linux-kernel - [PATCH v3 1/4] nvmet: Fix use-after-free bug when a port is removed

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Date:   Wed, 31 Jul 2019 17:35:31 -0600
From:   Logan Gunthorpe <logang@...tatee.com>
To:     linux-kernel@...r.kernel.org, linux-nvme@...ts.infradead.org
Cc:     Christoph Hellwig <hch@....de>, Keith Busch <kbusch@...nel.org>,
        Jens Axboe <axboe@...com>, Sagi Grimberg <sagi@...mberg.me>,
        Chaitanya Kulkarni <chaitanya.kulkarni@....com>,
        Max Gurtovoy <maxg@...lanox.com>,
        Logan Gunthorpe <logang@...tatee.com>
Subject: [PATCH v3 1/4] nvmet: Fix use-after-free bug when a port is removed

When a port is removed through configfs, any connected controllers
are still active and can still send commands. This causes a
use-after-free bug which is detected by KASAN for any admin command
that dereferences req->port (like in nvmet_execute_identify_ctrl).

To fix this, disconnect all active controllers when a subsystem is
removed from a port. This ensures there are no active controllers
when the port is eventually removed.

Signed-off-by: Logan Gunthorpe <logang@...tatee.com>
Reviewed-by: Sagi Grimberg <sagi@...mberg.me>
Reviewed-by: Max Gurtovoy <maxg@...lanox.com>
---
 drivers/nvme/target/configfs.c |  1 +
 drivers/nvme/target/core.c     | 12 ++++++++++++
 drivers/nvme/target/nvmet.h    |  3 +++
 3 files changed, 16 insertions(+)

diff --git a/drivers/nvme/target/configfs.c b/drivers/nvme/target/configfs.c
index cd52b9f15376..98613a45bd3b 100644
--- a/drivers/nvme/target/configfs.c
+++ b/drivers/nvme/target/configfs.c
@@ -675,6 +675,7 @@ static void nvmet_port_subsys_drop_link(struct config_item *parent,
 
 found:
 	list_del(&p->entry);
+	nvmet_port_del_ctrls(port, subsys);
 	nvmet_port_disc_changed(port, subsys);
 
 	if (list_empty(&port->subsystems))
diff --git a/drivers/nvme/target/core.c b/drivers/nvme/target/core.c
index dad0243c7c96..b86a23aa9020 100644
--- a/drivers/nvme/target/core.c
+++ b/drivers/nvme/target/core.c
@@ -280,6 +280,18 @@ void nvmet_unregister_transport(const struct nvmet_fabrics_ops *ops)
 }
 EXPORT_SYMBOL_GPL(nvmet_unregister_transport);
 
+void nvmet_port_del_ctrls(struct nvmet_port *port, struct nvmet_subsys *subsys)
+{
+	struct nvmet_ctrl *ctrl;
+
+	mutex_lock(&subsys->lock);
+	list_for_each_entry(ctrl, &subsys->ctrls, subsys_entry) {
+		if (ctrl->port == port)
+			ctrl->ops->delete_ctrl(ctrl);
+	}
+	mutex_unlock(&subsys->lock);
+}
+
 int nvmet_enable_port(struct nvmet_port *port)
 {
 	const struct nvmet_fabrics_ops *ops;
diff --git a/drivers/nvme/target/nvmet.h b/drivers/nvme/target/nvmet.h
index 6ee66c610739..c51f8dd01dc4 100644
--- a/drivers/nvme/target/nvmet.h
+++ b/drivers/nvme/target/nvmet.h
@@ -418,6 +418,9 @@ void nvmet_port_send_ana_event(struct nvmet_port *port);
 int nvmet_register_transport(const struct nvmet_fabrics_ops *ops);
 void nvmet_unregister_transport(const struct nvmet_fabrics_ops *ops);
 
+void nvmet_port_del_ctrls(struct nvmet_port *port,
+			  struct nvmet_subsys *subsys);
+
 int nvmet_enable_port(struct nvmet_port *port);
 void nvmet_disable_port(struct nvmet_port *port);
 
-- 
2.20.1