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[PATCH net-next v2] genetlink: Use internal flags for multicast groups

Ido Schimmel posted 1 patch 4 months, 1 week ago
Patches applied successfully (tree, apply log)
git fetch https://github.com/multipath-tcp/mptcp_net-next tags/patchew/20231220154358.2063280-1-idosch@nvidia.com
Maintainers: "David S. Miller" <davem@davemloft.net>, Eric Dumazet <edumazet@google.com>, Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>, Neil Horman <nhorman@tuxdriver.com>, Matthieu Baerts <matttbe@kernel.org>, Mat Martineau <martineau@kernel.org>, Geliang Tang <geliang.tang@linux.dev>, Yotam Gigi <yotam.gi@gmail.com>
include/net/genetlink.h | 9 ++++++---
net/core/drop_monitor.c | 2 +-
net/mptcp/pm_netlink.c  | 2 +-
net/netlink/genetlink.c | 4 ++--
net/psample/psample.c   | 2 +-
5 files changed, 11 insertions(+), 8 deletions(-)
[PATCH net-next v2] genetlink: Use internal flags for multicast groups
Posted by Ido Schimmel 4 months, 1 week ago 
As explained in commit e03781879a0d ("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 44ec98ea5ea9 ("psample: Require
'CAP_NET_ADMIN' when joining "packets" group") and commit e03781879a0d
("drop_monitor: Require 'CAP_SYS_ADMIN' when joining "events" group").

No functional changes intended.

Signed-off-by: Ido Schimmel <idosch@nvidia.com>
---
v2:
* Add a comment for each flag
---
 include/net/genetlink.h | 9 ++++++---
 net/core/drop_monitor.c | 2 +-
 net/mptcp/pm_netlink.c  | 2 +-
 net/netlink/genetlink.c | 4 ++--
 net/psample/psample.c   | 2 +-
 5 files changed, 11 insertions(+), 8 deletions(-)

diff --git a/include/net/genetlink.h b/include/net/genetlink.h
index 85c63d4f16dd..e61469129402 100644
--- a/include/net/genetlink.h
+++ b/include/net/genetlink.h
@@ -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;
diff --git a/net/core/drop_monitor.c b/net/core/drop_monitor.c
index b240d9aae4a6..b0f221d658be 100644
--- a/net/core/drop_monitor.c
+++ b/net/core/drop_monitor.c
@@ -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)
diff --git a/net/mptcp/pm_netlink.c b/net/mptcp/pm_netlink.c
index bf4d96f6f99a..272e93be1aad 100644
--- a/net/mptcp/pm_netlink.c
+++ b/net/mptcp/pm_netlink.c
@@ -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,
 					  },
 };
 
diff --git a/net/netlink/genetlink.c b/net/netlink/genetlink.c
index c0d15470a10b..8c7af02f8454 100644
--- a/net/netlink/genetlink.c
+++ b/net/netlink/genetlink.c
@@ -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;
 
diff --git a/net/psample/psample.c b/net/psample/psample.c
index c34e902855db..ddd211a151d0 100644
--- a/net/psample/psample.c
+++ b/net/psample/psample.c
@@ -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;
-- 
2.40.1
Re: [PATCH net-next v2] genetlink: Use internal flags for multicast groups
Posted by Andy Shevchenko 4 months, 1 week ago 
On Wed, Dec 20, 2023 at 05:43:58PM +0200, Ido Schimmel wrote:
> As explained in commit e03781879a0d ("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 44ec98ea5ea9 ("psample: Require
> 'CAP_NET_ADMIN' when joining "packets" group") and commit e03781879a0d
> ("drop_monitor: Require 'CAP_SYS_ADMIN' when joining "events" group").
> 
> No functional changes intended.

FWIW,
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

-- 
With Best Regards,
Andy Shevchenko
Re: [PATCH net-next v2] genetlink: Use internal flags for multicast groups
Posted by Mat Martineau 4 months, 1 week ago 
On Wed, 20 Dec 2023, Ido Schimmel wrote:

> As explained in commit e03781879a0d ("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 44ec98ea5ea9 ("psample: Require
> 'CAP_NET_ADMIN' when joining "packets" group") and commit e03781879a0d
> ("drop_monitor: Require 'CAP_SYS_ADMIN' when joining "events" group").
>
> No functional changes intended.
>
> Signed-off-by: Ido Schimmel <idosch@nvidia.com>
> ---
> v2:
> * Add a comment for each flag
> ---
> include/net/genetlink.h | 9 ++++++---
> net/core/drop_monitor.c | 2 +-
> net/mptcp/pm_netlink.c  | 2 +-

Thanks Ido.

For the mptcp change:

Reviewed-by: Mat Martineau <martineau@kernel.org>


> net/netlink/genetlink.c | 4 ++--
> net/psample/psample.c   | 2 +-
> 5 files changed, 11 insertions(+), 8 deletions(-)

Patchew 2.1-devel-0870f84

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