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Date: Thu, 18 Jan 2018 16:02:41 -0800
From: Dan Williams <dan.j.williams@...el.com>
To: linux-kernel@...r.kernel.org
Cc: linux-arch@...r.kernel.org, akpm@...ux-foundation.org,
kernel-hardening@...ts.openwall.com, gregkh@...uxfoundation.org,
Christian Lamparter <chunkeey@...il.com>, linux-wireless@...r.kernel.org,
tglx@...utronix.de, Johannes Berg <johannes@...solutions.net>,
torvalds@...ux-foundation.org, "David S. Miller" <davem@...emloft.net>,
Elena Reshetova <elena.reshetova@...el.com>, alan@...ux.intel.com
Subject: [PATCH v4 10/10] 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_idx',
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>
Cc: Johannes Berg <johannes@...solutions.net>
Cc: "David S. Miller" <davem@...emloft.net>
Cc: linux-wireless@...r.kernel.org
Signed-off-by: Dan Williams <dan.j.williams@...el.com>
---
include/linux/nospec.h | 21 +++++++++++++++++++++
net/wireless/nl80211.c | 10 +++++++---
2 files changed, 28 insertions(+), 3 deletions(-)
diff --git a/include/linux/nospec.h b/include/linux/nospec.h
index f841c11f3f1f..8af35be1869e 100644
--- a/include/linux/nospec.h
+++ b/include/linux/nospec.h
@@ -41,4 +41,25 @@ static inline unsigned long array_ptr_mask(unsigned long idx, unsigned long sz)
__u._bit &= _mask; \
__u._ptr; \
})
+
+/**
+ * array_idx - Generate a pointer to an array index, ensuring the
+ * pointer is bounded under speculation to NULL.
+ *
+ * @idx: the index of the element, must be less than LONG_MAX
+ * @sz: the number of elements in the array, must be less than LONG_MAX
+ *
+ * If @idx falls in the interval [0, @sz), returns &@idx otherwise
+ * returns NULL.
+ */
+#define array_idx(idx, sz) \
+({ \
+ union { typeof((idx)) *_ptr; unsigned long _bit; } __u; \
+ typeof(idx) *_i = &(idx); \
+ unsigned long _mask = array_ptr_mask(*_i, (sz)); \
+ \
+ __u._ptr = _i; \
+ __u._bit &= _mask; \
+ __u._ptr; \
+})
#endif /* __NOSPEC_H__ */
diff --git a/net/wireless/nl80211.c b/net/wireless/nl80211.c
index 2b3dbcd40e46..202cb1dc03ee 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 +2057,23 @@ 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, *idx;
+
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)
+ idx = array_idx(ac, NL80211_NUM_ACS);
+ if (!idx)
return -EINVAL;
-
+ txq_params->ac = *idx;
return 0;
}
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