[PATCH v2] netfilter: xt_owner: Add supplementary groups option

[Lukasz Pawelczyk]

The XT_SUPPL_GROUPS flag causes GIDs specified with XT_OWNER_GID to
be also checked in the supplementary groups of a process.

Signed-off-by: Lukasz Pawelczyk <l.pawelc...@samsung.com>
---
 include/uapi/linux/netfilter/xt_owner.h |  1 +
 net/netfilter/xt_owner.c                | 23 ++++++++++++++++++++---
 2 files changed, 21 insertions(+), 3 deletions(-)

diff --git a/include/uapi/linux/netfilter/xt_owner.h 
b/include/uapi/linux/netfilter/xt_owner.h
index fa3ad84957d5..d646f0dc3466 100644
--- a/include/uapi/linux/netfilter/xt_owner.h
+++ b/include/uapi/linux/netfilter/xt_owner.h
@@ -8,6 +8,7 @@ enum {
        XT_OWNER_UID    = 1 << 0,
        XT_OWNER_GID    = 1 << 1,
        XT_OWNER_SOCKET = 1 << 2,
+       XT_SUPPL_GROUPS = 1 << 3,
 };
 
 struct xt_owner_match_info {
diff --git a/net/netfilter/xt_owner.c b/net/netfilter/xt_owner.c
index 46686fb73784..283a1fb5cc52 100644
--- a/net/netfilter/xt_owner.c
+++ b/net/netfilter/xt_owner.c
@@ -91,11 +91,28 @@ owner_mt(const struct sk_buff *skb, struct xt_action_param 
*par)
        }
 
        if (info->match & XT_OWNER_GID) {
+               unsigned int i, match = false;
                kgid_t gid_min = make_kgid(net->user_ns, info->gid_min);
                kgid_t gid_max = make_kgid(net->user_ns, info->gid_max);
-               if ((gid_gte(filp->f_cred->fsgid, gid_min) &&
-                    gid_lte(filp->f_cred->fsgid, gid_max)) ^
-                   !(info->invert & XT_OWNER_GID))
+               struct group_info *gi = filp->f_cred->group_info;
+
+               if (gid_gte(filp->f_cred->fsgid, gid_min) &&
+                   gid_lte(filp->f_cred->fsgid, gid_max))
+                       match = true;
+
+               if (!match && (info->match & XT_SUPPL_GROUPS) && gi) {
+                       for (i = 0; i < gi->ngroups; ++i) {
+                               kgid_t group = gi->gid[i];
+
+                               if (gid_gte(group, gid_min) &&
+                                   gid_lte(group, gid_max)) {
+                                       match = true;
+                                       break;
+                               }
+                       }
+               }
+
+               if (match ^ !(info->invert & XT_OWNER_GID))
                        return false;
        }
 
-- 
2.20.1