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Subject[PATCH 3.12 28/88] netfilter: x_tables: validate targets of jumps
Date
From: Florian Westphal <fw@strlen.de>

3.12-stable review patch. If anyone has any objections, please let me know.

===============

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: Jiri Slaby <jslaby@suse.cz>
---
net/ipv4/netfilter/arp_tables.c | 17 +++++++++++++++++
net/ipv4/netfilter/ip_tables.c | 17 +++++++++++++++++
net/ipv6/netfilter/ip6_tables.c | 17 +++++++++++++++++
3 files changed, 51 insertions(+)

diff --git a/net/ipv4/netfilter/arp_tables.c b/net/ipv4/netfilter/arp_tables.c
index 7460b7bef3ab..473ec559ce7b 100644
--- a/net/ipv4/netfilter/arp_tables.c
+++ b/net/ipv4/netfilter/arp_tables.c
@@ -358,6 +358,19 @@ 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.
*/
@@ -451,6 +464,10 @@ 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 8fc22eed9603..dba9d8070d07 100644
--- a/net/ipv4/netfilter/ip_tables.c
+++ b/net/ipv4/netfilter/ip_tables.c
@@ -434,6 +434,19 @@ 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
@@ -531,6 +544,10 @@ 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 63f7876c4f29..97a8d2525c26 100644
--- a/net/ipv6/netfilter/ip6_tables.c
+++ b/net/ipv6/netfilter/ip6_tables.c
@@ -444,6 +444,19 @@ 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
@@ -541,6 +554,10 @@ 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;
--
2.9.1
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