[PATCH 2/2] nvmet: fix a race condition between release_queue and io_work

Maurizio Lombardi
2021-10-21T08:42:31Z

If the initiator executes a reset controller operation while
performing I/O, the target kernel will crash because of a race condition
between release_queue and io_work;
nvmet_tcp_uninit_data_in_cmds() may be executed while io_work
is running, calling flush_work(io_work) was not sufficient to
prevent this because io_work could requeue itself.

* Fix this bug by preventing io_work from being enqueued when
sk_user_data is NULL (it means that the queue is going to be deleted)

* Ensure that all the memory allocated for the commands' iovec is freed

Signed-off-by: Maurizio Lombardi <mlombard@redhat.com>
---
drivers/nvme/target/tcp.c | 13 +++++++++----
1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/drivers/nvme/target/tcp.c b/drivers/nvme/target/tcp.c
index 2f03a94725ae..1eedbd83c95f 100644
--- a/drivers/nvme/target/tcp.c
+++ b/drivers/nvme/target/tcp.c
@@ -551,6 +551,7 @@ static void nvmet_tcp_queue_response(struct nvmet_req *req)
struct nvmet_tcp_cmd *cmd =
container_of(req, struct nvmet_tcp_cmd, req);
struct nvmet_tcp_queue *queue = cmd->queue;
+ struct socket *sock = queue->sock;
struct nvme_sgl_desc *sgl;
u32 len;

@@ -570,7 +571,10 @@ static void nvmet_tcp_queue_response(struct nvmet_req *req)
}

llist_add(&cmd->lentry, &queue->resp_list);
- queue_work_on(queue_cpu(queue), nvmet_tcp_wq, &cmd->queue->io_work);
+ read_lock_bh(&sock->sk->sk_callback_lock);
+ if (likely(sock->sk->sk_user_data))
+ queue_work_on(queue_cpu(queue), nvmet_tcp_wq, &cmd->queue->io_work);
+ read_unlock_bh(&sock->sk->sk_callback_lock);
}

static void nvmet_tcp_execute_request(struct nvmet_tcp_cmd *cmd)
@@ -1427,7 +1431,9 @@ static void nvmet_tcp_uninit_data_in_cmds(struct nvmet_tcp_queue *queue)

for (i = 0; i < queue->nr_cmds; i++, cmd++) {
if (nvmet_tcp_need_data_in(cmd))
- nvmet_tcp_finish_cmd(cmd);
+ nvmet_req_uninit(&cmd->req);
+ nvmet_tcp_unmap_pdu_iovec(cmd);
+ nvmet_tcp_free_iovec(cmd);
}

if (!queue->nr_cmds && nvmet_tcp_need_data_in(&queue->connect)) {
@@ -1447,11 +1453,10 @@ static void nvmet_tcp_release_queue_work(struct work_struct *w)
mutex_unlock(&nvmet_tcp_queue_mutex);

nvmet_tcp_restore_socket_callbacks(queue);
- flush_work(&queue->io_work);
+ cancel_work_sync(&queue->io_work);

nvmet_tcp_uninit_data_in_cmds(queue);
nvmet_sq_destroy(&queue->nvme_sq);
- cancel_work_sync(&queue->io_work);
sock_release(queue->sock);
nvmet_tcp_free_cmds(queue);
if (queue->hdr_digest || queue->data_digest)
--
2.27.0