nvme: fix handling of metadata_len for NVME_IOCTL_IO_CMD

The old code in nvme_user_cmd() passed the userspace virtual address
from nvme_passthru_cmd.metadata as the length of the metadata buffer
as well as the address to nvme_submit_user_cmd().

Fixes: 63263d60 ("nvme: Use metadata for passthrough commands")
Signed-off-by: Roland Dreier <roland@purestorage.com>
Reviewed-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>

drivers/nvme/host/core.c

@@ -1233,7 +1233,7 @@ static int nvme_user_cmd(struct nvme_ctrl *ctrl, struct nvme_ns *ns,
 	effects = nvme_passthru_start(ctrl, ns, cmd.opcode);
 	status = nvme_submit_user_cmd(ns ? ns->queue : ctrl->admin_q, &c,
 			(void __user *)(uintptr_t)cmd.addr, cmd.data_len,
-			(void __user *)(uintptr_t)cmd.metadata, cmd.metadata,
+			(void __user *)(uintptr_t)cmd.metadata, cmd.metadata_len,
 			0, &cmd.result, timeout);
 	nvme_passthru_end(ctrl, effects);