linux-kernel - [PATCH 3.16 58/76] nl80211: Sanitize array index in parse_txq

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Message-ID: <lsq.1520823972.857925406@decadent.org.uk>
Date:   Mon, 12 Mar 2018 03:06:12 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, kernel-hardening@...ts.openwall.com,
        torvalds@...ux-foundation.org,
        "Elena Reshetova" <elena.reshetova@...el.com>,
        "Thomas Gleixner" <tglx@...utronix.de>, alan@...ux.intel.com,
        "Dan Williams" <dan.j.williams@...el.com>,
        "David S. Miller" <davem@...emloft.net>,
        linux-arch@...r.kernel.org,
        "Christian Lamparter" <chunkeey@...il.com>,
        linux-wireless@...r.kernel.org, gregkh@...uxfoundation.org,
        "Johannes Berg" <johannes@...solutions.net>
Subject: [PATCH 3.16 58/76] nl80211: Sanitize array index in parse_txq_params

3.16.56-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Dan Williams <dan.j.williams@...el.com>

commit 259d8c1e984318497c84eef547bbb6b1d9f4eb05 upstream.

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@...il.com>
Reported-by: Elena Reshetova <elena.reshetova@...el.com>
Signed-off-by: Dan Williams <dan.j.williams@...el.com>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Acked-by: Johannes Berg <johannes@...solutions.net>
Cc: linux-arch@...r.kernel.org
Cc: kernel-hardening@...ts.openwall.com
Cc: gregkh@...uxfoundation.org
Cc: linux-wireless@...r.kernel.org
Cc: torvalds@...ux-foundation.org
Cc: "David S. Miller" <davem@...emloft.net>
Cc: alan@...ux.intel.com
Link: https://lkml.kernel.org/r/151727419584.33451.7700736761686184303.stgit@dwillia2-desk3.amr.corp.intel.com
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 net/wireless/nl80211.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

--- a/net/wireless/nl80211.c
+++ b/net/wireless/nl80211.c
@@ -14,6 +14,7 @@
 #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>
@@ -1829,20 +1830,22 @@ static const struct nla_policy txq_param
 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;
 }