iwlwifi: mvm: invalidate IDs of internal stations at mvm start

Having sta_id not set for aux_sta and snif_sta can potentially lead to a
hard to debug issue in case remove station is called without an add. In
this case sta_id 0, an unrelated regular station, will be removed.

In fact, we do have a FW assert that occures rarely and from the debug
data analysis it looks like sta_id 0 is removed by mistake, though it's
hard to pinpoint the exact flow. The WARN_ON in this patch should help
to find it.
Signed-off-by: Gregory Greenman <gregory.greenman@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/iwlwifi.20210122144849.5dc6dd9b22d5.I2add1b5ad24d0d0a221de79d439c09f88fcaf15d@changeid

drivers/net/wireless/intel/iwlwifi/mvm/ops.c

@@ -791,6 +791,10 @@ iwl_op_mode_mvm_start(struct iwl_trans *trans, const struct iwl_cfg *cfg,
 	if (!mvm->scan_cmd)
 		goto out_free;
 
+	/* invalidate ids to prevent accidental removal of sta_id 0 */
+	mvm->aux_sta.sta_id = IWL_MVM_INVALID_STA;
+	mvm->snif_sta.sta_id = IWL_MVM_INVALID_STA;
+
 	/* Set EBS as successful as long as not stated otherwise by the FW. */
 	mvm->last_ebs_successful = true;
 

drivers/net/wireless/intel/iwlwifi/mvm/sta.c

@@ -2057,6 +2057,9 @@ int iwl_mvm_rm_snif_sta(struct iwl_mvm *mvm, struct ieee80211_vif *vif)
 
 	lockdep_assert_held(&mvm->mutex);
 
+	if (WARN_ON_ONCE(mvm->snif_sta.sta_id == IWL_MVM_INVALID_STA))
+		return -EINVAL;
+
 	iwl_mvm_disable_txq(mvm, NULL, mvm->snif_queue, IWL_MAX_TID_COUNT, 0);
 	ret = iwl_mvm_rm_sta_common(mvm, mvm->snif_sta.sta_id);
 	if (ret)
@@ -2071,6 +2074,9 @@ int iwl_mvm_rm_aux_sta(struct iwl_mvm *mvm)
 
 	lockdep_assert_held(&mvm->mutex);
 
+	if (WARN_ON_ONCE(mvm->aux_sta.sta_id == IWL_MVM_INVALID_STA))
+		return -EINVAL;
+
 	iwl_mvm_disable_txq(mvm, NULL, mvm->aux_queue, IWL_MAX_TID_COUNT, 0);
 	ret = iwl_mvm_rm_sta_common(mvm, mvm->aux_sta.sta_id);
 	if (ret)