netfilter: ebtables: enforce CAP_NET_ADMIN

normal users are currently allowed to set/modify ebtables rules.
Restrict it to processes with CAP_NET_ADMIN.

Note that this cannot be reproduced with unmodified ebtables binary
because it uses SOCK_RAW.

Signed-off-by: Florian Westphal <fwestphal@astaro.com>
Cc: stable@kernel.org
Signed-off-by: Patrick McHardy <kaber@trash.net>

1 files changed, 6 insertions, 0 deletions

diff --git a/net/bridge/netfilter/ebtables.c b/net/bridge/netfilter/ebtables.c
index bd1c65425d4..0b7f262cd14 100644
--- a/net/bridge/netfilter/ebtables.c
+++ b/net/bridge/netfilter/ebtables.c
@@ -1406,6 +1406,9 @@ static int do_ebt_set_ctl(struct sock *sk,
 {
         int ret;
 
+        if (!capable(CAP_NET_ADMIN))
+                return -EPERM;
+
         switch(cmd) {
         case EBT_SO_SET_ENTRIES:
                 ret = do_replace(sock_net(sk), user, len);
@@ -1425,6 +1428,9 @@ static int do_ebt_get_ctl(struct sock *sk, int cmd, void __user *user, int *len)
         struct ebt_replace tmp;
         struct ebt_table *t;
 
+        if (!capable(CAP_NET_ADMIN))
+                return -EPERM;
+
         if (copy_from_user(&tmp, user, sizeof(tmp)))
                 return -EFAULT;