netdev - [RFC net-next 03/10] devlink: protect devlink->dev by the instance lock

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Message-Id: <20221217011953.152487-4-kuba@kernel.org>
Date:   Fri, 16 Dec 2022 17:19:46 -0800
From:   Jakub Kicinski <kuba@...nel.org>
To:     jiri@...nulli.us, jacob.e.keller@...el.com, leon@...nel.org
Cc:     netdev@...r.kernel.org, Jakub Kicinski <kuba@...nel.org>
Subject: [RFC net-next 03/10] devlink: protect devlink->dev by the instance lock

devlink->dev is assumed to be always valid as long as any
outstanding reference to the devlink instance exists.

In prep for weakening of the references take the instance lock.

Signed-off-by: Jakub Kicinski <kuba@...nel.org>
---
 net/devlink/basic.c         | 7 +++----
 net/devlink/devl_internal.h | 3 ++-
 net/devlink/netlink.c       | 9 ++++++---
 3 files changed, 11 insertions(+), 8 deletions(-)

diff --git a/net/devlink/basic.c b/net/devlink/basic.c
index ceac4343698b..5f33d74eef83 100644
--- a/net/devlink/basic.c
+++ b/net/devlink/basic.c
@@ -6314,12 +6314,10 @@ static int devlink_nl_cmd_region_read_dumpit(struct sk_buff *skb,
 
 	start_offset = dump->start_offset;
 
-	devlink = devlink_get_from_attrs(sock_net(cb->skb->sk), attrs);
+	devlink = devlink_get_from_attrs_lock(sock_net(cb->skb->sk), attrs);
 	if (IS_ERR(devlink))
 		return PTR_ERR(devlink);
 
-	devl_lock(devlink);
-
 	if (!attrs[DEVLINK_ATTR_REGION_NAME]) {
 		NL_SET_ERR_MSG(cb->extack, "No region name provided");
 		err = -EINVAL;
@@ -7735,9 +7733,10 @@ devlink_health_reporter_get_from_cb(struct netlink_callback *cb)
 	struct nlattr **attrs = info->attrs;
 	struct devlink *devlink;
 
-	devlink = devlink_get_from_attrs(sock_net(cb->skb->sk), attrs);
+	devlink = devlink_get_from_attrs_lock(sock_net(cb->skb->sk), attrs);
 	if (IS_ERR(devlink))
 		return NULL;
+	devl_unlock(devlink);
 
 	reporter = devlink_health_reporter_get_from_attrs(devlink, attrs);
 	devlink_put(devlink);
diff --git a/net/devlink/devl_internal.h b/net/devlink/devl_internal.h
index ef0369449592..c3977c69552a 100644
--- a/net/devlink/devl_internal.h
+++ b/net/devlink/devl_internal.h
@@ -129,7 +129,8 @@ struct devlink_gen_cmd {
 
 extern const struct genl_small_ops devlink_nl_ops[56];
 
-struct devlink *devlink_get_from_attrs(struct net *net, struct nlattr **attrs);
+struct devlink *
+devlink_get_from_attrs_lock(struct net *net, struct nlattr **attrs);
 
 void devlink_notify_unregister(struct devlink *devlink);
 void devlink_notify_register(struct devlink *devlink);
diff --git a/net/devlink/netlink.c b/net/devlink/netlink.c
index 7eb39ccb2ae7..b38df704be1c 100644
--- a/net/devlink/netlink.c
+++ b/net/devlink/netlink.c
@@ -82,7 +82,8 @@ static const struct nla_policy devlink_nl_policy[DEVLINK_ATTR_MAX + 1] = {
 	[DEVLINK_ATTR_REGION_DIRECT] = { .type = NLA_FLAG },
 };
 
-struct devlink *devlink_get_from_attrs(struct net *net, struct nlattr **attrs)
+struct devlink *
+devlink_get_from_attrs_lock(struct net *net, struct nlattr **attrs)
 {
 	struct devlink *devlink;
 	unsigned long index;
@@ -96,9 +97,11 @@ struct devlink *devlink_get_from_attrs(struct net *net, struct nlattr **attrs)
 	devname = nla_data(attrs[DEVLINK_ATTR_DEV_NAME]);
 
 	devlinks_xa_for_each_registered_get(net, index, devlink) {
+		devl_lock(devlink);
 		if (strcmp(devlink->dev->bus->name, busname) == 0 &&
 		    strcmp(dev_name(devlink->dev), devname) == 0)
 			return devlink;
+		devl_unlock(devlink);
 		devlink_put(devlink);
 	}
 
@@ -113,10 +116,10 @@ static int devlink_nl_pre_doit(const struct genl_split_ops *ops,
 	struct devlink *devlink;
 	int err;
 
-	devlink = devlink_get_from_attrs(genl_info_net(info), info->attrs);
+	devlink = devlink_get_from_attrs_lock(genl_info_net(info), info->attrs);
 	if (IS_ERR(devlink))
 		return PTR_ERR(devlink);
-	devl_lock(devlink);
+
 	info->user_ptr[0] = devlink;
 	if (ops->internal_flags & DEVLINK_NL_FLAG_NEED_PORT) {
 		devlink_port = devlink_port_get_from_info(devlink, info);
-- 
2.38.1