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From: Breno Leitao <leitao@debian.org>
To: "David S. Miller" <davem@davemloft.net>,
	Eric Dumazet <edumazet@google.com>,
	Jakub Kicinski <kuba@kernel.org>,
	Paolo Abeni <pabeni@redhat.com>
Cc: thepacketgeek@gmail.com,
	Aijay Adams <aijay@meta.com>,
	netdev@vger.kernel.org (open list:NETWORKING DRIVERS),
	linux-kernel@vger.kernel.org (open list)
Subject: [PATCH net-next] netconsole: Do not shutdown dynamic configuration if cmdline is invalid
Date: Fri, 10 May 2024 03:30:05 -0700
Message-ID: <20240510103005.3001545-1-leitao@debian.org>
Precedence: bulk
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit

If a user provides an invalid netconsole configuration during boot time
(e.g., specifying an invalid ethX interface), netconsole will be
entirely disabled. Consequently, the user won't be able to create new
entries in /sys/kernel/config/netconsole/ as that directory does not
exist.

Apart from misconfiguration, another issue arises when ethX is loaded as
a module and the netconsole= line in the command line points to ethX,
resulting in an obvious failure. This renders netconsole unusable, as
/sys/kernel/config/netconsole/ will never appear. This is more annoying
since users reconfigure (or just toggle) the configuratin later (see
commit 5fbd6cdbe304b ("netconsole: Attach cmdline target to dynamic
target"))

Create /sys/kernel/config/netconsole/ even if the command line arguments
are invalid, so, users can create dynamic entries in netconsole.

Reported-by: Aijay Adams <aijay@meta.com>
Signed-off-by: Breno Leitao <leitao@debian.org>
---
 drivers/net/netconsole.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/net/netconsole.c b/drivers/net/netconsole.c
index d7070dd4fe73..e69bc88c22a0 100644
--- a/drivers/net/netconsole.c
+++ b/drivers/net/netconsole.c
@@ -122,6 +122,11 @@ struct netconsole_target {
 	struct netpoll		np;
 };
 
+static inline bool dynamic_netconsole_enabled(void)
+{
+	return IS_ENABLED(CONFIG_NETCONSOLE_DYNAMIC);
+}
+
 #ifdef	CONFIG_NETCONSOLE_DYNAMIC
 
 static struct configfs_subsystem netconsole_subsys;
@@ -1262,6 +1267,8 @@ static int __init init_netconsole(void)
 		while ((target_config = strsep(&input, ";"))) {
 			nt = alloc_param_target(target_config, count);
 			if (IS_ERR(nt)) {
+				if (dynamic_netconsole_enabled())
+					continue;
 				err = PTR_ERR(nt);
 				goto fail;
 			}
-- 
2.43.0