nl80211: Sanitize array index in parse_txq_params

Wireless drivers rely on parse_txq_params to validate that txq_params->ac
is less than NL80211_NUM_ACS by the time the low-level driver's ->conf_tx()
handler is called. Use a new helper, array_index_nospec(), to sanitize
txq_params->ac with respect to speculation. I.e. ensure that any
speculation into ->conf_tx() handlers is done with a value of
txq_params->ac that is within the bounds of [0, NL80211_NUM_ACS).

Reported-by: Christian Lamparter <chunkeey@gmail.com>
Reported-by: Elena Reshetova <elena.reshetova@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Johannes Berg <johannes@sipsolutions.net>
Cc: linux-arch@vger.kernel.org
Cc: kernel-hardening@lists.openwall.com
Cc: gregkh@linuxfoundation.org
Cc: linux-wireless@vger.kernel.org
Cc: torvalds@linux-foundation.org
Cc: "David S. Miller" <davem@davemloft.net>
Cc: alan@linux.intel.com
Link: https://lkml.kernel.org/r/151727419584.33451.7700736761686184303.stgit@dwillia2-desk3.amr.corp.intel.com

1 files changed, 6 insertions, 3 deletions

diff --git a/net/wireless/nl80211.c b/net/wireless/nl80211.c
index 542a4fc0a8d7..4bbcfc1e2d43 100644
--- a/net/wireless/nl80211.c
+++ b/net/wireless/nl80211.c
@@ -16,6 +16,7 @@
 #include <linux/nl80211.h>
 #include <linux/rtnetlink.h>
 #include <linux/netlink.h>
+#include <linux/nospec.h>
 #include <linux/etherdevice.h>
 #include <net/net_namespace.h>
 #include <net/genetlink.h>
@@ -2056,20 +2057,22 @@ static const struct nla_policy txq_params_policy[NL80211_TXQ_ATTR_MAX + 1] = {
 static int parse_txq_params(struct nlattr *tb[],
                             struct ieee80211_txq_params *txq_params)
 {
+        u8 ac;
+
         if (!tb[NL80211_TXQ_ATTR_AC] || !tb[NL80211_TXQ_ATTR_TXOP] ||
             !tb[NL80211_TXQ_ATTR_CWMIN] || !tb[NL80211_TXQ_ATTR_CWMAX] ||
             !tb[NL80211_TXQ_ATTR_AIFS])
                 return -EINVAL;
 
-        txq_params->ac = nla_get_u8(tb[NL80211_TXQ_ATTR_AC]);
+        ac = nla_get_u8(tb[NL80211_TXQ_ATTR_AC]);
         txq_params->txop = nla_get_u16(tb[NL80211_TXQ_ATTR_TXOP]);
         txq_params->cwmin = nla_get_u16(tb[NL80211_TXQ_ATTR_CWMIN]);
         txq_params->cwmax = nla_get_u16(tb[NL80211_TXQ_ATTR_CWMAX]);
         txq_params->aifs = nla_get_u8(tb[NL80211_TXQ_ATTR_AIFS]);
 
-        if (txq_params->ac >= NL80211_NUM_ACS)
+        if (ac >= NL80211_NUM_ACS)
                 return -EINVAL;
-
+        txq_params->ac = array_index_nospec(ac, NL80211_NUM_ACS);
         return 0;
 }