netfilter: x_tables: cap allocations at 512 mbyte

Arbitrary limit, however, this still allows huge rulesets
(> 1 million rules).  This helps with automated fuzzer as it prevents
oom-killer invocation.

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 4e6cbb3..dc68ac4 100644 (file)
--- a/net/netfilter/x_tables.c
+++ b/net/netfilter/x_tables.c
@@ -40,6 +40,7 @@ MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
 MODULE_DESCRIPTION("{ip,ip6,arp,eb}_tables backend module");
 
 #define XT_PCPU_BLOCK_SIZE 4096
+#define XT_MAX_TABLE_SIZE      (512 * 1024 * 1024)
 
 struct compat_delta {
        unsigned int offset; /* offset in kernel */
@@ -1117,7 +1118,7 @@ struct xt_table_info *xt_alloc_table_info(unsigned int size)
        struct xt_table_info *info = NULL;
        size_t sz = sizeof(*info) + size;
 
-       if (sz < sizeof(*info))
+       if (sz < sizeof(*info) || sz >= XT_MAX_TABLE_SIZE)
                return NULL;
 
        /* __GFP_NORETRY is not fully supported by kvmalloc but it should