| Message ID | 20210120154337.27997-5-fw@strlen.de |
|---|---|
| State | Accepted, archived |
| Commit | edd4b6f8f6ac922a42d03b3a0955ce94bf1ee04b |
| Delegated to: | Matthieu Baerts |
| Headers | show |
| Series | mptcp: netlink event support | expand |
On Wed, 20 Jan 2021, Florian Westphal wrote: > genetlink sets NL_CFG_F_NONROOT_RECV for its netlink socket so anyone can > subscribe to multicast messages. > > rtnetlink doesn't allow this unconditionally, rtnetlink_bind() restricts > bind requests to CAP_NET_ADMIN for a few groups. > > This allows to set GENL_UNS_ADMIN_PERM flag on genl mcast groups to > mandate CAP_NET_ADMIN. > > This will be used by the upcoming mptcp netlink event facility which > exposes the token (mptcp connection identifier) to userspace. > > Signed-off-by: Florian Westphal <fw@strlen.de> > --- > include/net/genetlink.h | 1 + > net/netlink/genetlink.c | 32 ++++++++++++++++++++++++++++++++ > 2 files changed, 33 insertions(+) > Acked-by: Mat Martineau <mathew.j.martineau@linux.intel.com> -- Mat Martineau Intel
diff --git a/include/net/genetlink.h b/include/net/genetlink.h index e55ec1597ce7..7cb3fa8310ed 100644 --- a/include/net/genetlink.h +++ b/include/net/genetlink.h @@ -14,6 +14,7 @@ */ struct genl_multicast_group { char name[GENL_NAMSIZ]; + u8 flags; }; struct genl_ops; diff --git a/net/netlink/genetlink.c b/net/netlink/genetlink.c index c992424e4d63..2d6fdf40df66 100644 --- a/net/netlink/genetlink.c +++ b/net/netlink/genetlink.c @@ -1360,11 +1360,43 @@ static struct genl_family genl_ctrl __ro_after_init = { .netnsok = true, }; +static int genl_bind(struct net *net, int group) +{ + const struct genl_family *family; + unsigned int id; + int ret = 0; + + genl_lock_all(); + + idr_for_each_entry(&genl_fam_idr, family, id) { + const struct genl_multicast_group *grp; + int i; + + if (family->n_mcgrps == 0) + continue; + + i = group - family->mcgrp_offset; + if (i < 0 || i >= family->n_mcgrps) + continue; + + grp = &family->mcgrps[i]; + if ((grp->flags & GENL_UNS_ADMIN_PERM) && + !ns_capable(net->user_ns, CAP_NET_ADMIN)) + ret = -EPERM; + + break; + } + + genl_unlock_all(); + return ret; +} + static int __net_init genl_pernet_init(struct net *net) { struct netlink_kernel_cfg cfg = { .input = genl_rcv, .flags = NL_CFG_F_NONROOT_RECV, + .bind = genl_bind, }; /* we'll bump the group number right afterwards */
genetlink sets NL_CFG_F_NONROOT_RECV for its netlink socket so anyone can subscribe to multicast messages. rtnetlink doesn't allow this unconditionally, rtnetlink_bind() restricts bind requests to CAP_NET_ADMIN for a few groups. This allows to set GENL_UNS_ADMIN_PERM flag on genl mcast groups to mandate CAP_NET_ADMIN. This will be used by the upcoming mptcp netlink event facility which exposes the token (mptcp connection identifier) to userspace. Signed-off-by: Florian Westphal <fw@strlen.de> --- include/net/genetlink.h | 1 + net/netlink/genetlink.c | 32 ++++++++++++++++++++++++++++++++ 2 files changed, 33 insertions(+)