Commit cd4d7263 authored by Ido Schimmel's avatar Ido Schimmel Committed by David S. Miller
Browse files

genetlink: Use internal flags for multicast groups 



As explained in commit e0378187 ("drop_monitor: Require
'CAP_SYS_ADMIN' when joining "events" group"), the "flags" field in the
multicast group structure reuses uAPI flags despite the field not being
exposed to user space. This makes it impossible to extend its use
without adding new uAPI flags, which is inappropriate for internal
kernel checks.

Solve this by adding internal flags (i.e., "GENL_MCAST_*") and convert
the existing users to use them instead of the uAPI flags.

Tested using the reproducers in commit 44ec98ea ("psample: Require
'CAP_NET_ADMIN' when joining "packets" group") and commit e0378187
("drop_monitor: Require 'CAP_SYS_ADMIN' when joining "events" group").

No functional changes intended.

Signed-off-by: default avatarIdo Schimmel <idosch@nvidia.com>
Reviewed-by: default avatarMat Martineau <martineau@kernel.org>
Reviewed-by: default avatarAndy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent f732ba4a

include/net/genetlink.h

+6 −3
Original line number Diff line number Diff line
@@ -8,16 +8,19 @@ 


#define GENLMSG_DEFAULT_SIZE (NLMSG_DEFAULT_SIZE - GENL_HDRLEN)



/* Binding to multicast group requires %CAP_NET_ADMIN */

#define GENL_MCAST_CAP_NET_ADMIN	BIT(0)

/* Binding to multicast group requires %CAP_SYS_ADMIN */

#define GENL_MCAST_CAP_SYS_ADMIN	BIT(1)



/**

 * struct genl_multicast_group - generic netlink multicast group

 * @name: name of the multicast group, names are per-family

 * @flags: GENL_* flags (%GENL_ADMIN_PERM or %GENL_UNS_ADMIN_PERM)

 * @cap_sys_admin: whether %CAP_SYS_ADMIN is required for binding

 * @flags: GENL_MCAST_* flags

 */

struct genl_multicast_group {

	char			name[GENL_NAMSIZ];

	u8			flags;

	u8			cap_sys_admin:1;

};



struct genl_split_ops;

net/core/drop_monitor.c

+1 −1
Original line number Diff line number Diff line
@@ -183,7 +183,7 @@ static struct sk_buff *reset_per_cpu_data(struct per_cpu_dm_data *data) 
}



static const struct genl_multicast_group dropmon_mcgrps[] = {

	{ .name = "events", .cap_sys_admin = 1 },

	{ .name = "events", .flags = GENL_MCAST_CAP_SYS_ADMIN, },

};



static void send_dm_alert(struct work_struct *work)

net/mptcp/pm_netlink.c

+1 −1
Original line number Diff line number Diff line
@@ -1100,7 +1100,7 @@ int mptcp_pm_nl_get_local_id(struct mptcp_sock *msk, struct mptcp_addr_info *skc 
static const struct genl_multicast_group mptcp_pm_mcgrps[] = {

	[MPTCP_PM_CMD_GRP_OFFSET]	= { .name = MPTCP_PM_CMD_GRP_NAME, },

	[MPTCP_PM_EV_GRP_OFFSET]        = { .name = MPTCP_PM_EV_GRP_NAME,

					    .flags = GENL_UNS_ADMIN_PERM,

					    .flags = GENL_MCAST_CAP_NET_ADMIN,

					  },

};

net/netlink/genetlink.c

+2 −2
Original line number Diff line number Diff line
@@ -1829,10 +1829,10 @@ static int genl_bind(struct net *net, int group) 
			continue;



		grp = &family->mcgrps[i];

		if ((grp->flags & GENL_UNS_ADMIN_PERM) &&

		if ((grp->flags & GENL_MCAST_CAP_NET_ADMIN) &&

		    !ns_capable(net->user_ns, CAP_NET_ADMIN))

			ret = -EPERM;

		if (grp->cap_sys_admin &&

		if ((grp->flags & GENL_MCAST_CAP_SYS_ADMIN) &&

		    !ns_capable(net->user_ns, CAP_SYS_ADMIN))

			ret = -EPERM;

net/psample/psample.c

+1 −1
Original line number Diff line number Diff line
@@ -32,7 +32,7 @@ enum psample_nl_multicast_groups { 
static const struct genl_multicast_group psample_nl_mcgrps[] = {

	[PSAMPLE_NL_MCGRP_CONFIG] = { .name = PSAMPLE_NL_MCGRP_CONFIG_NAME },

	[PSAMPLE_NL_MCGRP_SAMPLE] = { .name = PSAMPLE_NL_MCGRP_SAMPLE_NAME,

				      .flags = GENL_UNS_ADMIN_PERM },

				      .flags = GENL_MCAST_CAP_NET_ADMIN, },

};



static struct genl_family psample_nl_family __ro_after_init;