Commit e6175a2e authored by Eyal Birger's avatar Eyal Birger Committed by Steffen Klassert
Browse files

xfrm: fix "disable_policy" flag use when arriving from different devices 



In IPv4 setting the "disable_policy" flag on a device means no policy
should be enforced for traffic originating from the device. This was
implemented by seting the DST_NOPOLICY flag in the dst based on the
originating device.

However, dsts are cached in nexthops regardless of the originating
devices, in which case, the DST_NOPOLICY flag value may be incorrect.

Consider the following setup:

                     +------------------------------+
                     | ROUTER                       |
  +-------------+    | +-----------------+          |
  | ipsec src   |----|-|ipsec0           |          |
  +-------------+    | |disable_policy=0 |   +----+ |
                     | +-----------------+   |eth1|-|-----
  +-------------+    | +-----------------+   +----+ |
  | noipsec src |----|-|eth0             |          |
  +-------------+    | |disable_policy=1 |          |
                     | +-----------------+          |
                     +------------------------------+

Where ROUTER has a default route towards eth1.

dst entries for traffic arriving from eth0 would have DST_NOPOLICY
and would be cached and therefore can be reused by traffic originating
from ipsec0, skipping policy check.

Fix by setting a IPSKB_NOPOLICY flag in IPCB and observing it instead
of the DST in IN/FWD IPv4 policy checks.

Fixes: 1da177e4 ("Linux-2.6.12-rc2")
Reported-by: default avatarShmulik Ladkani <shmulik.ladkani@gmail.com>
Signed-off-by: default avatarEyal Birger <eyal.birger@gmail.com>
Signed-off-by: default avatarSteffen Klassert <steffen.klassert@secunet.com>
parent 79396934

include/net/ip.h

+1 −0
Original line number Diff line number Diff line
@@ -56,6 +56,7 @@ struct inet_skb_parm { 
#define IPSKB_DOREDIRECT	BIT(5)

#define IPSKB_FRAG_PMTU		BIT(6)

#define IPSKB_L3SLAVE		BIT(7)

#define IPSKB_NOPOLICY		BIT(8)



	u16			frag_max_size;

};

include/net/xfrm.h

+13 −1
Original line number Diff line number Diff line
@@ -1093,6 +1093,18 @@ static inline bool __xfrm_check_nopolicy(struct net *net, struct sk_buff *skb, 
	return false;

}



static inline bool __xfrm_check_dev_nopolicy(struct sk_buff *skb,

					     int dir, unsigned short family)

{

	if (dir != XFRM_POLICY_OUT && family == AF_INET) {

		/* same dst may be used for traffic originating from

		 * devices with different policy settings.

		 */

		return IPCB(skb)->flags & IPSKB_NOPOLICY;

	}

	return skb_dst(skb) && (skb_dst(skb)->flags & DST_NOPOLICY);

}



static inline int __xfrm_policy_check2(struct sock *sk, int dir,

				       struct sk_buff *skb,

				       unsigned int family, int reverse)
@@ -1104,7 +1116,7 @@ static inline int __xfrm_policy_check2(struct sock *sk, int dir, 
		return __xfrm_policy_check(sk, ndir, skb, family);



	return __xfrm_check_nopolicy(net, skb, dir) ||

	       (skb_dst(skb) && (skb_dst(skb)->flags & DST_NOPOLICY)) ||

	       __xfrm_check_dev_nopolicy(skb, dir, family) ||

	       __xfrm_policy_check(sk, ndir, skb, family);

}

net/ipv4/route.c

+18 −5
Original line number Diff line number Diff line
@@ -1726,6 +1726,7 @@ static int ip_route_input_mc(struct sk_buff *skb, __be32 daddr, __be32 saddr, 
	struct in_device *in_dev = __in_dev_get_rcu(dev);

	unsigned int flags = RTCF_MULTICAST;

	struct rtable *rth;

	bool no_policy;

	u32 itag = 0;

	int err;
@@ -1736,8 +1737,12 @@ static int ip_route_input_mc(struct sk_buff *skb, __be32 daddr, __be32 saddr, 
	if (our)

		flags |= RTCF_LOCAL;



	no_policy = IN_DEV_ORCONF(in_dev, NOPOLICY);

	if (no_policy)

		IPCB(skb)->flags |= IPSKB_NOPOLICY;



	rth = rt_dst_alloc(dev_net(dev)->loopback_dev, flags, RTN_MULTICAST,

			   IN_DEV_ORCONF(in_dev, NOPOLICY), false);

			   no_policy, false);

	if (!rth)

		return -ENOBUFS;
@@ -1795,7 +1800,7 @@ static int __mkroute_input(struct sk_buff *skb, 
	struct rtable *rth;

	int err;

	struct in_device *out_dev;

	bool do_cache;

	bool do_cache, no_policy;

	u32 itag = 0;



	/* get a working reference to the output device */
@@ -1840,6 +1845,10 @@ static int __mkroute_input(struct sk_buff *skb, 
		}

	}



	no_policy = IN_DEV_ORCONF(in_dev, NOPOLICY);

	if (no_policy)

		IPCB(skb)->flags |= IPSKB_NOPOLICY;



	fnhe = find_exception(nhc, daddr);

	if (do_cache) {

		if (fnhe)
@@ -1852,8 +1861,7 @@ static int __mkroute_input(struct sk_buff *skb, 
		}

	}



	rth = rt_dst_alloc(out_dev->dev, 0, res->type,

			   IN_DEV_ORCONF(in_dev, NOPOLICY),

	rth = rt_dst_alloc(out_dev->dev, 0, res->type, no_policy,

			   IN_DEV_ORCONF(out_dev, NOXFRM));

	if (!rth) {

		err = -ENOBUFS;
@@ -2228,6 +2236,7 @@ static int ip_route_input_slow(struct sk_buff *skb, __be32 daddr, __be32 saddr, 
	struct rtable	*rth;

	struct flowi4	fl4;

	bool do_cache = true;

	bool no_policy;



	/* IP on this device is disabled. */
@@ -2346,6 +2355,10 @@ out: return err; 
	RT_CACHE_STAT_INC(in_brd);



local_input:

	no_policy = IN_DEV_ORCONF(in_dev, NOPOLICY);

	if (no_policy)

		IPCB(skb)->flags |= IPSKB_NOPOLICY;



	do_cache &= res->fi && !itag;

	if (do_cache) {

		struct fib_nh_common *nhc = FIB_RES_NHC(*res);
@@ -2360,7 +2373,7 @@ out: return err; 


	rth = rt_dst_alloc(ip_rt_get_dev(net, res),

			   flags | RTCF_LOCAL, res->type,

			   IN_DEV_ORCONF(in_dev, NOPOLICY), false);

			   no_policy, false);

	if (!rth)

		goto e_nobufs;