[PATCH 4.19 15/24] mlxsw: core: Fix devlink unregister flow

[Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>]

4.19-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Shalom Toledo <shalomt@xxxxxxxxxxxx>

[ Upstream commit a22712a962912faf257e857ab6857f56a93cfb34 ]

After a failed reload, the driver is still registered to devlink, its
devlink instance is still allocated and the 'reload_fail' flag is set.
Then, in the next reload try, the driver's allocated devlink instance will
be freed without unregistering from devlink and its components (e.g,
resources). This scenario can cause a use-after-free if the user tries to
execute command via devlink user-space tool.

Fix by not freeing the devlink instance during reload (failed or not).

Fixes: 24cc68ad6c46 ("mlxsw: core: Add support for reload")
Signed-off-by: Shalom Toledo <shalomt@xxxxxxxxxxxx>
Reviewed-by: Jiri Pirko <jiri@xxxxxxxxxxxx>
Signed-off-by: Ido Schimmel <idosch@xxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 drivers/net/ethernet/mellanox/mlxsw/core.c |   24 +++++++++++++++++-------
 1 file changed, 17 insertions(+), 7 deletions(-)

--- a/drivers/net/ethernet/mellanox/mlxsw/core.c
+++ b/drivers/net/ethernet/mellanox/mlxsw/core.c
@@ -943,8 +943,8 @@ static int mlxsw_devlink_core_bus_device
 					     mlxsw_core->bus,
 					     mlxsw_core->bus_priv, true,
 					     devlink);
-	if (err)
-		mlxsw_core->reload_fail = true;
+	mlxsw_core->reload_fail = !!err;
+
 	return err;
 }
 
@@ -1083,8 +1083,15 @@ void mlxsw_core_bus_device_unregister(st
 {
 	struct devlink *devlink = priv_to_devlink(mlxsw_core);
 
-	if (mlxsw_core->reload_fail)
-		goto reload_fail;
+	if (mlxsw_core->reload_fail) {
+		if (!reload)
+			/* Only the parts that were not de-initialized in the
+			 * failed reload attempt need to be de-initialized.
+			 */
+			goto reload_fail_deinit;
+		else
+			return;
+	}
 
 	if (mlxsw_core->driver->fini)
 		mlxsw_core->driver->fini(mlxsw_core);
@@ -1098,9 +1105,12 @@ void mlxsw_core_bus_device_unregister(st
 	if (!reload)
 		devlink_resources_unregister(devlink, NULL);
 	mlxsw_core->bus->fini(mlxsw_core->bus_priv);
-	if (reload)
-		return;
-reload_fail:
+
+	return;
+
+reload_fail_deinit:
+	devlink_unregister(devlink);
+	devlink_resources_unregister(devlink, NULL);
 	devlink_free(devlink);
 }
 EXPORT_SYMBOL(mlxsw_core_bus_device_unregister);