netdev - [PATCH v4 3/4] net/sched: Load modules via their alias

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Message-ID: <20240123135242.11430-4-mkoutny@suse.com>
Date: Tue, 23 Jan 2024 14:52:41 +0100
From: Michal Koutný <mkoutny@...e.com>
To: netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	bpf@...r.kernel.org,
	cake@...ts.bufferbloat.net
Cc: "David S . Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>,
	Jamal Hadi Salim <jhs@...atatu.com>,
	Cong Wang <xiyou.wangcong@...il.com>,
	Jiri Pirko <jiri@...nulli.us>,
	Alexei Starovoitov <ast@...nel.org>,
	Daniel Borkmann <daniel@...earbox.net>,
	Andrii Nakryiko <andrii@...nel.org>,
	Martin KaFai Lau <martin.lau@...ux.dev>,
	Song Liu <song@...nel.org>,
	Yonghong Song <yonghong.song@...ux.dev>,
	John Fastabend <john.fastabend@...il.com>,
	KP Singh <kpsingh@...nel.org>,
	Stanislav Fomichev <sdf@...gle.com>,
	Hao Luo <haoluo@...gle.com>,
	Jiri Olsa <jolsa@...nel.org>,
	Toke Høiland-Jørgensen <toke@...e.dk>,
	Vinicius Costa Gomes <vinicius.gomes@...el.com>,
	Stephen Hemminger <stephen@...workplumber.org>,
	Petr Pavlu <ppavlu@...e.cz>,
	Michal Kubecek <mkubecek@...e.cz>,
	Martin Wilck <mwilck@...e.com>,
	Pedro Tammela <pctammela@...atatu.com>
Subject: [PATCH v4 3/4] net/sched: Load modules via their alias

The cls_,sch_,act_ modules may be loaded lazily during network
configuration but without user's awareness and control.

Switch the lazy loading from canonical module names to a module alias.
This allows finer control over lazy loading, the precedent from
commit 7f78e0351394 ("fs: Limit sys_mount to only request filesystem
modules.") explains it already:

	Using aliases means user space can control the policy of which
	filesystem^W net/sched modules are auto-loaded by editing
	/etc/modprobe.d/*.conf with blacklist and alias directives.
	Allowing simple, safe, well understood work-arounds to known
	problematic software.

By default, nothing changes. However, if a specific module is
blacklisted (its canonical name), it won't be modprobe'd when requested
under its alias (i.e. kernel auto-loading). It would appear as if the
given module was unknown.

The module can still be loaded under its canonical name, which is an
explicit (privileged) user action.

Signed-off-by: Michal Koutný <mkoutny@...e.com>
---
 net/sched/act_api.c | 2 +-
 net/sched/cls_api.c | 2 +-
 net/sched/sch_api.c | 4 ++--
 3 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/net/sched/act_api.c b/net/sched/act_api.c
index 3e30d7260493..60c0fadfac6d 100644
--- a/net/sched/act_api.c
+++ b/net/sched/act_api.c
@@ -1363,7 +1363,7 @@ struct tc_action_ops *tc_action_load_ops(struct nlattr *nla, u32 flags,
 
 		if (rtnl_held)
 			rtnl_unlock();
-		request_module("act_%s", act_name);
+		request_module(NET_ACT_ALIAS_PREFIX "%s", name);
 		if (rtnl_held)
 			rtnl_lock();
 
diff --git a/net/sched/cls_api.c b/net/sched/cls_api.c
index 92a12e3d0fe6..b31b832598e7 100644
--- a/net/sched/cls_api.c
+++ b/net/sched/cls_api.c
@@ -257,7 +257,7 @@ tcf_proto_lookup_ops(const char *kind, bool rtnl_held,
 #ifdef CONFIG_MODULES
 	if (rtnl_held)
 		rtnl_unlock();
-	request_module("cls_%s", kind);
+	request_module(NET_CLS_ALIAS_PREFIX "%s", name);
 	if (rtnl_held)
 		rtnl_lock();
 	ops = __tcf_proto_lookup_ops(kind);
diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c
index 36b025cc4fd2..9d928f6a473a 100644
--- a/net/sched/sch_api.c
+++ b/net/sched/sch_api.c
@@ -228,7 +228,7 @@ int qdisc_set_default(const char *name)
 	if (!ops) {
 		/* Not found, drop lock and try to load module */
 		write_unlock(&qdisc_mod_lock);
-		request_module("sch_%s", name);
+		request_module(NET_SCH_ALIAS_PREFIX "%s", name);
 		write_lock(&qdisc_mod_lock);
 
 		ops = qdisc_lookup_default(name);
@@ -1275,7 +1275,7 @@ static struct Qdisc *qdisc_create(struct net_device *dev,
 			 * go away in the mean time.
 			 */
 			rtnl_unlock();
-			request_module("sch_%s", name);
+			request_module(NET_SCH_ALIAS_PREFIX "%s", name);
 			rtnl_lock();
 			ops = qdisc_lookup_ops(kind);
 			if (ops != NULL) {
-- 
2.43.0