From 69d464d5938ca0f4fb3447b3e32872e0ca79efc1 Mon Sep 17 00:00:00 2001 From: Johannes Berg Date: Mon, 28 Jan 2008 17:08:56 +0100 Subject: [PATCH] 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 Signed-off-by: John W. Linville --- net/mac80211/ieee80211_sta.c | 24 ++++++++++++++++++------ 1 file changed, 18 insertions(+), 6 deletions(-) diff --git a/net/mac80211/ieee80211_sta.c b/net/mac80211/ieee80211_sta.c index 2628222a508..0d5e3fee8e5 100644 --- a/net/mac80211/ieee80211_sta.c +++ b/net/mac80211/ieee80211_sta.c @@ -3412,22 +3412,28 @@ void ieee80211_sta_scan_work(struct work_struct *work) 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 @@ void ieee80211_sta_scan_work(struct work_struct *work) } } + /* 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; } -- 2.41.1