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Commit f4dc7771 authored by Florian Westphal's avatar Florian Westphal Committed by Pablo Neira Ayuso
Browse files

netfilter: x_tables: speed up jump target validation 



The dummy ruleset I used to test the original validation change was broken,
most rules were unreachable and were not tested by mark_source_chains().

In some cases rulesets that used to load in a few seconds now require
several minutes.

sample ruleset that shows the behaviour:

echo "*filter"
for i in $(seq 0 100000);do
        printf ":chain_%06x - [0:0]\n" $i
done
for i in $(seq 0 100000);do
   printf -- "-A INPUT -j chain_%06x\n" $i
   printf -- "-A INPUT -j chain_%06x\n" $i
   printf -- "-A INPUT -j chain_%06x\n" $i
done
echo COMMIT

[ pipe result into iptables-restore ]

This ruleset will be about 74mbyte in size, with ~500k searches
though all 500k[1] rule entries. iptables-restore will take forever
(gave up after 10 minutes)

Instead of always searching the entire blob for a match, fill an
array with the start offsets of every single ipt_entry struct,
then do a binary search to check if the jump target is present or not.

After this change ruleset restore times get again close to what one
gets when reverting 36472341 (~3 seconds on my workstation).

[1] every user-defined rule gets an implicit RETURN, so we get
300k jumps + 100k userchains + 100k returns -> 500k rule entries

Fixes: 36472341 ("netfilter: x_tables: validate targets of jumps")
Reported-by: default avatarJeff Wu <wujiafu@gmail.com>
Tested-by: default avatarJeff Wu <wujiafu@gmail.com>
Signed-off-by: default avatarFlorian Westphal <fw@strlen.de>
Signed-off-by: default avatarPablo Neira Ayuso <pablo@netfilter.org>
parent 3101e0fc

include/linux/netfilter/x_tables.h

+4 −0
Original line number Diff line number Diff line
@@ -250,6 +250,10 @@ int xt_check_entry_offsets(const void *base, const char *elems, 
			   unsigned int target_offset,

			   unsigned int next_offset);



unsigned int *xt_alloc_entry_offsets(unsigned int size);

bool xt_find_jump_offset(const unsigned int *offsets,

			 unsigned int target, unsigned int size);



int xt_check_match(struct xt_mtchk_param *, unsigned int size, u_int8_t proto,

		   bool inv_proto);

int xt_check_target(struct xt_tgchk_param *, unsigned int size, u_int8_t proto,

net/ipv4/netfilter/arp_tables.c

+25 −22
Original line number Diff line number Diff line
@@ -299,23 +299,12 @@ static inline bool unconditional(const struct arpt_entry *e) 
	       memcmp(&e->arp, &uncond, sizeof(uncond)) == 0;

}



static bool find_jump_target(const struct xt_table_info *t,

			     const struct arpt_entry *target)

{

	struct arpt_entry *iter;



	xt_entry_foreach(iter, t->entries, t->size) {

		 if (iter == target)

			return true;

	}

	return false;

}



/* Figures out from what hook each rule can be called: returns 0 if

 * there are loops.  Puts hook bitmask in comefrom.

 */

static int mark_source_chains(const struct xt_table_info *newinfo,

			      unsigned int valid_hooks, void *entry0)

			      unsigned int valid_hooks, void *entry0,

			      unsigned int *offsets)

{

	unsigned int hook;
@@ -388,10 +377,11 @@ static int mark_source_chains(const struct xt_table_info *newinfo, 
					   XT_STANDARD_TARGET) == 0 &&

				    newpos >= 0) {

					/* This a jump; chase it. */

					if (!xt_find_jump_offset(offsets, newpos,

								 newinfo->number))

						return 0;

					e = (struct arpt_entry *)

						(entry0 + newpos);

					if (!find_jump_target(newinfo, e))

						return 0;

				} else {

					/* ... this is a fallthru */

					newpos = pos + e->next_offset;
@@ -543,6 +533,7 @@ static int translate_table(struct xt_table_info *newinfo, void *entry0, 
			   const struct arpt_replace *repl)

{

	struct arpt_entry *iter;

	unsigned int *offsets;

	unsigned int i;

	int ret = 0;
@@ -555,6 +546,9 @@ static int translate_table(struct xt_table_info *newinfo, void *entry0, 
		newinfo->underflow[i] = 0xFFFFFFFF;

	}



	offsets = xt_alloc_entry_offsets(newinfo->number);

	if (!offsets)

		return -ENOMEM;

	i = 0;



	/* Walk through entries, checking offsets. */
@@ -565,17 +559,20 @@ static int translate_table(struct xt_table_info *newinfo, void *entry0, 
						 repl->underflow,

						 repl->valid_hooks);

		if (ret != 0)

			break;

			goto out_free;

		if (i < repl->num_entries)

			offsets[i] = (void *)iter - entry0;

		++i;

		if (strcmp(arpt_get_target(iter)->u.user.name,

		    XT_ERROR_TARGET) == 0)

			++newinfo->stacksize;

	}

	if (ret != 0)

		return ret;

		goto out_free;



	ret = -EINVAL;

	if (i != repl->num_entries)

		return -EINVAL;

		goto out_free;



	/* Check hooks all assigned */

	for (i = 0; i < NF_ARP_NUMHOOKS; i++) {
@@ -583,13 +580,16 @@ static int translate_table(struct xt_table_info *newinfo, void *entry0, 
		if (!(repl->valid_hooks & (1 << i)))

			continue;

		if (newinfo->hook_entry[i] == 0xFFFFFFFF)

			return -EINVAL;

			goto out_free;

		if (newinfo->underflow[i] == 0xFFFFFFFF)

			return -EINVAL;

			goto out_free;

	}



	if (!mark_source_chains(newinfo, repl->valid_hooks, entry0))

		return -ELOOP;

	if (!mark_source_chains(newinfo, repl->valid_hooks, entry0, offsets)) {

		ret = -ELOOP;

		goto out_free;

	}

	kvfree(offsets);



	/* Finally, each sanity check must pass */

	i = 0;
@@ -609,6 +609,9 @@ static int translate_table(struct xt_table_info *newinfo, void *entry0, 
		return ret;

	}



	return ret;

 out_free:

	kvfree(offsets);

	return ret;

}

net/ipv4/netfilter/ip_tables.c

+24 −21
Original line number Diff line number Diff line
@@ -373,23 +373,12 @@ ipt_do_table(struct sk_buff *skb, 
	else return verdict;

}



static bool find_jump_target(const struct xt_table_info *t,

			     const struct ipt_entry *target)

{

	struct ipt_entry *iter;



	xt_entry_foreach(iter, t->entries, t->size) {

		 if (iter == target)

			return true;

	}

	return false;

}



/* Figures out from what hook each rule can be called: returns 0 if

   there are loops.  Puts hook bitmask in comefrom. */

static int

mark_source_chains(const struct xt_table_info *newinfo,

		   unsigned int valid_hooks, void *entry0)

		   unsigned int valid_hooks, void *entry0,

		   unsigned int *offsets)

{

	unsigned int hook;
@@ -458,10 +447,11 @@ mark_source_chains(const struct xt_table_info *newinfo, 
					   XT_STANDARD_TARGET) == 0 &&

				    newpos >= 0) {

					/* This a jump; chase it. */

					if (!xt_find_jump_offset(offsets, newpos,

								 newinfo->number))

						return 0;

					e = (struct ipt_entry *)

						(entry0 + newpos);

					if (!find_jump_target(newinfo, e))

						return 0;

				} else {

					/* ... this is a fallthru */

					newpos = pos + e->next_offset;
@@ -694,6 +684,7 @@ translate_table(struct net *net, struct xt_table_info *newinfo, void *entry0, 
		const struct ipt_replace *repl)

{

	struct ipt_entry *iter;

	unsigned int *offsets;

	unsigned int i;

	int ret = 0;
@@ -706,6 +697,9 @@ translate_table(struct net *net, struct xt_table_info *newinfo, void *entry0, 
		newinfo->underflow[i] = 0xFFFFFFFF;

	}



	offsets = xt_alloc_entry_offsets(newinfo->number);

	if (!offsets)

		return -ENOMEM;

	i = 0;

	/* Walk through entries, checking offsets. */

	xt_entry_foreach(iter, entry0, newinfo->size) {
@@ -715,15 +709,18 @@ translate_table(struct net *net, struct xt_table_info *newinfo, void *entry0, 
						 repl->underflow,

						 repl->valid_hooks);

		if (ret != 0)

			return ret;

			goto out_free;

		if (i < repl->num_entries)

			offsets[i] = (void *)iter - entry0;

		++i;

		if (strcmp(ipt_get_target(iter)->u.user.name,

		    XT_ERROR_TARGET) == 0)

			++newinfo->stacksize;

	}



	ret = -EINVAL;

	if (i != repl->num_entries)

		return -EINVAL;

		goto out_free;



	/* Check hooks all assigned */

	for (i = 0; i < NF_INET_NUMHOOKS; i++) {
@@ -731,13 +728,16 @@ translate_table(struct net *net, struct xt_table_info *newinfo, void *entry0, 
		if (!(repl->valid_hooks & (1 << i)))

			continue;

		if (newinfo->hook_entry[i] == 0xFFFFFFFF)

			return -EINVAL;

			goto out_free;

		if (newinfo->underflow[i] == 0xFFFFFFFF)

			return -EINVAL;

			goto out_free;

	}



	if (!mark_source_chains(newinfo, repl->valid_hooks, entry0))

		return -ELOOP;

	if (!mark_source_chains(newinfo, repl->valid_hooks, entry0, offsets)) {

		ret = -ELOOP;

		goto out_free;

	}

	kvfree(offsets);



	/* Finally, each sanity check must pass */

	i = 0;
@@ -757,6 +757,9 @@ translate_table(struct net *net, struct xt_table_info *newinfo, void *entry0, 
		return ret;

	}



	return ret;

 out_free:

	kvfree(offsets);

	return ret;

}

net/ipv6/netfilter/ip6_tables.c

+24 −21
Original line number Diff line number Diff line
@@ -402,23 +402,12 @@ ip6t_do_table(struct sk_buff *skb, 
	else return verdict;

}



static bool find_jump_target(const struct xt_table_info *t,

			     const struct ip6t_entry *target)

{

	struct ip6t_entry *iter;



	xt_entry_foreach(iter, t->entries, t->size) {

		 if (iter == target)

			return true;

	}

	return false;

}



/* Figures out from what hook each rule can be called: returns 0 if

   there are loops.  Puts hook bitmask in comefrom. */

static int

mark_source_chains(const struct xt_table_info *newinfo,

		   unsigned int valid_hooks, void *entry0)

		   unsigned int valid_hooks, void *entry0,

		   unsigned int *offsets)

{

	unsigned int hook;
@@ -487,10 +476,11 @@ mark_source_chains(const struct xt_table_info *newinfo, 
					   XT_STANDARD_TARGET) == 0 &&

				    newpos >= 0) {

					/* This a jump; chase it. */

					if (!xt_find_jump_offset(offsets, newpos,

								 newinfo->number))

						return 0;

					e = (struct ip6t_entry *)

						(entry0 + newpos);

					if (!find_jump_target(newinfo, e))

						return 0;

				} else {

					/* ... this is a fallthru */

					newpos = pos + e->next_offset;
@@ -724,6 +714,7 @@ translate_table(struct net *net, struct xt_table_info *newinfo, void *entry0, 
		const struct ip6t_replace *repl)

{

	struct ip6t_entry *iter;

	unsigned int *offsets;

	unsigned int i;

	int ret = 0;
@@ -736,6 +727,9 @@ translate_table(struct net *net, struct xt_table_info *newinfo, void *entry0, 
		newinfo->underflow[i] = 0xFFFFFFFF;

	}



	offsets = xt_alloc_entry_offsets(newinfo->number);

	if (!offsets)

		return -ENOMEM;

	i = 0;

	/* Walk through entries, checking offsets. */

	xt_entry_foreach(iter, entry0, newinfo->size) {
@@ -745,15 +739,18 @@ translate_table(struct net *net, struct xt_table_info *newinfo, void *entry0, 
						 repl->underflow,

						 repl->valid_hooks);

		if (ret != 0)

			return ret;

			goto out_free;

		if (i < repl->num_entries)

			offsets[i] = (void *)iter - entry0;

		++i;

		if (strcmp(ip6t_get_target(iter)->u.user.name,

		    XT_ERROR_TARGET) == 0)

			++newinfo->stacksize;

	}



	ret = -EINVAL;

	if (i != repl->num_entries)

		return -EINVAL;

		goto out_free;



	/* Check hooks all assigned */

	for (i = 0; i < NF_INET_NUMHOOKS; i++) {
@@ -761,13 +758,16 @@ translate_table(struct net *net, struct xt_table_info *newinfo, void *entry0, 
		if (!(repl->valid_hooks & (1 << i)))

			continue;

		if (newinfo->hook_entry[i] == 0xFFFFFFFF)

			return -EINVAL;

			goto out_free;

		if (newinfo->underflow[i] == 0xFFFFFFFF)

			return -EINVAL;

			goto out_free;

	}



	if (!mark_source_chains(newinfo, repl->valid_hooks, entry0))

		return -ELOOP;

	if (!mark_source_chains(newinfo, repl->valid_hooks, entry0, offsets)) {

		ret = -ELOOP;

		goto out_free;

	}

	kvfree(offsets);



	/* Finally, each sanity check must pass */

	i = 0;
@@ -787,6 +787,9 @@ translate_table(struct net *net, struct xt_table_info *newinfo, void *entry0, 
		return ret;

	}



	return ret;

 out_free:

	kvfree(offsets);

	return ret;

}

net/netfilter/x_tables.c

+50 −0
Original line number Diff line number Diff line
@@ -702,6 +702,56 @@ int xt_check_entry_offsets(const void *base, 
}

EXPORT_SYMBOL(xt_check_entry_offsets);



/**

 * xt_alloc_entry_offsets - allocate array to store rule head offsets

 *

 * @size: number of entries

 *

 * Return: NULL or kmalloc'd or vmalloc'd array

 */

unsigned int *xt_alloc_entry_offsets(unsigned int size)

{

	unsigned int *off;



	off = kcalloc(size, sizeof(unsigned int), GFP_KERNEL | __GFP_NOWARN);



	if (off)

		return off;



	if (size < (SIZE_MAX / sizeof(unsigned int)))

		off = vmalloc(size * sizeof(unsigned int));



	return off;

}

EXPORT_SYMBOL(xt_alloc_entry_offsets);



/**

 * xt_find_jump_offset - check if target is a valid jump offset

 *

 * @offsets: array containing all valid rule start offsets of a rule blob

 * @target: the jump target to search for

 * @size: entries in @offset

 */

bool xt_find_jump_offset(const unsigned int *offsets,

			 unsigned int target, unsigned int size)

{

	int m, low = 0, hi = size;



	while (hi > low) {

		m = (low + hi) / 2u;



		if (offsets[m] > target)

			hi = m;

		else if (offsets[m] < target)

			low = m + 1;

		else

			return true;

	}



	return false;

}

EXPORT_SYMBOL(xt_find_jump_offset);



int xt_check_target(struct xt_tgchk_param *par,

		    unsigned int size, u_int8_t proto, bool inv_proto)

{