qtnfmac: fix potential Spectre vulnerabilities

Fix potential Spectre vulnerabilities and other warnings
reported by smatch:

drivers/net/wireless/quantenna/qtnfmac/core.c:49 qtnf_core_get_mac() warn: potential spectre issue 'bus->mac' [r] (local cap)
drivers/net/wireless/quantenna/qtnfmac/core.c:51 qtnf_core_get_mac() warn: possible spectre second half.  'mac'
drivers/net/wireless/quantenna/qtnfmac/event.c:671 qtnf_event_parse() warn: potential spectre issue 'mac->iflist' [r] (local cap)
drivers/net/wireless/quantenna/qtnfmac/pcie/pearl_pcie.c:912 qtnf_pcie_skb_send() warn: variable dereferenced before check 'skb' (see line 881)
Signed-off-by: Sergey Matyukevich <sergey.matyukevich.os@quantenna.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>

drivers/net/wireless/quantenna/qtnfmac/core.c

@@ -4,6 +4,7 @@
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/if_ether.h>
+#include <linux/nospec.h>
 
 #include "core.h"
 #include "bus.h"
@@ -41,11 +42,12 @@ struct qtnf_wmac *qtnf_core_get_mac(const struct qtnf_bus *bus, u8 macid)
 {
 	struct qtnf_wmac *mac = NULL;
 
-	if (unlikely(macid >= QTNF_MAX_MAC)) {
+	if (macid >= QTNF_MAX_MAC) {
 		pr_err("invalid MAC index %u\n", macid);
 		return NULL;
 	}
 
+	macid = array_index_nospec(macid, QTNF_MAX_MAC);
 	mac = bus->mac[macid];
 
 	if (unlikely(!mac)) {

drivers/net/wireless/quantenna/qtnfmac/event.c

@@ -4,6 +4,7 @@
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/slab.h>
+#include <linux/nospec.h>
 
 #include "cfg80211.h"
 #include "core.h"
@@ -632,18 +633,20 @@ static int qtnf_event_parse(struct qtnf_wmac *mac,
 	int ret = -1;
 	u16 event_id;
 	u16 event_len;
+	u8 vifid;
 
 	event = (const struct qlink_event *)event_skb->data;
 	event_id = le16_to_cpu(event->event_id);
 	event_len = le16_to_cpu(event->mhdr.len);
 
-	if (likely(event->vifid < QTNF_MAX_INTF)) {
-		vif = &mac->iflist[event->vifid];
-	} else {
+	if (event->vifid >= QTNF_MAX_INTF) {
 		pr_err("invalid vif(%u)\n", event->vifid);
 		return -EINVAL;
 	}
 
+	vifid = array_index_nospec(event->vifid, QTNF_MAX_INTF);
+	vif = &mac->iflist[vifid];
+
 	switch (event_id) {
 	case QLINK_EVENT_STA_ASSOCIATED:
 		ret = qtnf_event_handle_sta_assoc(mac, vif, (const void *)event,

drivers/net/wireless/quantenna/qtnfmac/pcie/pearl_pcie.c

@@ -593,7 +593,7 @@ static int qtnf_pcie_skb_send(struct qtnf_bus *bus, struct sk_buff *skb)
 	priv->tx_bd_w_index = i;
 
 tx_done:
-	if (ret && skb) {
+	if (ret) {
 		pr_err_ratelimited("drop skb\n");
 		if (skb->dev)
 			skb->dev->stats.tx_dropped++;