[PATCH 5.17 083/158] xfrm: fix "disable_policy" flag use when arriving from different devices

Greg Kroah-Hartman
2022-05-23T18:03:09Z

From: Eyal Birger <eyal.birger@gmail.com>

[ Upstream commit e6175a2ed1f18bf2f649625bf725e07adcfa6a28 ]

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: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Reported-by: Shmulik Ladkani <shmulik.ladkani@gmail.com>
Signed-off-by: Eyal Birger <eyal.birger@gmail.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
include/net/ip.h | 1 +
include/net/xfrm.h | 14 +++++++++++++-
net/ipv4/route.c | 23 ++++++++++++++++++-----
3 files changed, 32 insertions(+), 6 deletions(-)

diff --git a/include/net/ip.h b/include/net/ip.h
index b51bae43b0dd..9fba950fdf12 100644
--- a/include/net/ip.h
+++ b/include/net/ip.h
@@ -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;
};
diff --git a/include/net/xfrm.h b/include/net/xfrm.h
index 6fb899ff5afc..d2efddce65d4 100644
--- a/include/net/xfrm.h
+++ b/include/net/xfrm.h
@@ -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);
}

diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index eef07b62b2d8..1cdfac733bd8 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -1721,6 +1721,7 @@ 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;

@@ -1731,8 +1732,12 @@ 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;

@@ -1791,7 +1796,7 @@ 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 */
@@ -1836,6 +1841,10 @@ 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)
@@ -1848,8 +1857,7 @@ 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;
@@ -2224,6 +2232,7 @@ 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. */

@@ -2341,6 +2350,10 @@ 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);
@@ -2355,7 +2368,7 @@ 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;

--
2.35.1