[PATCH 4.14 05/23] netlink: Fix spectre v1 gadget in netlink_create()

From: Greg Kroah-Hartman
Date: Sat Aug 04 2018 - 05:04:44 EST

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


From: Jeremy Cline <jcline@xxxxxxxxxx>

[ Upstream commit bc5b6c0b62b932626a135f516a41838c510c6eba ]

'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@xxxxxxxxxx>
Signed-off-by: Jeremy Cline <jcline@xxxxxxxxxx>
Reviewed-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
net/netlink/af_netlink.c | 2 ++
1 file changed, 2 insertions(+)

--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -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/sock.h>
@@ -647,6 +648,7 @@ static int netlink_create(struct net *ne

if (protocol < 0 || protocol >= MAX_LINKS)
+ protocol = array_index_nospec(protocol, MAX_LINKS);