net: add validation for the socket syscall protocol argument

commit 79462ad0 upstream.

郭永刚 reported that one could simply crash the kernel as root by
using a simple program:

	int socket_fd;
	struct sockaddr_in addr;
	addr.sin_port = 0;
	addr.sin_addr.s_addr = INADDR_ANY;
	addr.sin_family = 10;

	socket_fd = socket(10,3,0x40000000);
	connect(socket_fd , &addr,16);

AF_INET, AF_INET6 sockets actually only support 8-bit protocol
identifiers. inet_sock's skc_protocol field thus is sized accordingly,
thus larger protocol identifiers simply cut off the higher bits and
store a zero in the protocol fields.

This could lead to e.g. NULL function pointer because as a result of
the cut off inet_num is zero and we call down to inet_autobind, which
is NULL for raw sockets.

kernel: Call Trace:
kernel:  [<ffffffff816db90e>] ? inet_autobind+0x2e/0x70
kernel:  [<ffffffff816db9a4>] inet_dgram_connect+0x54/0x80
kernel:  [<ffffffff81645069>] SYSC_connect+0xd9/0x110
kernel:  [<ffffffff810ac51b>] ? ptrace_notify+0x5b/0x80
kernel:  [<ffffffff810236d8>] ? syscall_trace_enter_phase2+0x108/0x200
kernel:  [<ffffffff81645e0e>] SyS_connect+0xe/0x10
kernel:  [<ffffffff81779515>] tracesys_phase2+0x84/0x89

I found no particular commit which introduced this problem.

CVE: CVE-2015-8543
Cc: Cong Wang <cwang@twopensource.com>
Reported-by: 郭永刚 <guoyonggang@360.cn>
Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
[bwh: Backported to 2.6.32: open-code U8_MAX; adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Willy Tarreau <w@1wt.eu>

include/net/sock.h

@@ -230,6 +230,7 @@ struct sock {
 				sk_no_check  : 2,
 				sk_userlocks : 4,
 				sk_protocol  : 8,
+#define SK_PROTOCOL_MAX ((u8)~0U)
 				sk_type      : 16;
 	kmemcheck_bitfield_end(flags);
 	int			sk_rcvbuf;

net/ax25/af_ax25.c

@@ -805,6 +805,9 @@ static int ax25_create(struct net *net, struct socket *sock, int protocol)
 	struct sock *sk;
 	ax25_cb *ax25;
 
+	if (protocol < 0 || protocol > SK_PROTOCOL_MAX)
+		return -EINVAL;
+
 	if (net != &init_net)
 		return -EAFNOSUPPORT;
 

net/decnet/af_decnet.c

@@ -679,6 +679,9 @@ static int dn_create(struct net *net, struct socket *sock, int protocol)
 {
 	struct sock *sk;
 
+	if (protocol < 0 || protocol > SK_PROTOCOL_MAX)
+		return -EINVAL;
+
 	if (net != &init_net)
 		return -EAFNOSUPPORT;
 

net/ipv4/af_inet.c

@@ -273,6 +273,9 @@ static int inet_create(struct net *net, struct socket *sock, int protocol)
 	int try_loading_module = 0;
 	int err;
 
+	if (protocol < 0 || protocol >= IPPROTO_MAX)
+		return -EINVAL;
+
 	if (unlikely(!inet_ehash_secret))
 		if (sock->type != SOCK_RAW && sock->type != SOCK_DGRAM)
 			build_ehash_secret();

net/ipv6/af_inet6.c

@@ -107,6 +107,9 @@ static int inet6_create(struct net *net, struct socket *sock, int protocol)
 	int try_loading_module = 0;
 	int err;
 
+	if (protocol < 0 || protocol >= IPPROTO_MAX)
+		return -EINVAL;
+
 	if (sock->type != SOCK_RAW &&
 	    sock->type != SOCK_DGRAM &&
 	    !inet_ehash_secret)

net/irda/af_irda.c

@@ -1069,6 +1069,9 @@ static int irda_create(struct net *net, struct socket *sock, int protocol)
 
 	IRDA_DEBUG(2, "%s()\n", __func__);
 
+	if (protocol < 0 || protocol > SK_PROTOCOL_MAX)
+		return -EINVAL;
+
 	if (net != &init_net)
 		return -EAFNOSUPPORT;