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    Subject[PATCH 3.16 289/305] netfilter: x_tables: validate targets of jumps
    3.16.37-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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