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[85.165.210.26]) by smtp.gmail.com with ESMTPSA id 2adb3069b0e04-5a2b1456aa2sm49636e87.68.2026.03.27.15.12.32 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 27 Mar 2026 15:12:34 -0700 (PDT) From: Nikolaos Gkarlis To: netdev@vger.kernel.org Cc: kuba@kernel.org, nickgarlis@gmail.com, kuniyu@google.com Subject: [PATCH net v2] rtnetlink: add missing netlink_ns_capable() check for peer netns Date: Fri, 27 Mar 2026 23:12:03 +0100 Message-Id: <20260327221203.430454-1-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: 81adee47dfb6 ("net: Support specifying the network namespace upon device creation.") Signed-off-by: Nikolaos Gkarlis --- v2: - Removed "Reported-by" tag - Fixed "Fixes" tag with the help of Kuniyuki Iwashima (thanks !) 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 fae8034efbf..ee7d9d65b2c 100644 --- a/net/core/rtnetlink.c +++ b/net/core/rtnetlink.c @@ -4059,8 +4059,15 @@ 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