[PATCH] nvme-tcp: fix a possible UAF when failing to allocate an io queue

[Sagi Grimberg]

When we allocate a nvme-tcp queue, we set the data_ready callback before
we actually need to use it. This creates the potential that if a stray
controller sends us data on the socket before we connect, we can trigger
the io_work and start consuming the socket.

In this case reported: we failed to allocate one of the io queues, and
as we start releasing the queues that we already allocated, we get
a UAF [1] from the io_work which is running before it should really.

Fix this by setting the socket ops callbacks only before we start the
queue, so that we can't accidently schedule the io_work in the initialization
phase before the queue started.

[1]:
[16802.107284] nvme nvme4: starting error recovery
[16802.109166] nvme nvme4: Reconnecting in 10 seconds...
[16812.173535] nvme nvme4: failed to connect socket: -111
[16812.173745] nvme nvme4: Failed reconnect attempt 1
[16812.173747] nvme nvme4: Reconnecting in 10 seconds...
[16822.413555] nvme nvme4: failed to connect socket: -111
[16822.413762] nvme nvme4: Failed reconnect attempt 2
[16822.413765] nvme nvme4: Reconnecting in 10 seconds...
[16832.661274] nvme nvme4: creating 32 I/O queues.
[16833.919887] BUG: kernel NULL pointer dereference, address: 0000000000000088
[16833.920068] nvme nvme4: Failed reconnect attempt 3
[16833.920094] #PF: supervisor write access in kernel mode
[16833.920261] nvme nvme4: Reconnecting in 10 seconds...
[16833.920368] #PF: error_code(0x0002) - not-present page
[16833.921086] Workqueue: nvme_tcp_wq nvme_tcp_io_work [nvme_tcp]
[16833.921191] RIP: 0010:_raw_spin_lock_bh+0x17/0x30
...
[16833.923138] Call Trace:
[16833.923271]  <TASK>
[16833.923402]  lock_sock_nested+0x1e/0x50
[16833.923545]  nvme_tcp_try_recv+0x40/0xa0 [nvme_tcp]
[16833.923685]  nvme_tcp_io_work+0x68/0xa0 [nvme_tcp]
[16833.923824]  process_one_work+0x1e8/0x390
[16833.923969]  worker_thread+0x53/0x3d0
[16833.924104]  ? process_one_work+0x390/0x390
[16833.924240]  kthread+0x124/0x150
[16833.924376]  ? set_kthread_struct+0x50/0x50
[16833.924518]  ret_from_fork+0x1f/0x30
[16833.924655]  </TASK>

Reported-by: Yanjun Zhang <zhangyanjun at cestc.cn>
Signed-off-by: Sagi Grimberg <sagi at grimberg.me>
---
Yanjun, I'll be waiting for your Tested-by tag. Need to
in order to apply this fix.

 drivers/nvme/host/tcp.c | 30 +++++++++++++++---------------
 1 file changed, 15 insertions(+), 15 deletions(-)

diff --git a/drivers/nvme/host/tcp.c b/drivers/nvme/host/tcp.c
index 42c0598c31f2..a8f3d8052b8d 100644
--- a/drivers/nvme/host/tcp.c
+++ b/drivers/nvme/host/tcp.c
@@ -1620,22 +1620,7 @@ static int nvme_tcp_alloc_queue(struct nvme_ctrl *nctrl, int qid)
 	if (ret)
 		goto err_init_connect;
 
-	queue->rd_enabled = true;
 	set_bit(NVME_TCP_Q_ALLOCATED, &queue->flags);
-	nvme_tcp_init_recv_ctx(queue);
-
-	write_lock_bh(&queue->sock->sk->sk_callback_lock);
-	queue->sock->sk->sk_user_data = queue;
-	queue->state_change = queue->sock->sk->sk_state_change;
-	queue->data_ready = queue->sock->sk->sk_data_ready;
-	queue->write_space = queue->sock->sk->sk_write_space;
-	queue->sock->sk->sk_data_ready = nvme_tcp_data_ready;
-	queue->sock->sk->sk_state_change = nvme_tcp_state_change;
-	queue->sock->sk->sk_write_space = nvme_tcp_write_space;
-#ifdef CONFIG_NET_RX_BUSY_POLL
-	queue->sock->sk->sk_ll_usec = 1;
-#endif
-	write_unlock_bh(&queue->sock->sk->sk_callback_lock);
 
 	return 0;
 
@@ -1693,6 +1678,21 @@ static int nvme_tcp_start_queue(struct nvme_ctrl *nctrl, int idx)
 	struct nvme_tcp_ctrl *ctrl = to_tcp_ctrl(nctrl);
 	int ret;
 
+	queue->rd_enabled = true;
+	nvme_tcp_init_recv_ctx(queue);
+	write_lock_bh(&queue->sock->sk->sk_callback_lock);
+	queue->sock->sk->sk_user_data = queue;
+	queue->state_change = queue->sock->sk->sk_state_change;
+	queue->data_ready = queue->sock->sk->sk_data_ready;
+	queue->write_space = queue->sock->sk->sk_write_space;
+	queue->sock->sk->sk_data_ready = nvme_tcp_data_ready;
+	queue->sock->sk->sk_state_change = nvme_tcp_state_change;
+	queue->sock->sk->sk_write_space = nvme_tcp_write_space;
+#ifdef CONFIG_NET_RX_BUSY_POLL
+	queue->sock->sk->sk_ll_usec = 1;
+#endif
+	write_unlock_bh(&queue->sock->sk->sk_callback_lock);
+
 	if (idx)
 		ret = nvmf_connect_io_queue(nctrl, idx);
 	else
-- 
2.34.1