[NETFILTER]: x_tables: struct xt_table_info diet

Instead of using a big array of NR_CPUS entries, we can compute the size
needed at runtime, using nr_cpu_ids

This should save some ram (especially on David's machines where NR_CPUS=4096 :
32 KB can be saved per table, and 64KB for dynamically allocated ones (because
of slab/slub alignements) )

In particular, the 'bootstrap' tables are not any more static (in data
section) but on stack as their size is now very small.

This also should reduce the size used on stack in compat functions
(get_info() declares an automatic variable, that could be bigger than kernel
stack size for big NR_CPUS)

Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/netfilter/x_tables.h b/include/linux/netfilter/x_tables.h
index 9657c4e..e305f2d 100644
--- a/include/linux/netfilter/x_tables.h
+++ b/include/linux/netfilter/x_tables.h
@@ -269,9 +269,12 @@
 	unsigned int underflow[NF_INET_NUMHOOKS];
 
 	/* ipt_entry tables: one per CPU */
-	char *entries[NR_CPUS];
+	/* Note : this field MUST be the last one, see XT_TABLE_INFO_SZ */
+	char *entries[1];
 };
 
+#define XT_TABLE_INFO_SZ (offsetof(struct xt_table_info, entries) \
+			  + nr_cpu_ids * sizeof(char *))
 extern int xt_register_target(struct xt_target *target);
 extern void xt_unregister_target(struct xt_target *target);
 extern int xt_register_targets(struct xt_target *target, unsigned int n);
diff --git a/net/ipv4/netfilter/arp_tables.c b/net/ipv4/netfilter/arp_tables.c
index 2909c92..a21722d 100644
--- a/net/ipv4/netfilter/arp_tables.c
+++ b/net/ipv4/netfilter/arp_tables.c
@@ -811,8 +811,7 @@
 		return -ENOPROTOOPT;
 
 	/* overflow check */
-	if (tmp.size >= (INT_MAX - sizeof(struct xt_table_info)) / NR_CPUS -
-			SMP_CACHE_BYTES)
+	if (tmp.size >= INT_MAX / num_possible_cpus())
 		return -ENOMEM;
 	if (tmp.num_counters >= INT_MAX / sizeof(struct xt_counters))
 		return -ENOMEM;
@@ -1090,7 +1089,7 @@
 {
 	int ret;
 	struct xt_table_info *newinfo;
-	static struct xt_table_info bootstrap
+	struct xt_table_info bootstrap
 		= { 0, 0, 0, { 0 }, { 0 }, { } };
 	void *loc_cpu_entry;
 
diff --git a/net/ipv4/netfilter/ip_tables.c b/net/ipv4/netfilter/ip_tables.c
index ca23c63..87d3692 100644
--- a/net/ipv4/netfilter/ip_tables.c
+++ b/net/ipv4/netfilter/ip_tables.c
@@ -1090,7 +1090,8 @@
 	return 0;
 }
 
-static int compat_calc_entry(struct ipt_entry *e, struct xt_table_info *info,
+static int compat_calc_entry(struct ipt_entry *e,
+		const struct xt_table_info *info,
 		void *base, struct xt_table_info *newinfo)
 {
 	struct ipt_entry_target *t;
@@ -1118,22 +1119,17 @@
 	return 0;
 }
 
-static int compat_table_info(struct xt_table_info *info,
+static int compat_table_info(const struct xt_table_info *info,
 		struct xt_table_info *newinfo)
 {
 	void *loc_cpu_entry;
-	int i;
 
 	if (!newinfo || !info)
 		return -EINVAL;
 
-	memset(newinfo, 0, sizeof(struct xt_table_info));
-	newinfo->size = info->size;
-	newinfo->number = info->number;
-	for (i = 0; i < NF_INET_NUMHOOKS; i++) {
-		newinfo->hook_entry[i] = info->hook_entry[i];
-		newinfo->underflow[i] = info->underflow[i];
-	}
+	/* we dont care about newinfo->entries[] */
+	memcpy(newinfo, info, offsetof(struct xt_table_info, entries));
+	newinfo->initial_entries = 0;
 	loc_cpu_entry = info->entries[raw_smp_processor_id()];
 	return IPT_ENTRY_ITERATE(loc_cpu_entry, info->size,
 			compat_calc_entry, info, loc_cpu_entry, newinfo);
@@ -1327,8 +1323,7 @@
 		return -ENOPROTOOPT;
 
 	/* overflow check */
-	if (tmp.size >= (INT_MAX - sizeof(struct xt_table_info)) / NR_CPUS -
-			SMP_CACHE_BYTES)
+	if (tmp.size >= INT_MAX / num_possible_cpus())
 		return -ENOMEM;
 	if (tmp.num_counters >= INT_MAX / sizeof(struct xt_counters))
 		return -ENOMEM;
@@ -1868,8 +1863,7 @@
 		return -ENOPROTOOPT;
 
 	/* overflow check */
-	if (tmp.size >= (INT_MAX - sizeof(struct xt_table_info)) / NR_CPUS -
-			SMP_CACHE_BYTES)
+	if (tmp.size >= INT_MAX / num_possible_cpus())
 		return -ENOMEM;
 	if (tmp.num_counters >= INT_MAX / sizeof(struct xt_counters))
 		return -ENOMEM;
@@ -2126,7 +2120,7 @@
 {
 	int ret;
 	struct xt_table_info *newinfo;
-	static struct xt_table_info bootstrap
+	struct xt_table_info bootstrap
 		= { 0, 0, 0, { 0 }, { 0 }, { } };
 	void *loc_cpu_entry;
 
diff --git a/net/ipv6/netfilter/ip6_tables.c b/net/ipv6/netfilter/ip6_tables.c
index e1e87ef..e60c1b4 100644
--- a/net/ipv6/netfilter/ip6_tables.c
+++ b/net/ipv6/netfilter/ip6_tables.c
@@ -1042,8 +1042,7 @@
 		return -EFAULT;
 
 	/* overflow check */
-	if (tmp.size >= (INT_MAX - sizeof(struct xt_table_info)) / NR_CPUS -
-			SMP_CACHE_BYTES)
+	if (tmp.size >= INT_MAX / num_possible_cpus())
 		return -ENOMEM;
 	if (tmp.num_counters >= INT_MAX / sizeof(struct xt_counters))
 		return -ENOMEM;
@@ -1339,7 +1338,7 @@
 {
 	int ret;
 	struct xt_table_info *newinfo;
-	static struct xt_table_info bootstrap
+	struct xt_table_info bootstrap
 		= { 0, 0, 0, { 0 }, { 0 }, { } };
 	void *loc_cpu_entry;
 
diff --git a/net/netfilter/x_tables.c b/net/netfilter/x_tables.c
index b6160e4..07bb465 100644
--- a/net/netfilter/x_tables.c
+++ b/net/netfilter/x_tables.c
@@ -499,7 +499,7 @@
 	if ((SMP_ALIGN(size) >> PAGE_SHIFT) + 2 > num_physpages)
 		return NULL;
 
-	newinfo = kzalloc(sizeof(struct xt_table_info), GFP_KERNEL);
+	newinfo = kzalloc(XT_TABLE_INFO_SZ, GFP_KERNEL);
 	if (!newinfo)
 		return NULL;