netfilter: x_tables: limit allocation requests for blob rule heads

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

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 dc68ac49614a94168ab947e04d2855626afdccda..01f8e122e74ee3cd62afaa84bb6ebfe3d938d43d 100644 (file)
--- a/net/netfilter/x_tables.c
+++ b/net/netfilter/x_tables.c
@@ -894,6 +894,9 @@ 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);
 
 }