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net: ip_gre: require CAP_NET_ADMIN in the device netns for changelink

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A tunnel changelink() operates on at most two netns, dev_net(dev) and
the tunnel link netns t->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 t->net can rewrite a tunnel that
lives in t->net.

Add rtnl_dev_link_net_capable() next to rtnl_get_net_ns_capable() in
net/core/rtnetlink.c. It requires CAP_NET_ADMIN in the link netns and is
skipped when the link netns is dev_net(dev), where the rtnl path already
checked it. The other patches in this series use the same helper.

Gate ipgre_changelink() and erspan_changelink() with it, at the top of
the op before any attribute is parsed, because the parsers update live
tunnel fields first. ipgre_netlink_parms() sets t->collect_md before
ip_tunnel_changelink() runs.

Commit 8b484efd5c ("ip6: vti: Use ip6_tnl.net in
vti6_siocdevprivate().") added the same check on the ioctl path. This
adds it on RTM_NEWLINK.

Reported-by: Xiao Liang <shaw.leon@gmail.com>
Closes: https://lore.kernel.org/netdev/CABAhCOSzP1vaThGV35_VnsRCb=87_CPjPVsTHbq905k8A+BuUg@mail.gmail.com/
Fixes: b57708add3 ("gre: add x-netns support")
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/20260612085941.3158249-2-maoyixie.tju@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Maoyi Xie
2026-06-12 16:59:35 +08:00
committed by Jakub Kicinski
parent e586644d0a
commit 8165f7ff57
3 changed files with 16 additions and 0 deletions
Download Patch File Download Diff File Expand all files Collapse all files

2
include/net/rtnetlink.h
View File

@@ -256,6 +256,8 @@ int rtnl_configure_link(struct net_device *dev, const struct ifinfomsg *ifm,
int rtnl_nla_parse_ifinfomsg(struct nlattr **tb, const struct nlattr *nla_peer,
struct netlink_ext_ack *exterr);
struct net *rtnl_get_net_ns_capable(struct sock *sk, int netnsid);
bool rtnl_dev_link_net_capable(const struct net_device *dev,
const struct net *link_net);
#define MODULE_ALIAS_RTNL_LINK(kind) MODULE_ALIAS("rtnl-link-" kind)

8
net/core/rtnetlink.c
View File

@@ -2438,6 +2438,14 @@ struct net *rtnl_get_net_ns_capable(struct sock *sk, int netnsid)
}
EXPORT_SYMBOL_GPL(rtnl_get_net_ns_capable);
bool rtnl_dev_link_net_capable(const struct net_device *dev,
const struct net *link_net)
{
return net_eq(link_net, dev_net(dev)) ||
ns_capable(link_net->user_ns, CAP_NET_ADMIN);
}
EXPORT_SYMBOL_GPL(rtnl_dev_link_net_capable);
static int rtnl_valid_dump_ifinfo_req(const struct nlmsghdr *nlh,
bool strict_check, struct nlattr **tb,
struct netlink_ext_ack *extack)

6
net/ipv4/ip_gre.c
View File

@@ -1457,6 +1457,9 @@ static int ipgre_changelink(struct net_device *dev, struct nlattr *tb[],
__u32 fwmark = t->fwmark;
int err;
if (!rtnl_dev_link_net_capable(dev, t->net))
return -EPERM;
err = ipgre_newlink_encap_setup(dev, data);
if (err)
return err;
@@ -1486,6 +1489,9 @@ static int erspan_changelink(struct net_device *dev, struct nlattr *tb[],
__u32 fwmark = t->fwmark;
int err;
if (!rtnl_dev_link_net_capable(dev, t->net))
return -EPERM;
err = ipgre_newlink_encap_setup(dev, data);
if (err)
return err;