_RECLAIM, so that the mempool_alloc() will always succeed.

However, bio_crypt_clone() might be called with GFP_ATOMIC via
setup_clone() in drivers/md/dm-rq.c, or with GFP_NOWAIT via
kcryptd_io_read() in drivers/md/dm-crypt.c.

Neither case is currently reachable with a bio that actually has an
encryption context.  However, it's fragile to rely on this.  Just make
bio_crypt_clone() able to fail, analogous to bio_integrity_clone().
Reported-by: Miaohe Lin <linmiaohe@huawei.com>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Reviewed-by: Mike Snitzer <snitzer@redhat.com>
Reviewed-by: Satya Tangirala <satyat@google.com>
Cc: Satya Tangirala <satyat@google.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block/bio.c

@@ -713,20 +713,18 @@ struct bio *bio_clone_fast(struct bio *bio, gfp_t gfp_mask, struct bio_set *bs)
 
 	__bio_clone_fast(b, bio);
 
-	bio_crypt_clone(b, bio, gfp_mask);
+	if (bio_crypt_clone(b, bio, gfp_mask) < 0)
+		goto err_put;
 
-	if (bio_integrity(bio)) {
-		int ret;
+	if (bio_integrity(bio) &&
+	    bio_integrity_clone(b, bio, gfp_mask) < 0)
+		goto err_put;
 
-		ret = bio_integrity_clone(b, bio, gfp_mask);
+	return b;
 
-		if (ret < 0) {
+err_put:
 	bio_put(b);
 	return NULL;
-		}
-	}
-
-	return b;
 }
 EXPORT_SYMBOL(bio_clone_fast);
 

block/blk-crypto.c

@@ -95,10 +95,13 @@ void __bio_crypt_free_ctx(struct bio *bio)
 	bio->bi_crypt_context = NULL;
 }
 
-void __bio_crypt_clone(struct bio *dst, struct bio *src, gfp_t gfp_mask)
+int __bio_crypt_clone(struct bio *dst, struct bio *src, gfp_t gfp_mask)
 {
 	dst->bi_crypt_context = mempool_alloc(bio_crypt_ctx_pool, gfp_mask);
+	if (!dst->bi_crypt_context)
+		return -ENOMEM;
 	*dst->bi_crypt_context = *src->bi_crypt_context;
+	return 0;
 }
 EXPORT_SYMBOL_GPL(__bio_crypt_clone);
 

block/bounce.c

@@ -267,22 +267,21 @@ static struct bio *bounce_clone_bio(struct bio *bio_src, gfp_t gfp_mask,
 		break;
 	}
 
-	bio_crypt_clone(bio, bio_src, gfp_mask);
+	if (bio_crypt_clone(bio, bio_src, gfp_mask) < 0)
+		goto err_put;
 
-	if (bio_integrity(bio_src)) {
-		int ret;
-
-		ret = bio_integrity_clone(bio, bio_src, gfp_mask);
-		if (ret < 0) {
-			bio_put(bio);
-			return NULL;
-		}
-	}
+	if (bio_integrity(bio_src) &&
+	    bio_integrity_clone(bio, bio_src, gfp_mask) < 0)
+		goto err_put;
 
 	bio_clone_blkg_association(bio, bio_src);
 	blkcg_bio_issue_init(bio);
 
 	return bio;
+
+err_put:
+	bio_put(bio);
+	return NULL;
 }
 
 static void __blk_queue_bounce(struct request_queue *q, struct bio **bio_orig,

drivers/md/dm.c

@@ -1326,14 +1326,15 @@ static int clone_bio(struct dm_target_io *tio, struct bio *bio,
 		     sector_t sector, unsigned len)
 {
 	struct bio *clone = &tio->clone;
+	int r;
 
 	__bio_clone_fast(clone, bio);
 
-	bio_crypt_clone(clone, bio, GFP_NOIO);
+	r = bio_crypt_clone(clone, bio, GFP_NOIO);
+	if (r < 0)
+		return r;
 
 	if (bio_integrity(bio)) {
-		int r;
-
 		if (unlikely(!dm_target_has_integrity(tio->ti->type) &&
 			     !dm_target_passes_integrity(tio->ti->type))) {
 			DMWARN("%s: the target %s doesn't support integrity data.",

include/linux/blk-crypto.h

@@ -112,12 +112,24 @@ static inline bool bio_has_crypt_ctx(struct bio *bio)
 
 #endif /* CONFIG_BLK_INLINE_ENCRYPTION */
 
-void __bio_crypt_clone(struct bio *dst, struct bio *src, gfp_t gfp_mask);
-static inline void bio_crypt_clone(struct bio *dst, struct bio *src,
+int __bio_crypt_clone(struct bio *dst, struct bio *src, gfp_t gfp_mask);
+/**
+ * bio_crypt_clone - clone bio encryption context
+ * @dst: destination bio
+ * @src: source bio
+ * @gfp_mask: memory allocation flags
+ *
+ * If @src has an encryption context, clone it to @dst.
+ *
+ * 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 bio_crypt_clone(struct bio *dst, struct bio *src,
 				  gfp_t gfp_mask)
 {
 	if (bio_has_crypt_ctx(src))
-		__bio_crypt_clone(dst, src, gfp_mask);
+		return __bio_crypt_clone(dst, src, gfp_mask);
+	return 0;
 }
 
 #endif /* __LINUX_BLK_CRYPTO_H */