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([2a02:2121:806:2ce1:42d9:28ba:7989:a157]) by smtp.gmail.com with ESMTPSA id 2adb3069b0e04-5a2963fa304sm394953e87.27.2026.03.24.01.09.31 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 24 Mar 2026 01:09:32 -0700 (PDT) From: Nikolaos Gkarlis To: netdev@vger.kernel.org Cc: Nikolaos Gkarlis Subject: [PATCH] rtnetlink: add missing netlink_ns_capable() check for peer netns Date: Tue, 24 Mar 2026 09:07:30 +0100 Message-Id: <20260324080730.4051666-1-nickgarlis@gmail.com> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit rtnl_newlink() lacks a CAP_NET_ADMIN capability check on the peer network namespace when creating paired devices (veth, vxcan, netkit). This allows an unprivileged user with a user namespace to create interfaces in arbitrary network namespaces, including init_net. Add a netlink_ns_capable() check for CAP_NET_ADMIN in the peer namespace before allowing device creation to proceed. Fixes: 48327566769a ("rtnetlink: fix double call of rtnl_link_get_net_ifla()") Reported-by: Nikolaos Gkarlis Signed-off-by: Nikolaos Gkarlis --- net/core/rtnetlink.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c index 576d5ec3bb36..f3a7d6dbd713 100644 --- a/net/core/rtnetlink.c +++ b/net/core/rtnetlink.c @@ -4030,8 +4030,15 @@ static int rtnl_newlink(struct sk_buff *skb, struct nlmsghdr *nlh, ret = PTR_ERR(peer_net); goto put_ops; } - if (peer_net) + if (peer_net) { + if (!netlink_ns_capable(skb, peer_net->user_ns, + CAP_NET_ADMIN)) { + put_net(peer_net); + ret = -EPERM; + goto put_ops; + } rtnl_nets_add(&rtnl_nets, peer_net); + } } } -- 2.34.1