[PATCH 5/6] netfilter: arp_tables: fix infoleak to userspace CVE-2011-1170

paolo.pisati at canonical.com paolo.pisati at canonical.com
Mon Jul 4 09:53:39 UTC 2011

From: Vasiliy Kulikov <segoon at openwall.com>

BugLink: http://bugs.launchpad.net/bugs/801480

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

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

Signed-off-by: Vasiliy Kulikov <segoon at openwall.com>
Signed-off-by: Patrick McHardy <kaber at trash.net>
Signed-off-by: Paolo Pisati <paolo.pisati at canonical.com>
 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 2909c92..da85e92 100644
--- a/net/ipv4/netfilter/arp_tables.c
+++ b/net/ipv4/netfilter/arp_tables.c
@@ -816,6 +816,7 @@ static int do_replace(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)
@@ -930,6 +931,7 @@ static int do_add_counters(void __user *user, unsigned int len)
 	paddc = vmalloc(len);
 	if (!paddc)
 		return -ENOMEM;
+	tmp.name[sizeof(tmp.name)-1] = 0;
 	if (copy_from_user(paddc, user, len) != 0) {
 		ret = -EFAULT;
@@ -1070,6 +1072,7 @@ static int do_arpt_get_ctl(struct sock *sk, int cmd, void __user *user, int *len
 			ret = -EFAULT;
+		rev.name[sizeof(rev.name)-1] = 0;
 		try_then_request_module(xt_find_revision(NF_ARP, rev.name,
 							 rev.revision, 1, &ret),

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