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Commit 83f5e2cf authored by Johannes Berg's avatar Johannes Berg Committed by John W. Linville
Browse files

cfg80211: prohibit scanning the same channel more than once 



It isn't very useful to scan the same channel more than once
during a given scan, and some hardware (notably iwlwifi) can
only scan a limited number of channels at a time. To prevent
any overflows, simply disallow scanning any channel multiple
times in a given scan command. This is a small change in the
userspace ABI, but the only user, wpa_supplicant, never asks
for a scan with the same frequency listed twice.

Signed-off-by: default avatarJohannes Berg <johannes@sipsolutions.net>
Signed-off-by: default avatarJohn W. Linville <linville@tuxdriver.com>
parent 386aa23d

net/wireless/nl80211.c

+30 −3
Original line number Diff line number Diff line
@@ -2695,6 +2695,31 @@ static int nl80211_set_reg(struct sk_buff *skb, struct genl_info *info) 
	return r;

}



static int validate_scan_freqs(struct nlattr *freqs)

{

	struct nlattr *attr1, *attr2;

	int n_channels = 0, tmp1, tmp2;



	nla_for_each_nested(attr1, freqs, tmp1) {

		n_channels++;

		/*

		 * Some hardware has a limited channel list for

		 * scanning, and it is pretty much nonsensical

		 * to scan for a channel twice, so disallow that

		 * and don't require drivers to check that the

		 * channel list they get isn't longer than what

		 * they can scan, as long as they can scan all

		 * the channels they registered at once.

		 */

		nla_for_each_nested(attr2, freqs, tmp2)

			if (attr1 != attr2 &&

			    nla_get_u32(attr1) == nla_get_u32(attr2))

				return 0;

	}



	return n_channels;

}



static int nl80211_trigger_scan(struct sk_buff *skb, struct genl_info *info)

{

	struct cfg80211_registered_device *drv;
@@ -2704,7 +2729,7 @@ static int nl80211_trigger_scan(struct sk_buff *skb, struct genl_info *info) 
	struct ieee80211_channel *channel;

	struct nlattr *attr;

	struct wiphy *wiphy;

	int err, tmp, n_ssids = 0, n_channels = 0, i;

	int err, tmp, n_ssids = 0, n_channels, i;

	enum ieee80211_band band;

	size_t ie_len;
@@ -2735,13 +2760,15 @@ static int nl80211_trigger_scan(struct sk_buff *skb, struct genl_info *info) 
	}



	if (info->attrs[NL80211_ATTR_SCAN_FREQUENCIES]) {

		nla_for_each_nested(attr, info->attrs[NL80211_ATTR_SCAN_FREQUENCIES], tmp)

			n_channels++;

		n_channels = validate_scan_freqs(

				info->attrs[NL80211_ATTR_SCAN_FREQUENCIES]);

		if (!n_channels) {

			err = -EINVAL;

			goto out;

		}

	} else {

		n_channels = 0;



		for (band = 0; band < IEEE80211_NUM_BANDS; band++)

			if (wiphy->bands[band])

				n_channels += wiphy->bands[band]->n_channels;