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 e50b707..7f3cf5f 100644
--- a/net/ipv4/netfilter/arp_tables.c
+++ b/net/ipv4/netfilter/arp_tables.c
@@ -367,6 +367,18 @@
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 @@
/* 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 2035c1f..fa7c6d0 100644
--- a/net/ipv4/netfilter/ip_tables.c
+++ b/net/ipv4/netfilter/ip_tables.c
@@ -443,6 +443,18 @@
#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 @@
/* 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 2f03d21..ea30f5f 100644
--- a/net/ipv6/netfilter/ip6_tables.c
+++ b/net/ipv6/netfilter/ip6_tables.c
@@ -455,6 +455,18 @@
#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 @@
/* 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;
