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authorFlorian Westphal <fw@strlen.de>2016-04-01 15:17:22 +0300
committerPablo Neira Ayuso <pablo@netfilter.org>2016-04-14 01:30:35 +0300
commit36472341017529e2b12573093cc0f68719300997 (patch)
tree96f6dd9fbfcddc5e3a934d4dd812d640574897d0 /net/ipv6/netfilter
parentf24e230d257af1ad7476c6e81a8dc3127a74204e (diff)
downloadlinux-36472341017529e2b12573093cc0f68719300997.tar.xz
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>
Diffstat (limited to 'net/ipv6/netfilter')
-rw-r--r--net/ipv6/netfilter/ip6_tables.c16
1 files changed, 16 insertions, 0 deletions
diff --git a/net/ipv6/netfilter/ip6_tables.c b/net/ipv6/netfilter/ip6_tables.c
index 7b3335bce3fd..126f2a0f006a 100644
--- 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;