nvme: use kref_get_unless_zero in nvme_find_get_ns

[ Upstream commit 2dd4122854f697afc777582d18548dded03ce5dd ]

For kref_get_unless_zero to protect against lookup vs free races we need
to use it in all places where we aren't guaranteed to already hold a
reference.  There is no such guarantee in nvme_find_get_ns, so switch to
kref_get_unless_zero in this function.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index 37f9039..0655f45 100644 (file)
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -2299,7 +2299,8 @@ static struct nvme_ns *nvme_find_get_ns(struct nvme_ctrl *ctrl, unsigned nsid)
        mutex_lock(&ctrl->namespaces_mutex);
        list_for_each_entry(ns, &ctrl->namespaces, list) {
                if (ns->ns_id == nsid) {
-                       kref_get(&ns->kref);
+                       if (!kref_get_unless_zero(&ns->kref))
+                               continue;
                        ret = ns;
                        break;
                }