netfilter: x_tables: add compat version of xt_check_entry_offsets
32bit rulesets have different layout and alignment requirements, so once
more integrity checks get added to xt_check_entry_offsets it will reject
well-formed 32bit rulesets.
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
diff --git a/net/netfilter/x_tables.c b/net/netfilter/x_tables.c
index ec1b718..fa206ce 100644
--- a/net/netfilter/x_tables.c
+++ b/net/netfilter/x_tables.c
@@ -539,6 +539,27 @@
return 0;
}
EXPORT_SYMBOL_GPL(xt_compat_match_to_user);
+
+int xt_compat_check_entry_offsets(const void *base,
+ unsigned int target_offset,
+ unsigned int next_offset)
+{
+ const struct compat_xt_entry_target *t;
+ const char *e = base;
+
+ if (target_offset + sizeof(*t) > next_offset)
+ return -EINVAL;
+
+ t = (void *)(e + target_offset);
+ if (t->u.target_size < sizeof(*t))
+ return -EINVAL;
+
+ if (target_offset + t->u.target_size > next_offset)
+ return -EINVAL;
+
+ return 0;
+}
+EXPORT_SYMBOL(xt_compat_check_entry_offsets);
#endif /* CONFIG_COMPAT */
/**
@@ -549,6 +570,7 @@
* @next_offset: the arp/ip/ip6_t->next_offset
*
* validates that target_offset and next_offset are sane.
+ * Also see xt_compat_check_entry_offsets for CONFIG_COMPAT version.
*
* The arp/ip/ip6t_entry structure @base must have passed following tests:
* - it must point to a valid memory location
