From cf7ad3030271c55a7119a8c2162563e3f6e93879 Mon Sep 17 00:00:00 2001
From: Parav Pandit <parav@mellanox.com>
Date: Fri, 21 Dec 2018 16:19:24 +0200
Subject: [PATCH 1/1] IB/umad: Avoid destroying device while it is accessed
Git-commit: cf7ad3030271c55a7119a8c2162563e3f6e93879
Patch-mainline: v5.0
References: bsc#1111666

ib_umad_reg_agent2() and ib_umad_reg_agent() access the device name in
dev_notice(), while concurrently, ib_umad_kill_port() can destroy the
device using device_destroy().

        cpu-0                               cpu-1
        -----                               -----
    ib_umad_ioctl()
        [...]                            ib_umad_kill_port()
                                              device_destroy(dev)

        ib_umad_reg_agent()
            dev_notice(dev)

Therefore, first mark ib_dev as NULL, to block any further access in file
ops, unregister the mad agent and destroy the device at the end after
mutex is unlocked.

This ensures that device doesn't get destroyed, while it may get accessed.

Fixes: 0f29b46d49b0 ("IB/mad: add new ioctl to ABI to support new registration options")
Signed-off-by: Parav Pandit <parav@mellanox.com>
Reviewed-by: Jack Morgenstein <jackm@mellanox.com>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
Acked-by: Nicolas Morey-Chaisemartin <nmoreychaisemartin@suse.com>
---
 drivers/infiniband/core/user_mad.c | 22 +++++++++++++---------
 1 file changed, 13 insertions(+), 9 deletions(-)

diff --git a/drivers/infiniband/core/user_mad.c b/drivers/infiniband/core/user_mad.c
index 52ebb1711d14..0204a4fefd13 100644
--- a/drivers/infiniband/core/user_mad.c
+++ b/drivers/infiniband/core/user_mad.c
@@ -1244,17 +1244,11 @@ static void ib_umad_kill_port(struct ib_umad_port *port)
 	struct ib_umad_file *file;
 	int id;
 
-	dev_set_drvdata(port->dev,    NULL);
-	dev_set_drvdata(port->sm_dev, NULL);
-
-	device_destroy(&umad_class, port->cdev.dev);
-	device_destroy(&umad_class, port->sm_cdev.dev);
-
-	cdev_del(&port->cdev);
-	cdev_del(&port->sm_cdev);
-
 	mutex_lock(&port->file_mutex);
 
+	/* Mark ib_dev NULL and block ioctl or other file ops to progress
+	 * further.
+	 */
 	port->ib_dev = NULL;
 
 	list_for_each_entry(file, &port->file_list, port_list) {
@@ -1268,6 +1262,16 @@ static void ib_umad_kill_port(struct ib_umad_port *port)
 	}
 
 	mutex_unlock(&port->file_mutex);
+
+	dev_set_drvdata(port->dev,    NULL);
+	dev_set_drvdata(port->sm_dev, NULL);
+
+	device_destroy(&umad_class, port->cdev.dev);
+	device_destroy(&umad_class, port->sm_cdev.dev);
+
+	cdev_del(&port->cdev);
+	cdev_del(&port->sm_cdev);
+
 	ida_free(&umad_ida, port->dev_num);
 }
 
-- 
2.26.2