netfilter: implement xt_cgroup cgroup2 path match

This patch implements xt_cgroup path match which matches cgroup2
membership of the associated socket.  The match is recursive and
invertible.

For rationales on introducing another cgroup based match, please refer
to a preceding commit "sock, cgroup: add sock->sk_cgroup".

v3: Folded into xt_cgroup as a new revision interface as suggested by
    Pablo.

v2: Included linux/limits.h from xt_cgroup2.h for PATH_MAX.  Added
    explicit alignment to the priv field.  Both suggested by Jan.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Daniel Wagner <daniel.wagner@bmw-carit.de>
CC: Neil Horman <nhorman@tuxdriver.com>
Cc: Jan Engelhardt <jengelh@inai.de>
Cc: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

diff --git a/include/uapi/linux/netfilter/xt_cgroup.h b/include/uapi/linux/netfilter/xt_cgroup.h
index 577c9e0..1e4b37b 100644 (file)
--- a/include/uapi/linux/netfilter/xt_cgroup.h
+++ b/include/uapi/linux/netfilter/xt_cgroup.h
@@ -2,10 +2,23 @@
 #define _UAPI_XT_CGROUP_H
 
 #include <linux/types.h>
+#include <linux/limits.h>
 
 struct xt_cgroup_info_v0 {
        __u32 id;
        __u32 invert;
 };
 
+struct xt_cgroup_info_v1 {
+       __u8            has_path;
+       __u8            has_classid;
+       __u8            invert_path;
+       __u8            invert_classid;
+       char            path[PATH_MAX];
+       __u32           classid;
+
+       /* kernel internal data */
+       void            *priv __attribute__((aligned(8)));
+};
+
 #endif /* _UAPI_XT_CGROUP_H */

diff --git a/net/netfilter/xt_cgroup.c b/net/netfilter/xt_cgroup.c
index 1730025..a086a91 100644 (file)
--- a/net/netfilter/xt_cgroup.c
+++ b/net/netfilter/xt_cgroup.c
@@ -34,6 +34,37 @@ static int cgroup_mt_check_v0(const struct xt_mtchk_param *par)
        return 0;
 }
 
+static int cgroup_mt_check_v1(const struct xt_mtchk_param *par)
+{
+       struct xt_cgroup_info_v1 *info = par->matchinfo;
+       struct cgroup *cgrp;
+
+       if ((info->invert_path & ~1) || (info->invert_classid & ~1))
+               return -EINVAL;
+
+       if (!info->has_path && !info->has_classid) {
+               pr_info("xt_cgroup: no path or classid specified\n");
+               return -EINVAL;
+       }
+
+       if (info->has_path && info->has_classid) {
+               pr_info("xt_cgroup: both path and classid specified\n");
+               return -EINVAL;
+       }
+
+       if (info->has_path) {
+               cgrp = cgroup_get_from_path(info->path);
+               if (IS_ERR(cgrp)) {
+                       pr_info("xt_cgroup: invalid path, errno=%ld\n",
+                               PTR_ERR(cgrp));
+                       return -EINVAL;
+               }
+               info->priv = cgrp;
+       }
+
+       return 0;
+}
+
 static bool
 cgroup_mt_v0(const struct sk_buff *skb, struct xt_action_param *par)
 {
@@ -46,6 +77,31 @@ cgroup_mt_v0(const struct sk_buff *skb, struct xt_action_param *par)
                info->invert;
 }
 
+static bool cgroup_mt_v1(const struct sk_buff *skb, struct xt_action_param *par)
+{
+       const struct xt_cgroup_info_v1 *info = par->matchinfo;
+       struct sock_cgroup_data *skcd = &skb->sk->sk_cgrp_data;
+       struct cgroup *ancestor = info->priv;
+
+       if (!skb->sk || !sk_fullsock(skb->sk))
+               return false;
+
+       if (ancestor)
+               return cgroup_is_descendant(sock_cgroup_ptr(skcd), ancestor) ^
+                       info->invert_path;
+       else
+               return (info->classid == sock_cgroup_classid(skcd)) ^
+                       info->invert_classid;
+}
+
+static void cgroup_mt_destroy_v1(const struct xt_mtdtor_param *par)
+{
+       struct xt_cgroup_info_v1 *info = par->matchinfo;
+
+       if (info->priv)
+               cgroup_put(info->priv);
+}
+
 static struct xt_match cgroup_mt_reg[] __read_mostly = {
        {
                .name           = "cgroup",
@@ -59,6 +115,19 @@ static struct xt_match cgroup_mt_reg[] __read_mostly = {
                                  (1 << NF_INET_POST_ROUTING) |
                                  (1 << NF_INET_LOCAL_IN),
        },
+       {
+               .name           = "cgroup",
+               .revision       = 1,
+               .family         = NFPROTO_UNSPEC,
+               .checkentry     = cgroup_mt_check_v1,
+               .match          = cgroup_mt_v1,
+               .matchsize      = sizeof(struct xt_cgroup_info_v1),
+               .destroy        = cgroup_mt_destroy_v1,
+               .me             = THIS_MODULE,
+               .hooks          = (1 << NF_INET_LOCAL_OUT) |
+                                 (1 << NF_INET_POST_ROUTING) |
+                                 (1 << NF_INET_LOCAL_IN),
+       },
 };
 
 static int __init cgroup_mt_init(void)