netfilter: x_tables: validate targets of jumps

When we see a jump also check that the offset gets us to beginning of
a rule (an ipt_entry).

The extra overhead is negible, even with absurd cases.

300k custom rules, 300k jumps to 'next' user chain:
[ plus one jump from INPUT to first userchain ]:

Before:
real    0m24.874s
user    0m7.532s
sys     0m16.076s

After:
real    0m27.464s
user    0m7.436s
sys     0m18.840s

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

diff --git a/net/ipv4/netfilter/arp_tables.c b/net/ipv4/netfilter/arp_tables.c
index 82a434bf865366e1605f855697f17b291e585ad4..ec37f7c3a033a149f3bf9e787bb77f221ab9e20a 100644 (file)
--- a/net/ipv4/netfilter/arp_tables.c
+++ b/net/ipv4/netfilter/arp_tables.c
@@ -367,6 +367,18 @@ 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.
  */
@@ -460,6 +472,10 @@ static int mark_source_chains(const struct xt_table_info *newinfo,
                                        /* This a jump; chase it. */
                                        duprintf("Jump rule %u -> %u\n",
                                                 pos, newpos);
+                                       e = (struct arpt_entry *)
+                                               (entry0 + newpos);
+                                       if (!find_jump_target(newinfo, e))
+                                               return 0;
                                } else {
                                        /* ... this is a fallthru */
                                        newpos = pos + e->next_offset;

diff --git a/net/ipv4/netfilter/ip_tables.c b/net/ipv4/netfilter/ip_tables.c
index e301a3db4717ab8d6e161525ba8350343d64103a..503038ea7735b270f22232a013d230f98dbfe957 100644 (file)
--- a/net/ipv4/netfilter/ip_tables.c
+++ b/net/ipv4/netfilter/ip_tables.c
@@ -443,6 +443,18 @@ 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
@@ -540,6 +552,10 @@ mark_source_chains(const struct xt_table_info *newinfo,
                                        /* This a jump; chase it. */
                                        duprintf("Jump rule %u -> %u\n",
                                                 pos, newpos);
+                                       e = (struct ipt_entry *)
+                                               (entry0 + newpos);
+                                       if (!find_jump_target(newinfo, e))
+                                               return 0;
                                } else {
                                        /* ... this is a fallthru */
                                        newpos = pos + e->next_offset;

diff --git a/net/ipv6/netfilter/ip6_tables.c b/net/ipv6/netfilter/ip6_tables.c
index 7b3335bce3fda4c719625fc04e0783b0fd4448f7..126f2a0f006aa71f2135c83949a6b5e106ab5c00 100644 (file)
--- a/net/ipv6/netfilter/ip6_tables.c
+++ b/net/ipv6/netfilter/ip6_tables.c
@@ -455,6 +455,18 @@ ip6t_do_table(struct sk_buff *skb,
 #endif
 }
 
+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
@@ -552,6 +564,10 @@ mark_source_chains(const struct xt_table_info *newinfo,
                                        /* This a jump; chase it. */
                                        duprintf("Jump rule %u -> %u\n",
                                                 pos, newpos);
+                                       e = (struct ip6t_entry *)
+                                               (entry0 + newpos);
+                                       if (!find_jump_target(newinfo, e))
+                                               return 0;
                                } else {
                                        /* ... this is a fallthru */
                                        newpos = pos + e->next_offset;