netlink: Fix spectre v1 gadget in netlink_create()

'protocol' is a user-controlled value, so sanitize it after the bounds
check to avoid using it for speculative out-of-bounds access to arrays
indexed by it.

This addresses the following accesses detected with the help of smatch:

* net/netlink/af_netlink.c:654 __netlink_create() warn: potential
  spectre issue 'nlk_cb_mutex_keys' [w]

* net/netlink/af_netlink.c:654 __netlink_create() warn: potential
  spectre issue 'nlk_cb_mutex_key_strings' [w]

* net/netlink/af_netlink.c:685 netlink_create() warn: potential spectre
  issue 'nl_table' [w] (local cap)

Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Jeremy Cline <jcline@redhat.com>
Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Jeremy Cline 2018-07-31 21:13:16 +00:00 committed by David S. Miller
parent e02ee9819a
commit bc5b6c0b62

View File

@ -63,6 +63,7 @@
#include <linux/hash.h>
#include <linux/genetlink.h>
#include <linux/net_namespace.h>
#include <linux/nospec.h>
#include <net/net_namespace.h>
#include <net/netns/generic.h>
@ -679,6 +680,7 @@ static int netlink_create(struct net *net, struct socket *sock, int protocol,
if (protocol < 0 || protocol >= MAX_LINKS)
return -EPROTONOSUPPORT;
protocol = array_index_nospec(protocol, MAX_LINKS);
netlink_lock_table();
#ifdef CONFIG_MODULES