netfilter: x_tables: validate targets of jumps

commit 36472341017529e2b12573093cc0f68719300997 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/net/ipv4/netfilter/arp_tables.c b/net/ipv4/netfilter/arp_tables.c
index 993da4aa73a35ee36f4d20b23d65075cbec2273b..5f3e807f7227373aed027a2e9e6b3afa14c298ce 100644 (file)
--- a/net/ipv4/netfilter/arp_tables.c
+++ b/net/ipv4/netfilter/arp_tables.c
@@ -363,6 +363,19 @@ 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 void *entry0,
+                            const struct arpt_entry *target)
+{
+       struct arpt_entry *iter;
+
+       xt_entry_foreach(iter, entry0, 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.
  */
@@ -456,6 +469,10 @@ 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, entry0, 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 b75c5bbca32f2c7a10fab3ca493cd55ddff87ac2..f402317b5432ea5f98c94806874c1a8fb777072e 100644 (file)
--- a/net/ipv4/netfilter/ip_tables.c
+++ b/net/ipv4/netfilter/ip_tables.c
@@ -439,6 +439,19 @@ ipt_do_table(struct sk_buff *skb,
 #endif
 }
 
+static bool find_jump_target(const struct xt_table_info *t,
+                            const void *entry0,
+                            const struct ipt_entry *target)
+{
+       struct ipt_entry *iter;
+
+       xt_entry_foreach(iter, entry0, 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
@@ -536,6 +549,10 @@ 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, entry0, 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 9367bbdf72630253cf5721ecf35d986d5891a935..e31263985fe1e798ee6ba187d94bc1b5405a5d5b 100644 (file)
--- a/net/ipv6/netfilter/ip6_tables.c
+++ b/net/ipv6/netfilter/ip6_tables.c
@@ -449,6 +449,19 @@ ip6t_do_table(struct sk_buff *skb,
 #endif
 }
 
+static bool find_jump_target(const struct xt_table_info *t,
+                            const void *entry0,
+                            const struct ip6t_entry *target)
+{
+       struct ip6t_entry *iter;
+
+       xt_entry_foreach(iter, entry0, 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
@@ -546,6 +559,10 @@ 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, entry0, e))
+                                               return 0;
                                } else {
                                        /* ... this is a fallthru */
                                        newpos = pos + e->next_offset;