Patch "nvme: use kref_get_unless_zero in nvme_find_get_ns" has been added to the 4.9-stable tree

Patch "nvme: use kref_get_unless_zero in nvme_find_get_ns" has been added to the 4.9-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    nvme: use kref_get_unless_zero in nvme_find_get_ns

to the 4.9-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     nvme-use-kref_get_unless_zero-in-nvme_find_get_ns.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From foo@baz Mon Dec 18 14:12:35 CET 2017
From: Christoph Hellwig <hch@lst.de>
Date: Wed, 18 Oct 2017 13:20:01 +0200
Subject: nvme: use kref_get_unless_zero in nvme_find_get_ns

From: Christoph Hellwig <hch@lst.de>


[ 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>
---
 drivers/nvme/host/core.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -1619,7 +1619,8 @@ static struct nvme_ns *nvme_find_get_ns(
 	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;
 		}


Patches currently in stable-queue which might be from hch@lst.de are

queue-4.9/xfs-fix-incorrect-extent-state-in-xfs_bmap_add_extent_unwritten_real.patch
queue-4.9/nvmet-confirm-sq-percpu-has-scheduled-and-switched-to-atomic.patch
queue-4.9/nvme-use-kref_get_unless_zero-in-nvme_find_get_ns.patch
queue-4.9/target-iscsi-fix-a-race-condition-in-iscsit_add_reject_from_cmd.patch
queue-4.9/nvme-loop-fix-a-possible-use-after-free-when-destroying-the-admin-queue.patch
queue-4.9/nvmet-rdma-fix-a-possible-uninitialized-variable-dereference.patch