[PATCH] nvme-core: warn and abort if shared ns with empty list

[Irvin Cote]

In nvme_find_ns_head if we find a shared ns but it has an empty
list or its refcount is 0 we gloss over it and go to the next.
Ignoring when such a case happens means that when nvme_find_ns_head
returns NULL, we could create a new nshead with the same nsid. Hence
we could find ourselves with two shared nsheads having the same nsid.
Instead warn the user through dev_err and exit.

Signed-off-by: Irvin Cote <irvincoteg at gmail.com>
---
 drivers/nvme/host/core.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index c8a471482421..175f1516083f 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -3341,6 +3341,11 @@ static struct nvme_ns_head *nvme_find_ns_head(struct nvme_ctrl *ctrl,
 			continue;
 		if (!list_empty(&h->list) && nvme_tryget_ns_head(h))
 			return h;
+		else {
+			dev_err(ctrl->device,
+				"Found shared namespace with empty list or 0 refcount\n");
+			return ERR_PTR(-ENOENT);
+		}
 	}
 
 	return NULL;
@@ -3535,6 +3540,12 @@ static int nvme_init_ns_head(struct nvme_ns *ns, struct nvme_ns_info *info)
 
 	mutex_lock(&ctrl->subsys->lock);
 	head = nvme_find_ns_head(ctrl, info->nsid);
+
+	if (IS_ERR(head)) {
+		ret = PTR_ERR(head);
+		goto out_unlock;
+	}
+
 	if (!head) {
 		ret = nvme_subsys_check_duplicate_ids(ctrl->subsys, &info->ids);
 		if (ret) {
-- 
2.40.1