mac80211: fix invalid band deref building preq IEs

The function building probe-request IEs does not validate the band is
supported before dereferencing it. This can result in a panic when
all bands are traversed, as done during sched-scan start.

Warn when this happens and return an empty probe request. Also fix
sched-scan to not waste memory on unsupported bands.

Signed-off-by: Arik Nemtsov <arik@wizery.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

2 files changed, 5 insertions, 0 deletions

diff --git a/net/mac80211/scan.c b/net/mac80211/scan.c
index 379f178eab5f..1ff04f689d1f 100644
--- a/net/mac80211/scan.c
+++ b/net/mac80211/scan.c
@@ -928,6 +928,9 @@ int ieee80211_request_sched_scan_start(struct ieee80211_sub_if_data *sdata,
         }
 
         for (i = 0; i < IEEE80211_NUM_BANDS; i++) {
+                if (!local->hw.wiphy->bands[i])
+                        continue;
+
                 local->sched_scan_ies.ie[i] = kzalloc(2 +
                                                       IEEE80211_MAX_SSID_LEN +
                                                       local->scan_ies_len +
diff --git a/net/mac80211/util.c b/net/mac80211/util.c
index 64493a7bef1a..596db0c2a113 100644
--- a/net/mac80211/util.c
+++ b/net/mac80211/util.c
@@ -999,6 +999,8 @@ int ieee80211_build_preq_ies(struct ieee80211_local *local, u8 *buffer,
         int ext_rates_len;
 
         sband = local->hw.wiphy->bands[band];
+        if (WARN_ON_ONCE(!sband))
+                return 0;
 
         pos = buffer;