netfilter: x_tables: speed up jump target validation

[ Upstream commit f4dc77713f8016d2e8a3295e1c9c53a21f296def ]

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 36472341017529e (~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: 36472341017529e ("netfilter: x_tables: validate targets of jumps")
Reported-by: Jeff Wu <wujiafu@gmail.com>
Tested-by: Jeff Wu <wujiafu@gmail.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>

2 files changed, 48 insertions, 44 deletions

diff --git a/net/ipv4/netfilter/arp_tables.c b/net/ipv4/netfilter/arp_tables.c
index 2953ee9e5fa0..ebf5821caefb 100644
--- a/net/ipv4/netfilter/arp_tables.c
+++ b/net/ipv4/netfilter/arp_tables.c
@@ -362,23 +362,12 @@ 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;
 
@@ -467,10 +456,11 @@ static int mark_source_chains(const struct xt_table_info *newinfo,
 					/* This a jump; chase it. */
 					duprintf("Jump rule %u -> %u\n",
 						 pos, newpos);
+					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;
@@ -630,6 +620,7 @@ 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;
 
@@ -643,6 +634,9 @@ static int translate_table(struct xt_table_info *newinfo, void *entry0,
 	}
 
 	duprintf("translate_table: size %u\n", newinfo->size);
+	offsets = xt_alloc_entry_offsets(newinfo->number);
+	if (!offsets)
+		return -ENOMEM;
 	i = 0;
 
 	/* Walk through entries, checking offsets. */
@@ -653,20 +647,21 @@ 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;
 	}
 	duprintf("translate_table: ARPT_ENTRY_ITERATE gives %d\n", ret);
-	if (ret != 0)
-		return ret;
 
+	ret = -EINVAL;
 	if (i != repl->num_entries) {
 		duprintf("translate_table: %u not %u entries\n",
 			 i, repl->num_entries);
-		return -EINVAL;
+		goto out_free;
 	}
 
 	/* Check hooks all assigned */
@@ -677,17 +672,20 @@ static int translate_table(struct xt_table_info *newinfo, void *entry0,
 		if (newinfo->hook_entry[i] == 0xFFFFFFFF) {
 			duprintf("Invalid hook entry %u %u\n",
 				 i, repl->hook_entry[i]);
-			return -EINVAL;
+			goto out_free;
 		}
 		if (newinfo->underflow[i] == 0xFFFFFFFF) {
 			duprintf("Invalid underflow %u %u\n",
 				 i, repl->underflow[i]);
-			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;
@@ -714,6 +712,9 @@ static int translate_table(struct xt_table_info *newinfo, void *entry0,
 	}
 
 	return ret;
+ out_free:
+	kvfree(offsets);
+	return ret;
 }
 
 static void get_counters(const struct xt_table_info *t,
diff --git a/net/ipv4/netfilter/ip_tables.c b/net/ipv4/netfilter/ip_tables.c
index 3bcf28bf1525..8e729cba1e59 100644
--- a/net/ipv4/netfilter/ip_tables.c
+++ b/net/ipv4/netfilter/ip_tables.c
@@ -438,23 +438,12 @@ ipt_do_table(struct sk_buff *skb,
 #endif
 }
 
-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;
 
@@ -547,10 +536,11 @@ mark_source_chains(const struct xt_table_info *newinfo,
 					/* This a jump; chase it. */
 					duprintf("Jump rule %u -> %u\n",
 						 pos, newpos);
+					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;
@@ -797,6 +787,7 @@ 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;
 
@@ -810,6 +801,9 @@ translate_table(struct net *net, struct xt_table_info *newinfo, void *entry0,
 	}
 
 	duprintf("translate_table: size %u\n", newinfo->size);
+	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) {
@@ -819,17 +813,20 @@ 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) {
 		duprintf("translate_table: %u not %u entries\n",
 			 i, repl->num_entries);
-		return -EINVAL;
+		goto out_free;
 	}
 
 	/* Check hooks all assigned */
@@ -840,17 +837,20 @@ translate_table(struct net *net, struct xt_table_info *newinfo, void *entry0,
 		if (newinfo->hook_entry[i] == 0xFFFFFFFF) {
 			duprintf("Invalid hook entry %u %u\n",
 				 i, repl->hook_entry[i]);
-			return -EINVAL;
+			goto out_free;
 		}
 		if (newinfo->underflow[i] == 0xFFFFFFFF) {
 			duprintf("Invalid underflow %u %u\n",
 				 i, repl->underflow[i]);
-			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;
@@ -877,6 +877,9 @@ translate_table(struct net *net, struct xt_table_info *newinfo, void *entry0,
 	}
 
 	return ret;
+ out_free:
+	kvfree(offsets);
+	return ret;
 }
 
 static void