| Message ID | 20231220154358.2063280-1-idosch@nvidia.com (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | cd4d7263d58ab98fd4dee876776e4da6c328faa3 |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | [net-next,v2] genetlink: Use internal flags for multicast groups | expand |
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(-)
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>
Hello: This patch was applied to netdev/net-next.git (main) by David S. Miller <davem@davemloft.net>: On Wed, 20 Dec 2023 17:43:58 +0200 you 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. > > [...] Here is the summary with links: - [net-next,v2] genetlink: Use internal flags for multicast groups https://git.kernel.org/netdev/net-next/c/cd4d7263d58a You are awesome, thank you!
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;
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(-)