mac80211: fix scan band off-by-one error
When checking for the next band to advance to, there
was an off-by-one error that could lead to an access
to an invalid array index. Additionally, the later
check for scan_band >= IEEE80211_NUM_BANDS is not
required since that will never be true.
This also improves the comments related to that code.
Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/net/mac80211/ieee80211_sta.c b/net/mac80211/ieee80211_sta.c
index 2628222..0d5e3fe 100644
--- a/net/mac80211/ieee80211_sta.c
+++ b/net/mac80211/ieee80211_sta.c
@@ -3412,22 +3412,28 @@
switch (local->scan_state) {
case SCAN_SET_CHANNEL:
- /* get current scan band */
+ /*
+ * Get current scan band. scan_band may be IEEE80211_NUM_BANDS
+ * after we successfully scanned the last channel of the last
+ * band (and the last band is supported by the hw)
+ */
if (local->scan_band < IEEE80211_NUM_BANDS)
sband = local->hw.wiphy->bands[local->scan_band];
else
sband = NULL;
- /* if we started at an unsupported one, advance */
- while (!sband && local->scan_band < IEEE80211_NUM_BANDS) {
+ /*
+ * If we are at an unsupported band and have more bands
+ * left to scan, advance to the next supported one.
+ */
+ while (!sband && local->scan_band < IEEE80211_NUM_BANDS - 1) {
local->scan_band++;
sband = local->hw.wiphy->bands[local->scan_band];
local->scan_channel_idx = 0;
}
- if (!sband ||
- (local->scan_channel_idx >= sband->n_channels &&
- local->scan_band >= IEEE80211_NUM_BANDS)) {
+ /* if no more bands/channels left, complete scan */
+ if (!sband || local->scan_channel_idx >= sband->n_channels) {
ieee80211_scan_completed(local_to_hw(local));
return;
}
@@ -3449,8 +3455,14 @@
}
}
+ /* advance state machine to next channel/band */
local->scan_channel_idx++;
if (local->scan_channel_idx >= sband->n_channels) {
+ /*
+ * scan_band may end up == IEEE80211_NUM_BANDS, but
+ * we'll catch that case above and complete the scan
+ * if that is the case.
+ */
local->scan_band++;
local->scan_channel_idx = 0;
}