mac80211: fix queue selection for data frames on monitor interfaces

When ieee80211_monitor_select_queue encounters data frames, it selects
the WMM AC based on skb->priority and assumes that skb->priority
contains a valid 802.1d tag. However this assumption is incorrect, since
ieee80211_select_queue has not been called at this point.
If skb->priority > 7, an array overrun occurs, which could lead to
invalid values, resulting in crashes in the tx path.
Fix this by setting skb->priority based on the 802.11 header for QoS
frames and using the default AC for all non-QoS frames.

Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 5 insertions, 2 deletions

diff --git a/net/mac80211/iface.c b/net/mac80211/iface.c
index d62ec0803bec..32abae3ce32a 100644
--- a/net/mac80211/iface.c
+++ b/net/mac80211/iface.c
@@ -670,6 +670,7 @@ static u16 ieee80211_monitor_select_queue(struct net_device *dev,
         struct ieee80211_local *local = sdata->local;
         struct ieee80211_hdr *hdr;
         struct ieee80211_radiotap_header *rtap = (void *)skb->data;
+        u8 *p;
 
         if (local->hw.queues < 4)
                 return 0;
@@ -680,12 +681,14 @@ static u16 ieee80211_monitor_select_queue(struct net_device *dev,
 
         hdr = (void *)((u8 *)skb->data + le16_to_cpu(rtap->it_len));
 
-        if (!ieee80211_is_data(hdr->frame_control)) {
+        if (!ieee80211_is_data_qos(hdr->frame_control)) {
                 skb->priority = 7;
                 return ieee802_1d_to_ac[skb->priority];
         }
 
-        skb->priority = 0;
+        p = ieee80211_get_qos_ctl(hdr);
+        skb->priority = *p & IEEE80211_QOS_CTL_TAG1D_MASK;
+
         return ieee80211_downgrade_queue(local, skb);
 }