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Subject[PATCH 3.16 083/346] netfilter: x_tables: validate targets of jumps
3.16.39-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Florian Westphal <fw@strlen.de>

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>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
net/ipv4/netfilter/arp_tables.c | 16 ++++++++++++++++
net/ipv4/netfilter/ip_tables.c | 16 ++++++++++++++++
net/ipv6/netfilter/ip6_tables.c | 16 ++++++++++++++++
3 files changed, 48 insertions(+)

--- a/net/ipv4/netfilter/arp_tables.c
+++ b/net/ipv4/netfilter/arp_tables.c
@@ -363,6 +363,19 @@ static inline bool unconditional(const s
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 stru
/* 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;
--- 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
/* 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;
--- 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
/* 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;
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