[34-longterm 243/247] netfilter: ip_tables: fix infoleak to userspace

Paul Gortmaker
2011-06-23T17:39:54Z

From: Vasiliy Kulikov <segoon@openwall.com>

-------------------
This is a commit scheduled for the next v2.6.34 longterm release.
If you see a problem with using this for longterm, please comment.
-------------------

commit 78b79876761b86653df89c48a7010b5cbd41a84a 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 and the third bugs were introduced before the git epoch; the
second was introduced in 2722971c (v2.6.17-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: Paul Gortmaker <paul.gortmaker@windriver.com>
---
net/ipv4/netfilter/ip_tables.c | 3 +++
1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/net/ipv4/netfilter/ip_tables.c b/net/ipv4/netfilter/ip_tables.c
index b29c66d..c89ac49 100644
--- a/net/ipv4/netfilter/ip_tables.c
+++ b/net/ipv4/netfilter/ip_tables.c
@@ -1294,6 +1294,7 @@ do_replace(struct net *net, const 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)
@@ -1838,6 +1839,7 @@ compat_do_replace(struct net *net, void __user *user, unsigned int len)
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)
@@ -2067,6 +2069,7 @@ do_ipt_get_ctl(struct sock *sk, int cmd, void __user *user, int *len)
ret = -EFAULT;
break;
}
+ rev.name[sizeof(rev.name)-1] = 0;

if (cmd == IPT_SO_GET_REVISION_TARGET)
target = 1;
--
1.7.4.4