cfg80211: validate remain-on-channel time better

The remain-on-channel time validation shouldn't
depend on the value of HZ, as it does now with
the check against jiffies, since then you might
use a value that works on one system but not on
another. Fix it by checking against a minimum
that's fixed.

Also add validation of the wait duration for a
management frame TX since this also translates
into remain-on-channel internally.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

include/linux/nl80211.h

@@ -1522,6 +1522,8 @@ enum nl80211_attrs {
 #define NL80211_MAX_NR_CIPHER_SUITES		5
 #define NL80211_MAX_NR_AKM_SUITES		2
 
+#define NL80211_MIN_REMAIN_ON_CHANNEL_TIME	10
+
 /**
  * enum nl80211_iftype - (virtual) interface types
  *

net/wireless/nl80211.c

@@ -5545,18 +5545,18 @@ static int nl80211_remain_on_channel(struct sk_buff *skb,
 
 	duration = nla_get_u32(info->attrs[NL80211_ATTR_DURATION]);
 
+	if (!rdev->ops->remain_on_channel ||
+	    !(rdev->wiphy.flags & WIPHY_FLAG_HAS_REMAIN_ON_CHANNEL))
+		return -EOPNOTSUPP;
+
 	/*
-	 * We should be on that channel for at least one jiffie,
-	 * and more than 5 seconds seems excessive.
+	 * We should be on that channel for at least a minimum amount of
+	 * time (10ms) but no longer than the driver supports.
 	 */
-	if (!duration || !msecs_to_jiffies(duration) ||
+	if (duration < NL80211_MIN_REMAIN_ON_CHANNEL_TIME ||
 	    duration > rdev->wiphy.max_remain_on_channel_duration)
 		return -EINVAL;
 
-	if (!rdev->ops->remain_on_channel ||
-	    !(rdev->wiphy.flags & WIPHY_FLAG_HAS_REMAIN_ON_CHANNEL))
-		return -EOPNOTSUPP;
-
 	if (info->attrs[NL80211_ATTR_WIPHY_CHANNEL_TYPE] &&
 	    !nl80211_valid_channel_type(info, &channel_type))
 		return -EINVAL;
@@ -5827,6 +5827,15 @@ static int nl80211_tx_mgmt(struct sk_buff *skb, struct genl_info *info)
 		if (!(rdev->wiphy.flags & WIPHY_FLAG_OFFCHAN_TX))
 			return -EINVAL;
 		wait = nla_get_u32(info->attrs[NL80211_ATTR_DURATION]);
+
+		/*
+		 * We should wait on the channel for at least a minimum amount
+		 * of time (10ms) but no longer than the driver supports.
+		 */
+		if (wait < NL80211_MIN_REMAIN_ON_CHANNEL_TIME ||
+		    wait > rdev->wiphy.max_remain_on_channel_duration)
+			return -EINVAL;
+
 	}
 
 	if (info->attrs[NL80211_ATTR_WIPHY_CHANNEL_TYPE]) {