From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: stable@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	patches@lists.linux.dev,
	Xiao Liang <shaw.leon@gmail.com>,
	Maoyi Xie <maoyixie.tju@gmail.com>,
	Kuniyuki Iwashima <kuniyu@google.com>,
	Jakub Kicinski <kuba@kernel.org>
Subject: [PATCH 6.1 0828/1067] xfrm: xfrm_interface: require CAP_NET_ADMIN in the device netns for changelink
Date: Tue, 21 Jul 2026 17:23:49 +0200
Message-ID: <20260721152443.071054133@linuxfoundation.org>
In-Reply-To: <20260721152424.521567757@linuxfoundation.org>
References: <20260721152424.521567757@linuxfoundation.org>
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6.1-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Maoyi Xie <maoyixie.tju@gmail.com>

commit 095515d89b19b6cc19dfcdc846f97403ed1ebce3 upstream.

xfrmi_changelink() operates on at most two netns, dev_net(dev) and the
interface link netns xi->net. They differ once the device is created in
or moved to a netns other than the one the request runs in. The rtnl
changelink path checks CAP_NET_ADMIN only against dev_net(dev), so a
caller privileged there but not in xi->net can rewrite an interface that
lives in xi->net.

Gate xfrmi_changelink() on rtnl_dev_link_net_capable() at its top,
before any attribute is parsed.

Reported-by: Xiao Liang <shaw.leon@gmail.com>
Closes: https://lore.kernel.org/netdev/CABAhCOSzP1vaThGV35_VnsRCb=87_CPjPVsTHbq905k8A+BuUg@mail.gmail.com/
Fixes: f203b76d7809 ("xfrm: Add virtual xfrm interfaces")
Cc: stable@vger.kernel.org
Signed-off-by: Maoyi Xie <maoyixie.tju@gmail.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@google.com>
Link: https://patch.msgid.link/20260612085941.3158249-8-maoyixie.tju@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/xfrm/xfrm_interface_core.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/net/xfrm/xfrm_interface_core.c
+++ b/net/xfrm/xfrm_interface_core.c
@@ -865,6 +865,9 @@ static int xfrmi_changelink(struct net_d
 	struct net *net = xi->net;
 	struct xfrm_if_parms p = {};
 
+	if (!rtnl_dev_link_net_capable(dev, net))
+		return -EPERM;
+
 	xfrmi_netlink_parms(data, &p);
 	if (!p.if_id) {
 		NL_SET_ERR_MSG(extack, "if_id must be non zero");