linux-kernel - [PATCH] net: core: dev.c confirmed to use classic sockaddr

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Message-Id: <20241217012445.work.979-kees@kernel.org>
Date: Mon, 16 Dec 2024 17:24:49 -0800
From: Kees Cook <kees@...nel.org>
To: "David S. Miller" <davem@...emloft.net>
Cc: Kees Cook <kees@...nel.org>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>,
	netdev@...r.kernel.org,
	Simon Horman <horms@...nel.org>,
	David Ahern <dsahern@...nel.org>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	Lorenzo Bianconi <lorenzo@...nel.org>,
	Joe Damato <jdamato@...tly.com>,
	Alexander Lobakin <aleksander.lobakin@...el.com>,
	linux-kernel@...r.kernel.org,
	linux-hardening@...r.kernel.org
Subject: [PATCH] net: core: dev.c confirmed to use classic sockaddr

As part of trying to clean up struct sock_addr, add comments about the
sockaddr arguments of dev_[gs]et_mac_address() being actual classic "max
14 bytes in sa_data" sockaddr instances and not struct sockaddr_storage.

Signed-off-by: Kees Cook <kees@...nel.org>
---
Cc: "David S. Miller" <davem@...emloft.net>
Cc: Eric Dumazet <edumazet@...gle.com>
Cc: Jakub Kicinski <kuba@...nel.org>
Cc: Paolo Abeni <pabeni@...hat.com>
Cc: netdev@...r.kernel.org
---
 net/core/dev.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/net/core/dev.c b/net/core/dev.c
index 45a8c3dd4a64..5abfd29a35bf 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -9183,7 +9183,8 @@ EXPORT_SYMBOL(dev_pre_changeaddr_notify);
 /**
  *	dev_set_mac_address - Change Media Access Control Address
  *	@dev: device
- *	@sa: new address
+ *	@sa: new address in a classic "struct sockaddr", which will never
+ *	     have more than 14 bytes in @sa::sa_data
  *	@extack: netlink extended ack
  *
  *	Change the hardware (MAC) address of the device
@@ -9217,6 +9218,7 @@ EXPORT_SYMBOL(dev_set_mac_address);
 
 DECLARE_RWSEM(dev_addr_sem);
 
+/* "sa" is a classic sockaddr: it will only ever use 14 bytes from sa_data. */
 int dev_set_mac_address_user(struct net_device *dev, struct sockaddr *sa,
 			     struct netlink_ext_ack *extack)
 {
@@ -9229,6 +9231,7 @@ int dev_set_mac_address_user(struct net_device *dev, struct sockaddr *sa,
 }
 EXPORT_SYMBOL(dev_set_mac_address_user);
 
+/* "sa" is a classic sockaddr: it will only ever use 14 bytes from sa_data. */
 int dev_get_mac_address(struct sockaddr *sa, struct net *net, char *dev_name)
 {
 	size_t size = sizeof(sa->sa_data_min);
-- 
2.34.1