[PATCH v3] nvme: fix metadata handling in nvme-passthrough

[Puranjay Mohan]

On an NVMe namespace that does not support metadata, it is possible to
send an IO command with metadata through io-passthru. This allows issues
like [1] to trigger in the completion code path.
nvme_map_user_request() doesn't check if the namespace supports metadata
before sending it forward. It also allows admin commands with metadata to
be processed as it ignores metadata when bdev == NULL and may report
success.

Reject an IO command with metadata when the NVMe namespace doesn't
support it and reject an admin command if it has metadata.

[1] https://lore.kernel.org/all/mb61pcylvnym8.fsf@amazon.com/

Suggested-by: Christoph Hellwig <hch at lst.de>
Signed-off-by: Puranjay Mohan <pjy at amazon.com>
Reviewed-by: Christoph Hellwig <hch at lst.de>
Reviewed-by: Sagi Grimberg <sagi at grimberg.me>
Reviewed-by: Anuj Gupta <anuj20.g at samsung.com>
---
V2: https://lore.kernel.org/all/20240827132327.1704-1-pjy@amazon.com/
Changes in V3
- Reject admin commands with metadata by also failing if there's no bdev

V1: https://lore.kernel.org/all/20240827121701.48792-1-pjy@amazon.com/
Changes in V2:
- Add a flag called 'has_metadata' and use it for the support check and
also for the check before calling bio_integrity_map_user()
---
 drivers/nvme/host/ioctl.c | 22 ++++++++++++++--------
 1 file changed, 14 insertions(+), 8 deletions(-)

diff --git a/drivers/nvme/host/ioctl.c b/drivers/nvme/host/ioctl.c
index f1d58e70933f..15c93ce07e26 100644
--- a/drivers/nvme/host/ioctl.c
+++ b/drivers/nvme/host/ioctl.c
@@ -4,6 +4,7 @@
  * Copyright (c) 2017-2021 Christoph Hellwig.
  */
 #include <linux/bio-integrity.h>
+#include <linux/blk-integrity.h>
 #include <linux/ptrace.h>	/* for force_successful_syscall_return */
 #include <linux/nvme_ioctl.h>
 #include <linux/io_uring/cmd.h>
@@ -119,9 +120,14 @@ static int nvme_map_user_request(struct request *req, u64 ubuffer,
 	struct request_queue *q = req->q;
 	struct nvme_ns *ns = q->queuedata;
 	struct block_device *bdev = ns ? ns->disk->part0 : NULL;
+	bool supports_metadata = bdev && blk_get_integrity(bdev->bd_disk);
+	bool has_metadata = meta_buffer && meta_len;
 	struct bio *bio = NULL;
 	int ret;
 
+	if (has_metadata && !supports_metadata)
+		return -EINVAL;
+
 	if (ioucmd && (ioucmd->flags & IORING_URING_CMD_FIXED)) {
 		struct iov_iter iter;
 
@@ -143,15 +149,15 @@ static int nvme_map_user_request(struct request *req, u64 ubuffer,
 		goto out;
 
 	bio = req->bio;
-	if (bdev) {
+	if (bdev)
 		bio_set_dev(bio, bdev);
-		if (meta_buffer && meta_len) {
-			ret = bio_integrity_map_user(bio, meta_buffer, meta_len,
-						     meta_seed);
-			if (ret)
-				goto out_unmap;
-			req->cmd_flags |= REQ_INTEGRITY;
-		}
+
+	if (has_metadata) {
+		ret = bio_integrity_map_user(bio, meta_buffer, meta_len,
+					     meta_seed);
+		if (ret)
+			goto out_unmap;
+		req->cmd_flags |= REQ_INTEGRITY;
 	}
 
 	return ret;
-- 
2.40.1