wifi: mt76: mt7996: fix crash on some tx status reports

When a wcid can't be found, link_sta can be stale from a previous batch.
The code currently assumes that if link_sta is set, wcid is also non-zero.
Fix wcid NULL pointer dereference by resetting link_sta when a wcid entry
can't be found.

Fixes: 62da647a2b20 ("wifi: mt76: mt7996: Add MLO support to mt7996_tx_check_aggr()")
Link: https://patch.msgid.link/20250827085352.51636-1-nbd@nbd.name
Signed-off-by: Felix Fietkau <nbd@nbd.name>

diff --git a/drivers/net/wireless/mediatek/mt76/mt7996/mac.c b/drivers/net/wireless/mediatek/mt76/mt7996/mac.c
index d6531b74be1f15467c06e385d0efabad806db6b8..837deb41ae13115fbe4c8c8ff881a4b98c294092 100644 (file)
--- a/drivers/net/wireless/mediatek/mt76/mt7996/mac.c
+++ b/drivers/net/wireless/mediatek/mt76/mt7996/mac.c
@@ -1247,8 +1247,10 @@ mt7996_mac_tx_free(struct mt7996_dev *dev, void *data, int len)
                        idx = FIELD_GET(MT_TXFREE_INFO_WLAN_ID, info);
                        wcid = mt76_wcid_ptr(dev, idx);
                        sta = wcid_to_sta(wcid);
-                       if (!sta)
+                       if (!sta) {
+                               link_sta = NULL;
                                goto next;
+                       }
 
                        link_sta = rcu_dereference(sta->link[wcid->link_id]);
                        if (!link_sta)