net: Revert recent Spectre-v1 patches.

This reverts:

50d52586 ("net: core: Fix Spectre v1 vulnerability")
d686026b ("phonet: af_phonet: Fix Spectre v1 vulnerability")
a95386f0 ("nfc: af_nfc: Fix Spectre v1 vulnerability")
a3ac5817 ("can: af_can: Fix Spectre v1 vulnerability")

After some discussion with Alexei Starovoitov these all seem to
be completely unnecessary.
Signed-off-by: David S. Miller <davem@davemloft.net>

net/can/af_can.c

@@ -59,7 +59,6 @@
 #include <linux/can/core.h>
 #include <linux/can/skb.h>
 #include <linux/ratelimit.h>
-#include <linux/nospec.h>
 #include <net/net_namespace.h>
 #include <net/sock.h>
 
@@ -137,7 +136,6 @@ static int can_create(struct net *net, struct socket *sock, int protocol,
 
 	if (protocol < 0 || protocol >= CAN_NPROTO)
 		return -EINVAL;
-	protocol = array_index_nospec(protocol, CAN_NPROTO);
 
 	cp = can_get_proto(protocol);
 

net/core/filter.c

@@ -73,7 +73,6 @@
 #include <linux/seg6_local.h>
 #include <net/seg6.h>
 #include <net/seg6_local.h>
-#include <linux/nospec.h>
 
 /**
  *	sk_filter_trim_cap - run a packet through a socket filter
@@ -1039,7 +1038,6 @@ static int bpf_check_classic(const struct sock_filter *filter,
 	bool anc_found;
 	int pc;
 
-	flen = array_index_nospec(flen, BPF_MAXINSNS + 1);
 	/* Check the filter code now */
 	for (pc = 0; pc < flen; pc++) {
 		const struct sock_filter *ftest = &filter[pc];

net/nfc/af_nfc.c

@@ -21,7 +21,6 @@
 
 #include <linux/nfc.h>
 #include <linux/module.h>
-#include <linux/nospec.h>
 
 #include "nfc.h"
 
@@ -38,7 +37,6 @@ static int nfc_sock_create(struct net *net, struct socket *sock, int proto,
 
 	if (proto < 0 || proto >= NFC_SOCKPROTO_MAX)
 		return -EINVAL;
-	proto = array_index_nospec(proto, NFC_SOCKPROTO_MAX);
 
 	read_lock(&proto_tab_lock);
 	if (proto_tab[proto] &&	try_module_get(proto_tab[proto]->owner)) {

net/phonet/af_phonet.c

@@ -34,8 +34,6 @@
 #include <net/phonet/phonet.h>
 #include <net/phonet/pn_dev.h>
 
-#include <linux/nospec.h>
-
 /* Transport protocol registration */
 static const struct phonet_protocol *proto_tab[PHONET_NPROTO] __read_mostly;
 
@@ -45,7 +43,6 @@ static const struct phonet_protocol *phonet_proto_get(unsigned int protocol)
 
 	if (protocol >= PHONET_NPROTO)
 		return NULL;
-	protocol = array_index_nospec(protocol, PHONET_NPROTO);
 
 	rcu_read_lock();
 	pp = rcu_dereference(proto_tab[protocol]);