From: Jakub Kicinski <kuba@kernel.org>
Date: Sat, 30 Oct 2021 16:15:01 -0700
Subject: netdevsim: take rtnl_lock when assigning num_vfs
Patch-mainline: v5.16-rc1
Git-commit: 26c37d89f61d84dda55feefeafb4907f2a7cd944
References: jsc#PED-1549

Legacy VF NDOs look at num_vfs and then based on that
index into vfconfig. If we don't rtnl_lock() num_vfs
may get set to 0 and vfconfig freed/replaced while
the NDO is running.

We don't need to protect replacing vfconfig since it's
only done when num_vfs is 0.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 drivers/net/netdevsim/bus.c |   14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

--- a/drivers/net/netdevsim/bus.c
+++ b/drivers/net/netdevsim/bus.c
@@ -24,6 +24,14 @@ static struct nsim_bus_dev *to_nsim_bus_
 	return container_of(dev, struct nsim_bus_dev, dev);
 }
 
+static void
+nsim_bus_dev_set_vfs(struct nsim_bus_dev *nsim_bus_dev, unsigned int num_vfs)
+{
+	rtnl_lock();
+	nsim_bus_dev->num_vfs = num_vfs;
+	rtnl_unlock();
+}
+
 static int nsim_bus_dev_vfs_enable(struct nsim_bus_dev *nsim_bus_dev,
 				   unsigned int num_vfs)
 {
@@ -35,13 +43,13 @@ static int nsim_bus_dev_vfs_enable(struc
 
 	if (!nsim_bus_dev->vfconfigs)
 		return -ENOMEM;
-	nsim_bus_dev->num_vfs = num_vfs;
+	nsim_bus_dev_set_vfs(nsim_bus_dev, num_vfs);
 
 	nsim_dev = dev_get_drvdata(&nsim_bus_dev->dev);
 	if (nsim_esw_mode_is_switchdev(nsim_dev)) {
 		err = nsim_esw_switchdev_enable(nsim_dev, NULL);
 		if (err)
-			nsim_bus_dev->num_vfs = 0;
+			nsim_bus_dev_set_vfs(nsim_bus_dev, 0);
 	}
 
 	return err;
@@ -51,7 +59,7 @@ void nsim_bus_dev_vfs_disable(struct nsi
 {
 	struct nsim_dev *nsim_dev;
 
-	nsim_bus_dev->num_vfs = 0;
+	nsim_bus_dev_set_vfs(nsim_bus_dev, 0);
 	nsim_dev = dev_get_drvdata(&nsim_bus_dev->dev);
 	if (nsim_esw_mode_is_switchdev(nsim_dev))
 		nsim_esw_legacy_enable(nsim_dev, NULL);