From: Mark Tomlinson mark.tomlinson@alliedtelesis.co.nz
stable inclusion from linux-4.19.184 commit 0abcfaf058d77aa6450ceb29985e50f72bf6b782
--------------------------------
[ Upstream commit d3d40f237480abf3268956daf18cdc56edd32834 ]
This reverts commit cc00bcaa589914096edef7fb87ca5cee4a166b5c.
This (and the preceding) patch basically re-implemented the RCU mechanisms of patch 784544739a25. That patch was replaced because of the performance problems that it created when replacing tables. Now, we have the same issue: the call to synchronize_rcu() makes replacing tables slower by as much as an order of magnitude.
Prior to using RCU a script calling "iptables" approx. 200 times was taking 1.16s. With RCU this increased to 11.59s.
Revert these patches and fix the issue in a different way.
Signed-off-by: Mark Tomlinson mark.tomlinson@alliedtelesis.co.nz Signed-off-by: Pablo Neira Ayuso pablo@netfilter.org Signed-off-by: Sasha Levin sashal@kernel.org Signed-off-by: Yang Yingliang yangyingliang@huawei.com Signed-off-by: Cheng Jian cj.chengjian@huawei.com --- include/linux/netfilter/x_tables.h | 5 +-- net/ipv4/netfilter/arp_tables.c | 14 ++++----- net/ipv4/netfilter/ip_tables.c | 14 ++++----- net/ipv6/netfilter/ip6_tables.c | 14 ++++----- net/netfilter/x_tables.c | 49 +++++++++++++++++++++--------- 5 files changed, 56 insertions(+), 40 deletions(-)
diff --git a/include/linux/netfilter/x_tables.h b/include/linux/netfilter/x_tables.h index 728d7716bf4f..9077b3ebea08 100644 --- a/include/linux/netfilter/x_tables.h +++ b/include/linux/netfilter/x_tables.h @@ -227,7 +227,7 @@ struct xt_table { unsigned int valid_hooks;
/* Man behind the curtain... */ - struct xt_table_info __rcu *private; + struct xt_table_info *private;
/* Set this to THIS_MODULE if you are a module, otherwise NULL */ struct module *me; @@ -449,9 +449,6 @@ xt_get_per_cpu_counter(struct xt_counters *cnt, unsigned int cpu)
struct nf_hook_ops *xt_hook_ops_alloc(const struct xt_table *, nf_hookfn *);
-struct xt_table_info -*xt_table_get_private_protected(const struct xt_table *table); - #ifdef CONFIG_COMPAT #include <net/compat.h>
diff --git a/net/ipv4/netfilter/arp_tables.c b/net/ipv4/netfilter/arp_tables.c index a2cae543a285..b1106d4507fd 100644 --- a/net/ipv4/netfilter/arp_tables.c +++ b/net/ipv4/netfilter/arp_tables.c @@ -202,7 +202,7 @@ unsigned int arpt_do_table(struct sk_buff *skb,
local_bh_disable(); addend = xt_write_recseq_begin(); - private = rcu_access_pointer(table->private); + private = READ_ONCE(table->private); /* Address dependency. */ cpu = smp_processor_id(); table_base = private->entries; jumpstack = (struct arpt_entry **)private->jumpstack[cpu]; @@ -648,7 +648,7 @@ static struct xt_counters *alloc_counters(const struct xt_table *table) { unsigned int countersize; struct xt_counters *counters; - const struct xt_table_info *private = xt_table_get_private_protected(table); + const struct xt_table_info *private = table->private;
/* We need atomic snapshot of counters: rest doesn't change * (other than comefrom, which userspace doesn't care @@ -672,7 +672,7 @@ static int copy_entries_to_user(unsigned int total_size, unsigned int off, num; const struct arpt_entry *e; struct xt_counters *counters; - struct xt_table_info *private = xt_table_get_private_protected(table); + struct xt_table_info *private = table->private; int ret = 0; void *loc_cpu_entry;
@@ -807,7 +807,7 @@ static int get_info(struct net *net, void __user *user, t = xt_request_find_table_lock(net, NFPROTO_ARP, name); if (!IS_ERR(t)) { struct arpt_getinfo info; - const struct xt_table_info *private = xt_table_get_private_protected(t); + const struct xt_table_info *private = t->private; #ifdef CONFIG_COMPAT struct xt_table_info tmp;
@@ -860,7 +860,7 @@ static int get_entries(struct net *net, struct arpt_get_entries __user *uptr,
t = xt_find_table_lock(net, NFPROTO_ARP, get.name); if (!IS_ERR(t)) { - const struct xt_table_info *private = xt_table_get_private_protected(t); + const struct xt_table_info *private = t->private;
if (get.size == private->size) ret = copy_entries_to_user(private->size, @@ -1019,7 +1019,7 @@ static int do_add_counters(struct net *net, const void __user *user, }
local_bh_disable(); - private = xt_table_get_private_protected(t); + private = t->private; if (private->number != tmp.num_counters) { ret = -EINVAL; goto unlock_up_free; @@ -1356,7 +1356,7 @@ static int compat_copy_entries_to_user(unsigned int total_size, void __user *userptr) { struct xt_counters *counters; - const struct xt_table_info *private = xt_table_get_private_protected(table); + const struct xt_table_info *private = table->private; void __user *pos; unsigned int size; int ret = 0; diff --git a/net/ipv4/netfilter/ip_tables.c b/net/ipv4/netfilter/ip_tables.c index 6672172a7512..2c1d66bef720 100644 --- a/net/ipv4/netfilter/ip_tables.c +++ b/net/ipv4/netfilter/ip_tables.c @@ -261,7 +261,7 @@ ipt_do_table(struct sk_buff *skb, WARN_ON(!(table->valid_hooks & (1 << hook))); local_bh_disable(); addend = xt_write_recseq_begin(); - private = rcu_access_pointer(table->private); + private = READ_ONCE(table->private); /* Address dependency. */ cpu = smp_processor_id(); table_base = private->entries; jumpstack = (struct ipt_entry **)private->jumpstack[cpu]; @@ -794,7 +794,7 @@ static struct xt_counters *alloc_counters(const struct xt_table *table) { unsigned int countersize; struct xt_counters *counters; - const struct xt_table_info *private = xt_table_get_private_protected(table); + const struct xt_table_info *private = table->private;
/* We need atomic snapshot of counters: rest doesn't change (other than comefrom, which userspace doesn't care @@ -818,7 +818,7 @@ copy_entries_to_user(unsigned int total_size, unsigned int off, num; const struct ipt_entry *e; struct xt_counters *counters; - const struct xt_table_info *private = xt_table_get_private_protected(table); + const struct xt_table_info *private = table->private; int ret = 0; const void *loc_cpu_entry;
@@ -968,7 +968,7 @@ static int get_info(struct net *net, void __user *user, t = xt_request_find_table_lock(net, AF_INET, name); if (!IS_ERR(t)) { struct ipt_getinfo info; - const struct xt_table_info *private = xt_table_get_private_protected(t); + const struct xt_table_info *private = t->private; #ifdef CONFIG_COMPAT struct xt_table_info tmp;
@@ -1022,7 +1022,7 @@ get_entries(struct net *net, struct ipt_get_entries __user *uptr,
t = xt_find_table_lock(net, AF_INET, get.name); if (!IS_ERR(t)) { - const struct xt_table_info *private = xt_table_get_private_protected(t); + const struct xt_table_info *private = t->private; if (get.size == private->size) ret = copy_entries_to_user(private->size, t, uptr->entrytable); @@ -1178,7 +1178,7 @@ do_add_counters(struct net *net, const void __user *user, }
local_bh_disable(); - private = xt_table_get_private_protected(t); + private = t->private; if (private->number != tmp.num_counters) { ret = -EINVAL; goto unlock_up_free; @@ -1573,7 +1573,7 @@ compat_copy_entries_to_user(unsigned int total_size, struct xt_table *table, void __user *userptr) { struct xt_counters *counters; - const struct xt_table_info *private = xt_table_get_private_protected(table); + const struct xt_table_info *private = table->private; void __user *pos; unsigned int size; int ret = 0; diff --git a/net/ipv6/netfilter/ip6_tables.c b/net/ipv6/netfilter/ip6_tables.c index 3b067d5a62ee..19eb40355dd1 100644 --- a/net/ipv6/netfilter/ip6_tables.c +++ b/net/ipv6/netfilter/ip6_tables.c @@ -283,7 +283,7 @@ ip6t_do_table(struct sk_buff *skb,
local_bh_disable(); addend = xt_write_recseq_begin(); - private = rcu_access_pointer(table->private); + private = READ_ONCE(table->private); /* Address dependency. */ cpu = smp_processor_id(); table_base = private->entries; jumpstack = (struct ip6t_entry **)private->jumpstack[cpu]; @@ -810,7 +810,7 @@ static struct xt_counters *alloc_counters(const struct xt_table *table) { unsigned int countersize; struct xt_counters *counters; - const struct xt_table_info *private = xt_table_get_private_protected(table); + const struct xt_table_info *private = table->private;
/* We need atomic snapshot of counters: rest doesn't change (other than comefrom, which userspace doesn't care @@ -834,7 +834,7 @@ copy_entries_to_user(unsigned int total_size, unsigned int off, num; const struct ip6t_entry *e; struct xt_counters *counters; - const struct xt_table_info *private = xt_table_get_private_protected(table); + const struct xt_table_info *private = table->private; int ret = 0; const void *loc_cpu_entry;
@@ -984,7 +984,7 @@ static int get_info(struct net *net, void __user *user, t = xt_request_find_table_lock(net, AF_INET6, name); if (!IS_ERR(t)) { struct ip6t_getinfo info; - const struct xt_table_info *private = xt_table_get_private_protected(t); + const struct xt_table_info *private = t->private; #ifdef CONFIG_COMPAT struct xt_table_info tmp;
@@ -1039,7 +1039,7 @@ get_entries(struct net *net, struct ip6t_get_entries __user *uptr,
t = xt_find_table_lock(net, AF_INET6, get.name); if (!IS_ERR(t)) { - struct xt_table_info *private = xt_table_get_private_protected(t); + struct xt_table_info *private = t->private; if (get.size == private->size) ret = copy_entries_to_user(private->size, t, uptr->entrytable); @@ -1194,7 +1194,7 @@ do_add_counters(struct net *net, const void __user *user, unsigned int len, }
local_bh_disable(); - private = xt_table_get_private_protected(t); + private = t->private; if (private->number != tmp.num_counters) { ret = -EINVAL; goto unlock_up_free; @@ -1582,7 +1582,7 @@ compat_copy_entries_to_user(unsigned int total_size, struct xt_table *table, void __user *userptr) { struct xt_counters *counters; - const struct xt_table_info *private = xt_table_get_private_protected(table); + const struct xt_table_info *private = table->private; void __user *pos; unsigned int size; int ret = 0; diff --git a/net/netfilter/x_tables.c b/net/netfilter/x_tables.c index 1314de5f317f..8b83806f4f8c 100644 --- a/net/netfilter/x_tables.c +++ b/net/netfilter/x_tables.c @@ -1356,14 +1356,6 @@ struct xt_counters *xt_counters_alloc(unsigned int counters) } EXPORT_SYMBOL(xt_counters_alloc);
-struct xt_table_info -*xt_table_get_private_protected(const struct xt_table *table) -{ - return rcu_dereference_protected(table->private, - mutex_is_locked(&xt[table->af].mutex)); -} -EXPORT_SYMBOL(xt_table_get_private_protected); - struct xt_table_info * xt_replace_table(struct xt_table *table, unsigned int num_counters, @@ -1371,6 +1363,7 @@ xt_replace_table(struct xt_table *table, int *error) { struct xt_table_info *private; + unsigned int cpu; int ret;
ret = xt_jumpstack_alloc(newinfo); @@ -1380,20 +1373,47 @@ xt_replace_table(struct xt_table *table, }
/* Do the substitution. */ - private = xt_table_get_private_protected(table); + local_bh_disable(); + private = table->private;
/* Check inside lock: is the old number correct? */ if (num_counters != private->number) { pr_debug("num_counters != table->private->number (%u/%u)\n", num_counters, private->number); + local_bh_enable(); *error = -EAGAIN; return NULL; }
newinfo->initial_entries = private->initial_entries; + /* + * Ensure contents of newinfo are visible before assigning to + * private. + */ + smp_wmb(); + table->private = newinfo; + + /* make sure all cpus see new ->private value */ + smp_wmb();
- rcu_assign_pointer(table->private, newinfo); - synchronize_rcu(); + /* + * Even though table entries have now been swapped, other CPU's + * may still be using the old entries... + */ + local_bh_enable(); + + /* ... so wait for even xt_recseq on all cpus */ + for_each_possible_cpu(cpu) { + seqcount_t *s = &per_cpu(xt_recseq, cpu); + u32 seq = raw_read_seqcount(s); + + if (seq & 1) { + do { + cond_resched(); + cpu_relax(); + } while (seq == raw_read_seqcount(s)); + } + }
#ifdef CONFIG_AUDIT if (audit_enabled) { @@ -1434,12 +1454,12 @@ struct xt_table *xt_register_table(struct net *net, }
/* Simplifies replace_table code. */ - rcu_assign_pointer(table->private, bootstrap); + table->private = bootstrap;
if (!xt_replace_table(table, 0, newinfo, &ret)) goto unlock;
- private = xt_table_get_private_protected(table); + private = table->private; pr_debug("table->private->number = %u\n", private->number);
/* save number of initial entries */ @@ -1462,8 +1482,7 @@ void *xt_unregister_table(struct xt_table *table) struct xt_table_info *private;
mutex_lock(&xt[table->af].mutex); - private = xt_table_get_private_protected(table); - RCU_INIT_POINTER(table->private, NULL); + private = table->private; list_del(&table->list); mutex_unlock(&xt[table->af].mutex); kfree(table);