Am 06.11.2010 15:39, schrieb Vasiliy Kulikov:

On Mon, Nov 01, 2010 at 10:14 +0100, walter harms wrote:

quoted

Vasiliy Kulikov schrieb:

quoted

packet_getname_spkt() doesn't initialize all members of sa_data field of
sockaddr struct if strlen(dev->name) < 13.  This structure is then copied
to userland.  It leads to leaking of contents of kernel stack memory.
We have to fully fill sa_data with strncpy() instead of strlcpy().

The same with packet_getname(): it doesn't initialize sll_pkttype field of
sockaddr_ll.  Set it to zero.

Signed-off-by: Vasiliy Kulikov <redacted>
---
 net/packet/af_packet.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index 3616f27..0856a13 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c

@@ -1719,7 +1719,7 @@ static int packet_getname_spkt(struct socket *sock, struct sockaddr *uaddr,
 	rcu_read_lock();
 	dev = dev_get_by_index_rcu(sock_net(sk), pkt_sk(sk)->ifindex);
 	if (dev)
-		strlcpy(uaddr->sa_data, dev->name, 15);
+		strncpy(uaddr->sa_data, dev->name, 14);
 	else
 		memset(uaddr->sa_data, 0, 14);

if i understand the code correcly the max size for dev->name is IFNAMSIZ.

For dev->name - IFNAMSIZ, for uaddr->sa_data - 14.

did not notice, since uaddr->sa_data should take dev->name this does no look very
clever. How is the size of  sa_data defined ? Would it hurt when some uses IFNAMSIZ here ?
Perhaps someone who know more about the network stack can figure out what is actualy done
with uaddr->sa_data.

looks like a can of worms.


In packet_bind_spkt() they will copy a char[15], obviously it is a real problem.

re,
 wh

quoted

You can simply that part:

memset(uaddr->sa_data, 0, IFNAMSIZ);
dev = dev_get_by_index_rcu(sock_net(sk), pkt_sk(sk)->ifindex);
if (dev)
	strlcpy(uaddr->sa_data, dev->name, IFNAMSIZ);

This will overflow uaddr->sa_data.  Also I don't see any difficulty to
fill the array only once.

quoted

you should send that as separate patch.
re,
 wh

quoted

 	rcu_read_unlock();

@@ -1742,6 +1742,7 @@ static int packet_getname(struct socket *sock, struct sockaddr *uaddr,
 	sll->sll_family = AF_PACKET;
 	sll->sll_ifindex = po->ifindex;
 	sll->sll_protocol = po->num;
+	sll->sll_pkttype = 0;
 	rcu_read_lock();
 	dev = dev_get_by_index_rcu(sock_net(sk), po->ifindex);
 	if (dev) {

Thanks,