netdev - [PATCH net-next] net: netlink: reduce extack cookie size

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-ID: <20250516115927.38209-2-johannes@sipsolutions.net>
Date: Fri, 16 May 2025 13:59:27 +0200
From: Johannes Berg <johannes@...solutions.net>
To: linux-wireless@...r.kernel.org,
	netdev@...r.kernel.org
Cc: Johannes Berg <johannes.berg@...el.com>
Subject: [PATCH net-next] net: netlink: reduce extack cookie size

From: Johannes Berg <johannes.berg@...el.com>

Seems like the extack cookie hasn't found any users outside
of wireless, which always uses nl_set_extack_cookie_u64().
Thus, allocating 20 bytes for it is pointless, reduce that
to 8 bytes, and add a BUILD_BUG_ON() to ensure it's enough
(obviously it is, for a u64, but in case it changes again.)

Signed-off-by: Johannes Berg <johannes.berg@...el.com>
---
 include/linux/netlink.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/include/linux/netlink.h b/include/linux/netlink.h
index c3ae84a77e16..882e9c1b6c1d 100644
--- a/include/linux/netlink.h
+++ b/include/linux/netlink.h
@@ -63,7 +63,7 @@ netlink_kernel_create(struct net *net, int unit, struct netlink_kernel_cfg *cfg)
 }
 
 /* this can be increased when necessary - don't expose to userland */
-#define NETLINK_MAX_COOKIE_LEN	20
+#define NETLINK_MAX_COOKIE_LEN	8
 #define NETLINK_MAX_FMTMSG_LEN	80
 
 /**
@@ -212,6 +212,7 @@ static inline void nl_set_extack_cookie_u64(struct netlink_ext_ack *extack,
 {
 	if (!extack)
 		return;
+	BUILD_BUG_ON(sizeof(extack->cookie) < sizeof(cookie));
 	memcpy(extack->cookie, &cookie, sizeof(cookie));
 	extack->cookie_len = sizeof(cookie);
 }
-- 
2.49.0