netfilter: arp_tables: fix infoleak to userspace

commit 42eab94fff18cb1091d3501cd284d6bd6cc9c143 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/net/ipv4/netfilter/arp_tables.c b/net/ipv4/netfilter/arp_tables.c
index 6671485c60c28dc57220014438600df65d2c891d..e468bdd97bf9fac2546eca7f28839fb59a31f33b 100644 (file)
--- a/net/ipv4/netfilter/arp_tables.c
+++ b/net/ipv4/netfilter/arp_tables.c
@@ -1035,6 +1035,7 @@ static int do_replace(struct net *net, void __user *user, unsigned int len)
        /* 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)
@@ -1455,6 +1456,7 @@ 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)
@@ -1710,6 +1712,7 @@ 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(NF_ARP, rev.name,
                                                         rev.revision, 1, &ret),