netfilter: x_tables: limit allocation requests for blob rule heads

BugLink: http://bugs.launchpad.net/bugs/1774063
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 <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

diff --git a/net/netfilter/x_tables.c b/net/netfilter/x_tables.c
index 7ca4586d1bda3ea44ab06b996c69aac5191417b7..fcad68ffdbd4f2fc452bc2f09277b29c74aba875 100644 (file)
--- a/net/netfilter/x_tables.c
+++ b/net/netfilter/x_tables.c
@@ -819,6 +819,9 @@ 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);
 
 }