linux-kernel - [PATCH] usb: gadget: u_ether: fix regression in setting fixed MAC address

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Message-Id: <20220603153459.32722-1-posteuca@mutex.one>
Date:   Fri,  3 Jun 2022 18:34:59 +0300
From:   Marian Postevca <posteuca@...ex.one>
To:     Felipe Balbi <balbi@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Marian Postevca <posteuca@...ex.one>, stable@...r.kernel.org,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] usb: gadget: u_ether: fix regression in setting fixed MAC address

In systemd systems setting a fixed MAC address through
the "dev_addr" module argument fails systematically.
When checking the MAC address after the interface is created
it always has the same but different MAC address to the one
supplied as argument.

This is partially caused by systemd which by default will
set an internally generated permanent MAC address for interfaces
that are marked as having a randomly generated address.

Commit 890d5b40908bfd1a ("usb: gadget: u_ether: fix race in
setting MAC address in setup phase") didn't take into account
the fact that the interface must be marked as having a set
MAC address when it's set as module argument.

Fixed by marking the interface with NET_ADDR_SET when
the "dev_addr" module argument is supplied.

Fixes: 890d5b40908bfd1a ("usb: gadget: u_ether: fix race in setting MAC address in setup phase")
Cc: stable@...r.kernel.org
Signed-off-by: Marian Postevca <posteuca@...ex.one>
---
 drivers/usb/gadget/function/u_ether.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/gadget/function/u_ether.c b/drivers/usb/gadget/function/u_ether.c
index 6f5d45ef2e39a..f51694f29de92 100644
--- a/drivers/usb/gadget/function/u_ether.c
+++ b/drivers/usb/gadget/function/u_ether.c
@@ -775,9 +775,13 @@ struct eth_dev *gether_setup_name(struct usb_gadget *g,
 	dev->qmult = qmult;
 	snprintf(net->name, sizeof(net->name), "%s%%d", netname);
 
-	if (get_ether_addr(dev_addr, addr))
+	if (get_ether_addr(dev_addr, addr)) {
+		net->addr_assign_type = NET_ADDR_RANDOM;
 		dev_warn(&g->dev,
 			"using random %s ethernet address\n", "self");
+	} else {
+		net->addr_assign_type = NET_ADDR_SET;
+	}
 	eth_hw_addr_set(net, addr);
 	if (get_ether_addr(host_addr, dev->host_mac))
 		dev_warn(&g->dev,
@@ -844,6 +848,10 @@ struct net_device *gether_setup_name_default(const char *netname)
 
 	eth_random_addr(dev->dev_mac);
 	pr_warn("using random %s ethernet address\n", "self");
+
+	/* by default we always have a random MAC address */
+	net->addr_assign_type = NET_ADDR_RANDOM;
+
 	eth_random_addr(dev->host_mac);
 	pr_warn("using random %s ethernet address\n", "host");
 
@@ -871,7 +879,6 @@ int gether_register_netdev(struct net_device *net)
 	dev = netdev_priv(net);
 	g = dev->gadget;
 
-	net->addr_assign_type = NET_ADDR_RANDOM;
 	eth_hw_addr_set(net, dev->dev_mac);
 
 	status = register_netdev(net);
@@ -912,6 +919,7 @@ int gether_set_dev_addr(struct net_device *net, const char *dev_addr)
 	if (get_ether_addr(dev_addr, new_addr))
 		return -EINVAL;
 	memcpy(dev->dev_mac, new_addr, ETH_ALEN);
+	net->addr_assign_type = NET_ADDR_SET;
 	return 0;
 }
 EXPORT_SYMBOL_GPL(gether_set_dev_addr);
-- 
2.35.1