cfg80211: fix wext iw_freq parsing

The function to parse a struct iw_freq has a stupid bug,
it returns NULL when the channel cannot be found at all,
but NULL is supposed to mean "auto". Fix this by checking
the return value of ieee80211_get_channel() and returning
ERR_PTR(-EINVAL) if it returned NULL (channel not found).

This fixes an issue where you could say (in IBSS mode)
	iwconfig wlan0 channel 21
and it would use channel 1 instead because that's the
first available channel with IBSS allowed (which is what
the "auto" setting uses).

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

1 files changed, 18 insertions, 6 deletions

diff --git a/net/wireless/wext-compat.c b/net/wireless/wext-compat.c
index 5ef82f2ca88f..abf6b0a047d8 100644
--- a/net/wireless/wext-compat.c
+++ b/net/wireless/wext-compat.c
@@ -296,22 +296,34 @@ EXPORT_SYMBOL_GPL(cfg80211_wext_siwmlme);
 struct ieee80211_channel *cfg80211_wext_freq(struct wiphy *wiphy,
                                              struct iw_freq *freq)
 {
+        struct ieee80211_channel *chan;
+        int f;
+
+        /*
+         * Parse frequency - return NULL for auto and
+         * -EINVAL for impossible things.
+         */
         if (freq->e == 0) {
                 if (freq->m < 0)
                         return NULL;
-                else
-                        return ieee80211_get_channel(wiphy,
-                                ieee80211_channel_to_frequency(freq->m));
+                f = ieee80211_channel_to_frequency(freq->m);
         } else {
                 int i, div = 1000000;
                 for (i = 0; i < freq->e; i++)
                         div /= 10;
-                if (div > 0)
-                        return ieee80211_get_channel(wiphy, freq->m / div);
-                else
+                if (div <= 0)
                         return ERR_PTR(-EINVAL);
+                f = freq->m / div;
         }
 
+        /*
+         * Look up channel struct and return -EINVAL when
+         * it cannot be found.
+         */
+        chan = ieee80211_get_channel(wiphy, f);
+        if (!chan)
+                return ERR_PTR(-EINVAL);
+        return chan;
 }
 EXPORT_SYMBOL_GPL(cfg80211_wext_freq);