[PATCH 4.16 22/26] netfilter: x_tables: limit allocation requests for blob rule heads

[Greg Kroah-Hartman]

4.16-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Florian Westphal <f...@strlen.de>

commit 9d5c12a7c08f67999772065afd50fb222072114e upstream.

This is a very conservative limit (134217728 rules), but good
enough to not trigger frequent oom from syzkaller.

Signed-off-by: Florian Westphal <f...@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pa...@netfilter.org>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>

---
 net/netfilter/x_tables.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/net/netfilter/x_tables.c
+++ b/net/netfilter/x_tables.c
@@ -818,6 +818,9 @@ EXPORT_SYMBOL(xt_check_entry_offsets);
  */
 unsigned int *xt_alloc_entry_offsets(unsigned int size)
 {
+       if (size > XT_MAX_TABLE_SIZE / sizeof(unsigned int))
+               return NULL;
+
        return kvmalloc_array(size, sizeof(unsigned int), GFP_KERNEL | 
__GFP_ZERO);
 
 }