[PATCH] ipv4: netfilter: arp_tables: fix infoleak to userspace

[Vasiliy Kulikov]

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@xxxxxxxxxxxx>
---
 Compile tested.

 net/ipv4/netfilter/arp_tables.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/net/ipv4/netfilter/arp_tables.c b/net/ipv4/netfilter/arp_tables.c
index e95054c..4b5d457 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),
-- 
1.7.0.4

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