mptcp: only allow set existing scheduler for net.mptcp.scheduler

commit 6963c508fd7ab66ae0b7ae3db9a62ca6267f1ae8 upstream.

The current behavior is to accept any strings as inputs, this results in
an inconsistent result where an unexisting scheduler can be set:

  # sysctl -w net.mptcp.scheduler=notdefault
  net.mptcp.scheduler = notdefault

This patch changes this behavior by checking for existing scheduler
before accepting the input.

Fixes: e3b2870b6d22 ("mptcp: add a new sysctl scheduler")
Cc: stable@vger.kernel.org
Signed-off-by: Gregory Detal <gregory.detal@gmail.com>
Reviewed-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Tested-by: Geliang Tang <geliang@kernel.org>
Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Link: https://lore.kernel.org/r/20240506-upstream-net-20240506-mptcp-sched-exist-v1-1-2ed1529e521e@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 38 insertions, 1 deletions

diff --git a/net/mptcp/ctrl.c b/net/mptcp/ctrl.c
index e72b518c5d02..de75df904a00 100644
--- a/net/mptcp/ctrl.c
+++ b/net/mptcp/ctrl.c
@@ -87,6 +87,43 @@ static void mptcp_pernet_set_defaults(struct mptcp_pernet *pernet)
 }
 
 #ifdef CONFIG_SYSCTL
+static int mptcp_set_scheduler(const struct net *net, const char *name)
+{
+	struct mptcp_pernet *pernet = mptcp_get_pernet(net);
+	struct mptcp_sched_ops *sched;
+	int ret = 0;
+
+	rcu_read_lock();
+	sched = mptcp_sched_find(name);
+	if (sched)
+		strscpy(pernet->scheduler, name, MPTCP_SCHED_NAME_MAX);
+	else
+		ret = -ENOENT;
+	rcu_read_unlock();
+
+	return ret;
+}
+
+static int proc_scheduler(struct ctl_table *ctl, int write,
+			  void *buffer, size_t *lenp, loff_t *ppos)
+{
+	const struct net *net = current->nsproxy->net_ns;
+	char val[MPTCP_SCHED_NAME_MAX];
+	struct ctl_table tbl = {
+		.data = val,
+		.maxlen = MPTCP_SCHED_NAME_MAX,
+	};
+	int ret;
+
+	strscpy(val, mptcp_get_scheduler(net), MPTCP_SCHED_NAME_MAX);
+
+	ret = proc_dostring(&tbl, write, buffer, lenp, ppos);
+	if (write && ret == 0)
+		ret = mptcp_set_scheduler(net, val);
+
+	return ret;
+}
+
 static struct ctl_table mptcp_sysctl_table[] = {
 	{
 		.procname = "enabled",
@@ -139,7 +176,7 @@ static struct ctl_table mptcp_sysctl_table[] = {
 		.procname = "scheduler",
 		.maxlen	= MPTCP_SCHED_NAME_MAX,
 		.mode = 0644,
-		.proc_handler = proc_dostring,
+		.proc_handler = proc_scheduler,
 	},
 	{}
 };