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authorhannes@stressinduktion.org <hannes@stressinduktion.org>2015-04-01 17:07:44 +0200
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2015-04-29 10:31:46 +0200
commitc91f81773cd4bbebfe744e9ab30a7ce093f9b930 (patch)
treea21775dbb33156bef196464337e9f38059e8f10d /net
parente6250f868ccc8a609c88524a785a6e0d915ad3cb (diff)
downloadlinux-linaro-stable-c91f81773cd4bbebfe744e9ab30a7ce093f9b930.tar.gz
ipv6: protect skb->sk accesses from recursive dereference inside the stack
[ 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@resnulli.us> Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'net')
-rw-r--r--net/core/dev.c4
-rw-r--r--net/core/sock.c19
-rw-r--r--net/ipv6/ip6_output.c3
3 files changed, 24 insertions, 2 deletions
diff --git a/net/core/dev.c b/net/core/dev.c
index f6d8d7fe29ab..73abbd77d72c 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2775,7 +2775,9 @@ 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
/**
diff --git a/net/core/sock.c b/net/core/sock.c
index c8069561bdb7..650dd58ebd05 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -659,6 +659,25 @@ 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.
diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index d7907ecf0b75..066d0b03f2b8 100644
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -555,7 +555,8 @@ 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;