linux-kernel - [PATCH 4.9 28/92] ipv6: Fix SO_REUSEPORT UDP socket with implicit sk

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Fri,  9 Feb 2018 14:38:57 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Martin KaFai Lau <kafai@...com>,
        "David S. Miller" <davem@...emloft.net>
Subject: [PATCH 4.9 28/92] ipv6: Fix SO_REUSEPORT UDP socket with implicit sk_ipv6only

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Martin KaFai Lau <kafai@...com>

[ Upstream commit 7ece54a60ee2ba7a386308cae73c790bd580589c ]

If a sk_v6_rcv_saddr is !IPV6_ADDR_ANY and !IPV6_ADDR_MAPPED, it
implicitly implies it is an ipv6only socket.  However, in inet6_bind(),
this addr_type checking and setting sk->sk_ipv6only to 1 are only done
after sk->sk_prot->get_port(sk, snum) has been completed successfully.

This inconsistency between sk_v6_rcv_saddr and sk_ipv6only confuses
the 'get_port()'.

In particular, when binding SO_REUSEPORT UDP sockets,
udp_reuseport_add_sock(sk,...) is called.  udp_reuseport_add_sock()
checks "ipv6_only_sock(sk2) == ipv6_only_sock(sk)" before adding sk to
sk2->sk_reuseport_cb.  In this case, ipv6_only_sock(sk2) could be
1 while ipv6_only_sock(sk) is still 0 here.  The end result is,
reuseport_alloc(sk) is called instead of adding sk to the existing
sk2->sk_reuseport_cb.

It can be reproduced by binding two SO_REUSEPORT UDP sockets on an
IPv6 address (!ANY and !MAPPED).  Only one of the socket will
receive packet.

The fix is to set the implicit sk_ipv6only before calling get_port().
The original sk_ipv6only has to be saved such that it can be restored
in case get_port() failed.  The situation is similar to the
inet_reset_saddr(sk) after get_port() has failed.

Thanks to Calvin Owens <calvinowens@...com> who created an easy
reproduction which leads to a fix.

Fixes: e32ea7e74727 ("soreuseport: fast reuseport UDP socket selection")
Signed-off-by: Martin KaFai Lau <kafai@...com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 net/ipv6/af_inet6.c |   11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

--- a/net/ipv6/af_inet6.c
+++ b/net/ipv6/af_inet6.c
@@ -274,6 +274,7 @@ int inet6_bind(struct socket *sock, stru
 	struct net *net = sock_net(sk);
 	__be32 v4addr = 0;
 	unsigned short snum;
+	bool saved_ipv6only;
 	int addr_type = 0;
 	int err = 0;

@@ -378,19 +379,21 @@ int inet6_bind(struct socket *sock, stru
 	if (!(addr_type & IPV6_ADDR_MULTICAST))
 		np->saddr = addr->sin6_addr;

+	saved_ipv6only = sk->sk_ipv6only;
+	if (addr_type != IPV6_ADDR_ANY && addr_type != IPV6_ADDR_MAPPED)
+		sk->sk_ipv6only = 1;
+
 	/* Make sure we are allowed to bind here. */
 	if ((snum || !inet->bind_address_no_port) &&
 	    sk->sk_prot->get_port(sk, snum)) {
+		sk->sk_ipv6only = saved_ipv6only;
 		inet_reset_saddr(sk);
 		err = -EADDRINUSE;
 		goto out;
 	}

-	if (addr_type != IPV6_ADDR_ANY) {
+	if (addr_type != IPV6_ADDR_ANY)
 		sk->sk_userlocks |= SOCK_BINDADDR_LOCK;
-		if (addr_type != IPV6_ADDR_MAPPED)
-			sk->sk_ipv6only = 1;
-	}
 	if (snum)
 		sk->sk_userlocks |= SOCK_BINDPORT_LOCK;
 	inet->inet_sport = htons(inet->inet_num);