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ipv6: protect skb->sk accesses from recursive dereference inside the stack

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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@resnulli.us>
Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
hannes@stressinduktion.org 2015-04-01 17:07:44 +02:00 committed by David S. Miller
parent 576b7cd2f6
commit f60e5990d9
7 changed files with 34 additions and 19 deletions
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6
include/linux/netdevice.h
View File

@ -2185,6 +2185,12 @@ void netdev_freemem(struct net_device *dev);
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);

16
include/net/ip.h
View File

@ -453,22 +453,6 @@ static __inline__ void inet_reset_saddr(struct sock *sk)
#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);
/*

3
include/net/ip6_route.h
View File

@ -174,7 +174,8 @@ int ip6_fragment(struct sk_buff *skb, int (*output)(struct sk_buff *));
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));

2
include/net/sock.h
View File

@ -1762,6 +1762,8 @@ struct dst_entry *__sk_dst_check(struct sock *sk, u32 cookie);
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);

4
net/core/dev.c
View File

@ -2848,7 +2848,9 @@ static void skb_update_prio(struct sk_buff *skb)
#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
/**

19
net/core/sock.c
View File

@ -653,6 +653,25 @@ static inline void sock_valbool_flag(struct sock *sk, int bit, int valbool)
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.

3
net/ipv6/ip6_output.c
View File

@ -542,7 +542,8 @@ int ip6_fragment(struct sk_buff *skb, int (*output)(struct sk_buff *))
{
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;