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

[ Upstream commit f24e230d257af1ad7476c6e81a8dc3127a74204e ]

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: Sasha Levin <sasha.levin@oracle.com>

diff --git a/net/ipv4/netfilter/arp_tables.c b/net/ipv4/netfilter/arp_tables.c
index 738e62d548ce7bc18ea8ffab4fcb77eb029f05da..993da4aa73a35ee36f4d20b23d65075cbec2273b 100644 (file)
--- a/net/ipv4/netfilter/arp_tables.c
+++ b/net/ipv4/netfilter/arp_tables.c
@@ -435,6 +435,8 @@ 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 {
@@ -457,6 +459,8 @@ 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);
@@ -680,10 +684,8 @@ 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 2c8fb724dde5da41591b862ccafd110f65fc7fdd..b75c5bbca32f2c7a10fab3ca493cd55ddff87ac2 100644 (file)
--- a/net/ipv4/netfilter/ip_tables.c
+++ b/net/ipv4/netfilter/ip_tables.c
@@ -516,6 +516,8 @@ 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 {
@@ -537,6 +539,8 @@ 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 bc0615b1cf63e3046b65a800ced5c9ad2bb64dc0..9367bbdf72630253cf5721ecf35d986d5891a935 100644 (file)
--- a/net/ipv6/netfilter/ip6_tables.c
+++ b/net/ipv6/netfilter/ip6_tables.c
@@ -526,6 +526,8 @@ 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 {
@@ -547,6 +549,8 @@ 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);