2011-03-10 18:12:18

by Vasily Kulikov

Subject: [PATCH] ipv4: 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 <[email protected]>
---
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

2011-03-15 12:35:54

by Patrick McHardy

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

On 10.03.2011 19:12, Vasiliy Kulikov wrote:
> 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.
>

Applied, thanks.