linux-kernel - [PATCH net-next 4/6] devlink: Require devlink lock during device reload

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Date:   Sun,  5 Dec 2021 10:22:04 +0200
From:   Leon Romanovsky <leon@...nel.org>
To:     "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     Leon Romanovsky <leonro@...dia.com>,
        Ido Schimmel <idosch@...dia.com>, Jiri Pirko <jiri@...dia.com>,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Subject: [PATCH net-next 4/6] devlink: Require devlink lock during device reload

From: Leon Romanovsky <leonro@...dia.com>

Devlink reload was implemented as a special command which does _SET_
operation, but doesn't take devlink->lock, while recursive devlink
calls that were part of .reload_up()/.reload_down() sequence took it.

This fragile flow was possible due to holding a big devlink lock
(devlink_mutex), which effectively stopped all devlink activities,
even unrelated to reloaded devlink.

So let's make sure that devlink reload behaves as other commands.

Tested-by: Ido Schimmel <idosch@...dia.com>
Signed-off-by: Leon Romanovsky <leonro@...dia.com>
---
 net/core/devlink.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/net/core/devlink.c b/net/core/devlink.c
index 7dd6091b97af..cbffafc1776f 100644
--- a/net/core/devlink.c
+++ b/net/core/devlink.c
@@ -8810,7 +8810,6 @@ static const struct genl_small_ops devlink_nl_ops[] = {
 		.validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
 		.doit = devlink_nl_cmd_reload,
 		.flags = GENL_ADMIN_PERM,
-		.internal_flags = DEVLINK_NL_FLAG_NO_LOCK,
 	},
 	{
 		.cmd = DEVLINK_CMD_PARAM_GET,
@@ -11448,10 +11447,15 @@ static void __net_exit devlink_pernet_pre_exit(struct net *net)
 			goto retry;
 
 		WARN_ON(!(devlink->features & DEVLINK_F_RELOAD));
+
+		mutex_lock(&devlink->lock);
+		xa_set_mark(&devlinks, devlink->index, DEVLINK_NESTED_LOCK);
 		err = devlink_reload(devlink, &init_net,
 				     DEVLINK_RELOAD_ACTION_DRIVER_REINIT,
 				     DEVLINK_RELOAD_LIMIT_UNSPEC,
 				     &actions_performed, NULL);
+		xa_clear_mark(&devlinks, devlink->index, DEVLINK_NESTED_LOCK);
+		mutex_unlock(&devlink->lock);
 		if (err && err != -EOPNOTSUPP)
 			pr_warn("Failed to reload devlink instance into init_net\n");
 retry:
-- 
2.33.1