[PATCH] mac80211_hwsim: Fix possible Spectre-v1 for hwsim_world_regdom_custom

From: Jinbum Park
Date: Tue Jul 31 2018 - 10:10:49 EST


User controls @idx which to be used as index of hwsim_world_regdom_custom.
So, It can be exploited via Spectre-like attack. (speculative execution)

This kind of attack leaks address of hwsim_world_regdom_custom,
It leads an attacker to bypass security mechanism such as KASLR.

So sanitize @idx before using it to prevent attack.

I leveraged strategy [1] to find and exploit this gadget.

[1] https://github.com/jinb-park/linux-exploit/
tree/master/exploit-remaining-spectre-gadget/

Signed-off-by: Jinbum Park <jinb.park7@xxxxxxxxx>
---
drivers/net/wireless/mac80211_hwsim.c | 4 ++++
1 file changed, 4 insertions(+)

diff --git a/drivers/net/wireless/mac80211_hwsim.c b/drivers/net/wireless/mac80211_hwsim.c
index 998dfac..b41fdc3 100644
--- a/drivers/net/wireless/mac80211_hwsim.c
+++ b/drivers/net/wireless/mac80211_hwsim.c
@@ -34,6 +34,7 @@
#include <net/net_namespace.h>
#include <net/netns/generic.h>
#include <linux/rhashtable.h>
+#include <linux/nospec.h>
#include "mac80211_hwsim.h"

#define WARN_QUEUE 100
@@ -3350,6 +3351,9 @@ static int hwsim_new_radio_nl(struct sk_buff *msg, struct genl_info *info)
kfree(hwname);
return -EINVAL;
}
+
+ idx = array_index_nospec(idx,
+ ARRAY_SIZE(hwsim_world_regdom_custom));
param.regd = hwsim_world_regdom_custom[idx];
}

--
1.9.1