netfilter: arp_tables: fix infoleak to userspace

Structures ipt_replace, compat_ipt_replace, and xt_get_revision are
copied from userspace.  Fields of these structs that are
zero-terminated strings are not checked.  When they are used as argument
to a format string containing "%s" in request_module(), some sensitive
information is leaked to userspace via argument of spawned modprobe
process.

The first bug was introduced before the git epoch;  the second is
introduced by 6b7d31fc (v2.6.15-rc1);  the third is introduced by
6b7d31fc (v2.6.15-rc1).  To trigger the bug one should have
CAP_NET_ADMIN.

Signed-off-by: Vasiliy Kulikov <segoon@openwall.com>
Signed-off-by: Patrick McHardy <kaber@trash.net>

1 files changed, 3 insertions, 0 deletions

diff --git a/net/ipv4/netfilter/arp_tables.c b/net/ipv4/netfilter/arp_tables.c
index e95054c690c6..4b5d457c2d76 100644
--- a/net/ipv4/netfilter/arp_tables.c
+++ b/net/ipv4/netfilter/arp_tables.c
@@ -1066,6 +1066,7 @@ static int do_replace(struct net *net, const void __user *user,
         /* overflow check */
         if (tmp.num_counters >= INT_MAX / sizeof(struct xt_counters))
                 return -ENOMEM;
+        tmp.name[sizeof(tmp.name)-1] = 0;
 
         newinfo = xt_alloc_table_info(tmp.size);
         if (!newinfo)
@@ -1488,6 +1489,7 @@ static int compat_do_replace(struct net *net, void __user *user,
                 return -ENOMEM;
         if (tmp.num_counters >= INT_MAX / sizeof(struct xt_counters))
                 return -ENOMEM;
+        tmp.name[sizeof(tmp.name)-1] = 0;
 
         newinfo = xt_alloc_table_info(tmp.size);
         if (!newinfo)
@@ -1740,6 +1742,7 @@ static int do_arpt_get_ctl(struct sock *sk, int cmd, void __user *user, int *len
                         ret = -EFAULT;
                         break;
                 }
+                rev.name[sizeof(rev.name)-1] = 0;
 
                 try_then_request_module(xt_find_revision(NFPROTO_ARP, rev.name,
                                                          rev.revision, 1, &ret),