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genetlink: add CAP_NET_ADMIN test for multicast bind

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This is a partial backport of upstream commit 4d54cc32112d ("mptcp:
avoid lock_fast usage in accept path"). It is only a partial backport
because the patch in the link below was erroneously squash-merged into
upstream commit 4d54cc32112d ("mptcp: avoid lock_fast usage in accept
path"). Below is the original patch description from Florian Westphal:

"
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.
"

Link: https://lore.kernel.org/mptcp/20210213000001.379332-8-mathew.j.martineau@linux.intel.com/
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Ido Schimmel 2023-12-11 14:37:38 +02:00 committed by Ksawlii
parent aa26899dd9
commit 284c1d76dd
2 changed files with 33 additions and 0 deletions
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1
include/net/genetlink.h
View file

@ -15,6 +15,7 @@
*/
struct genl_multicast_group {
char name[GENL_NAMSIZ];
u8 flags;
};
struct genl_ops;

32
net/netlink/genetlink.c
View file

@ -1364,11 +1364,43 @@ 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 */