[PATCH] Fix netns UAF introduced by commit 1be52169c348

[shaopeijie at cestc.cn]

From: Peijie Shao <shaopeijie at cestc.cn>

The patch is for nvme-tcp host side.

commit 1be52169c348
("nvme-tcp: fix selinux denied when calling sock_sendmsg")
uses sock_create_kern instead of sock_create to solve SELinux
problem, however sock_create_kern does not take a reference of
given netns, which results in a use-after-freewhen the
non-init_net netns is destroyed before sock_release.

For example: a container not share with host's network namespace
doing a 'nvme connect', and is stopped without 'nvme disconnect'.

The patch changes parameter current->nsproxy->net_ns to init_net,
makes the socket always belongs to the host. It also naturally
avoids changing sock's netns from previous creator's netns to
init_net when sock is re-created by nvme recovery path
(workqueue is in init_net namespace).

Signed-off-by: Peijie Shao <shaopeijie at cestc.cn>
---

Hi all,
This is the v1 patch. Before this version, I tried to
get_net(current->nsproxy->net_ns) in nvme_tcp_alloc_queue() to
fix the issue, but failed to find a suitable placeto do
put_net(). Because the socket is released by fput() internally.
I think code like below:
    nvme_tcp_free_queue() {
        fput()
        put_net()
    }
can not ensure the socket was released before put_net, since
someone is still holding the file.

So I prefer using the 'init_net' net namespace.

---
 drivers/nvme/host/tcp.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/nvme/host/tcp.c b/drivers/nvme/host/tcp.c
index 26c459f0198d..1b2d3d37656d 100644
--- a/drivers/nvme/host/tcp.c
+++ b/drivers/nvme/host/tcp.c
@@ -1789,7 +1789,13 @@ static int nvme_tcp_alloc_queue(struct nvme_ctrl *nctrl, int qid,
 		queue->cmnd_capsule_len = sizeof(struct nvme_command) +
 						NVME_TCP_ADMIN_CCSZ;
 
-	ret = sock_create_kern(current->nsproxy->net_ns,
+	/* sock_create_kern() does not take a reference to
+	 * current->nsproxy->net_ns, use init_net instead.
+	 * This also avoid changing sock's netns from previous
+	 * creator's netns to init_net when sock is re-created
+	 * by nvme recovery path.
+	 */
+	ret = sock_create_kern(&init_net,
 			ctrl->addr.ss_family, SOCK_STREAM,
 			IPPROTO_TCP, &queue->sock);
 	if (ret) {
-- 
2.43.0