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Date: Sun, 26 Apr 2015 16:15:42 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-kernel@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
stable@...r.kernel.org, Jiri Pirko <jiri@...nulli.us>,
Hannes Frederic Sowa <hannes@...essinduktion.org>,
"David S. Miller" <davem@...emloft.net>
Subject: [PATCH 3.19 11/27] ipv6: protect skb->sk accesses from recursive dereference inside the stack
3.19-stable review patch. If anyone has any objections, please let me know.
------------------
From: "hannes@...essinduktion.org" <hannes@...essinduktion.org>
[ Upstream commit f60e5990d9c1424af9dbca60a23ba2a1c7c1ce90 ]
We should not consult skb->sk for output decisions in xmit recursion
levels > 0 in the stack. Otherwise local socket settings could influence
the result of e.g. tunnel encapsulation process.
ipv6 does not conform with this in three places:
1) ip6_fragment: we do consult ipv6_npinfo for frag_size
2) sk_mc_loop in ipv6 uses skb->sk and checks if we should
loop the packet back to the local socket
3) ip6_skb_dst_mtu could query the settings from the user socket and
force a wrong MTU
Furthermore:
In sk_mc_loop we could potentially land in WARN_ON(1) if we use a
PF_PACKET socket ontop of an IPv6-backed vxlan device.
Reuse xmit_recursion as we are currently only interested in protecting
tunnel devices.
Cc: Jiri Pirko <jiri@...nulli.us>
Signed-off-by: Hannes Frederic Sowa <hannes@...essinduktion.org>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
include/linux/netdevice.h | 6 ++++++
include/net/ip.h | 16 ----------------
include/net/ip6_route.h | 3 ++-
include/net/sock.h | 2 ++
net/core/dev.c | 4 +++-
net/core/sock.c | 19 +++++++++++++++++++
net/ipv6/ip6_output.c | 3 ++-
7 files changed, 34 insertions(+), 19 deletions(-)
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -2159,6 +2159,12 @@ void netdev_freemem(struct net_device *d
void synchronize_net(void);
int init_dummy_netdev(struct net_device *dev);
+DECLARE_PER_CPU(int, xmit_recursion);
+static inline int dev_recursion_level(void)
+{
+ return this_cpu_read(xmit_recursion);
+}
+
struct net_device *dev_get_by_index(struct net *net, int ifindex);
struct net_device *__dev_get_by_index(struct net *net, int ifindex);
struct net_device *dev_get_by_index_rcu(struct net *net, int ifindex);
--- a/include/net/ip.h
+++ b/include/net/ip.h
@@ -453,22 +453,6 @@ static __inline__ void inet_reset_saddr(
#endif
-static inline int sk_mc_loop(struct sock *sk)
-{
- if (!sk)
- return 1;
- switch (sk->sk_family) {
- case AF_INET:
- return inet_sk(sk)->mc_loop;
-#if IS_ENABLED(CONFIG_IPV6)
- case AF_INET6:
- return inet6_sk(sk)->mc_loop;
-#endif
- }
- WARN_ON(1);
- return 1;
-}
-
bool ip_call_ra_chain(struct sk_buff *skb);
/*
--- a/include/net/ip6_route.h
+++ b/include/net/ip6_route.h
@@ -174,7 +174,8 @@ int ip6_fragment(struct sk_buff *skb, in
static inline int ip6_skb_dst_mtu(struct sk_buff *skb)
{
- struct ipv6_pinfo *np = skb->sk ? inet6_sk(skb->sk) : NULL;
+ struct ipv6_pinfo *np = skb->sk && !dev_recursion_level() ?
+ inet6_sk(skb->sk) : NULL;
return (np && np->pmtudisc >= IPV6_PMTUDISC_PROBE) ?
skb_dst(skb)->dev->mtu : dst_mtu(skb_dst(skb));
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -1812,6 +1812,8 @@ struct dst_entry *__sk_dst_check(struct
struct dst_entry *sk_dst_check(struct sock *sk, u32 cookie);
+bool sk_mc_loop(struct sock *sk);
+
static inline bool sk_can_gso(const struct sock *sk)
{
return net_gso_ok(sk->sk_route_caps, sk->sk_gso_type);
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2821,7 +2821,9 @@ static void skb_update_prio(struct sk_bu
#define skb_update_prio(skb)
#endif
-static DEFINE_PER_CPU(int, xmit_recursion);
+DEFINE_PER_CPU(int, xmit_recursion);
+EXPORT_SYMBOL(xmit_recursion);
+
#define RECURSION_LIMIT 10
/**
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -651,6 +651,25 @@ static inline void sock_valbool_flag(str
sock_reset_flag(sk, bit);
}
+bool sk_mc_loop(struct sock *sk)
+{
+ if (dev_recursion_level())
+ return false;
+ if (!sk)
+ return true;
+ switch (sk->sk_family) {
+ case AF_INET:
+ return inet_sk(sk)->mc_loop;
+#if IS_ENABLED(CONFIG_IPV6)
+ case AF_INET6:
+ return inet6_sk(sk)->mc_loop;
+#endif
+ }
+ WARN_ON(1);
+ return true;
+}
+EXPORT_SYMBOL(sk_mc_loop);
+
/*
* This is meant for all protocols to use and covers goings on
* at the socket level. Everything here is generic.
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -541,7 +541,8 @@ int ip6_fragment(struct sk_buff *skb, in
{
struct sk_buff *frag;
struct rt6_info *rt = (struct rt6_info *)skb_dst(skb);
- struct ipv6_pinfo *np = skb->sk ? inet6_sk(skb->sk) : NULL;
+ struct ipv6_pinfo *np = skb->sk && !dev_recursion_level() ?
+ inet6_sk(skb->sk) : NULL;
struct ipv6hdr *tmp_hdr;
struct frag_hdr *fh;
unsigned int mtu, hlen, left, len;
--
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