netfilter: x_tables: don't move to non-existent next rule

commit f24e230d257af1ad7476c6e81a8dc3127a74204e upstream.

Ben Hawkes says:

 In the mark_source_chains function (net/ipv4/netfilter/ip_tables.c) it
 is possible for a user-supplied ipt_entry structure to have a large
 next_offset field. This field is not bounds checked prior to writing a
 counter value at the supplied offset.

Base chains enforce absolute verdict.

User defined chains are supposed to end with an unconditional return,
xtables userspace adds them automatically.

But if such return is missing we will move to non-existent next rule.

Reported-by: Ben Hawkes <hawkes@google.com>
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 36a30fab8625c6d2e1f01d0a2aedd55a552499f6..e50b707c39c044970b3a9d7281257a7f4b43afe8 100644 (file)
--- a/net/ipv4/netfilter/arp_tables.c
+++ b/net/ipv4/netfilter/arp_tables.c
@@ -439,6 +439,8 @@ static int mark_source_chains(const struct xt_table_info *newinfo,
                                size = e->next_offset;
                                e = (struct arpt_entry *)
                                        (entry0 + pos + size);
+                               if (pos + size >= newinfo->size)
+                                       return 0;
                                e->counters.pcnt = pos;
                                pos += size;
                        } else {
@@ -461,6 +463,8 @@ static int mark_source_chains(const struct xt_table_info *newinfo,
                                } else {
                                        /* ... this is a fallthru */
                                        newpos = pos + e->next_offset;
+                                       if (newpos >= newinfo->size)
+                                               return 0;
                                }
                                e = (struct arpt_entry *)
                                        (entry0 + newpos);
@@ -691,10 +695,8 @@ static int translate_table(struct xt_table_info *newinfo, void *entry0,
                }
        }
 
-       if (!mark_source_chains(newinfo, repl->valid_hooks, entry0)) {
-               duprintf("Looping hook\n");
+       if (!mark_source_chains(newinfo, repl->valid_hooks, entry0))
                return -ELOOP;
-       }
 
        /* Finally, each sanity check must pass */
        i = 0;

diff --git a/net/ipv4/netfilter/ip_tables.c b/net/ipv4/netfilter/ip_tables.c
index 99d46b0a4eade0bcb958e9a5b10607b637f8ed48..2035c1f4cc260d8fd013c56475c2b1a64128dc95 100644 (file)
--- a/net/ipv4/netfilter/ip_tables.c
+++ b/net/ipv4/netfilter/ip_tables.c
@@ -520,6 +520,8 @@ mark_source_chains(const struct xt_table_info *newinfo,
                                size = e->next_offset;
                                e = (struct ipt_entry *)
                                        (entry0 + pos + size);
+                               if (pos + size >= newinfo->size)
+                                       return 0;
                                e->counters.pcnt = pos;
                                pos += size;
                        } else {
@@ -541,6 +543,8 @@ mark_source_chains(const struct xt_table_info *newinfo,
                                } else {
                                        /* ... this is a fallthru */
                                        newpos = pos + e->next_offset;
+                                       if (newpos >= newinfo->size)
+                                               return 0;
                                }
                                e = (struct ipt_entry *)
                                        (entry0 + newpos);

diff --git a/net/ipv6/netfilter/ip6_tables.c b/net/ipv6/netfilter/ip6_tables.c
index 6198807e06f4b342dd15c2014facb9c03f7b2399..2f03d2141ae783fc6f596343611cca1e6ad2cacc 100644 (file)
--- a/net/ipv6/netfilter/ip6_tables.c
+++ b/net/ipv6/netfilter/ip6_tables.c
@@ -532,6 +532,8 @@ mark_source_chains(const struct xt_table_info *newinfo,
                                size = e->next_offset;
                                e = (struct ip6t_entry *)
                                        (entry0 + pos + size);
+                               if (pos + size >= newinfo->size)
+                                       return 0;
                                e->counters.pcnt = pos;
                                pos += size;
                        } else {
@@ -553,6 +555,8 @@ mark_source_chains(const struct xt_table_info *newinfo,
                                } else {
                                        /* ... this is a fallthru */
                                        newpos = pos + e->next_offset;
+                                       if (newpos >= newinfo->size)
+                                               return 0;
                                }
                                e = (struct ip6t_entry *)
                                        (entry0 + newpos);