[PATCH] wifi: wfx: fix possible NULL pointer dereference in wfx_set_mfp_ap()

[Dmitry Antipov <dmantipov@xxxxxxxxx>]

Since 'ieee80211_beacon_get()' can return NULL, 'wfx_set_mfp_ap()'
should check the return value before examining skb data. So convert
the latter to return an appropriate error code and propagate it to
return from 'wfx_start_ap()' as well. Compile tested only.

Signed-off-by: Dmitry Antipov <dmantipov@xxxxxxxxx>
---
 drivers/net/wireless/silabs/wfx/sta.c | 23 +++++++++++++----------
 1 file changed, 13 insertions(+), 10 deletions(-)

diff --git a/drivers/net/wireless/silabs/wfx/sta.c b/drivers/net/wireless/silabs/wfx/sta.c
index 1b6c158457b4..df100d8513ad 100644
--- a/drivers/net/wireless/silabs/wfx/sta.c
+++ b/drivers/net/wireless/silabs/wfx/sta.c
@@ -336,29 +336,35 @@ static int wfx_upload_ap_templates(struct wfx_vif *wvif)
 	return 0;
 }
 
-static void wfx_set_mfp_ap(struct wfx_vif *wvif)
+static int wfx_set_mfp_ap(struct wfx_vif *wvif)
 {
 	struct ieee80211_vif *vif = wvif_to_vif(wvif);
 	struct sk_buff *skb = ieee80211_beacon_get(wvif->wdev->hw, vif, 0);
 	const int ieoffset = offsetof(struct ieee80211_mgmt, u.beacon.variable);
-	const u16 *ptr = (u16 *)cfg80211_find_ie(WLAN_EID_RSN, skb->data + ieoffset,
-						 skb->len - ieoffset);
 	const int pairwise_cipher_suite_count_offset = 8 / sizeof(u16);
 	const int pairwise_cipher_suite_size = 4 / sizeof(u16);
 	const int akm_suite_size = 4 / sizeof(u16);
+	const u16 *ptr;
 
+	if (unlikely(!skb))
+		return -ENOMEM;
+
+	ptr = (u16 *)cfg80211_find_ie(WLAN_EID_RSN, skb->data + ieoffset,
+				      skb->len - ieoffset);
 	if (ptr) {
 		ptr += pairwise_cipher_suite_count_offset;
 		if (WARN_ON(ptr > (u16 *)skb_tail_pointer(skb)))
-			return;
+			return -EINVAL;
 		ptr += 1 + pairwise_cipher_suite_size * *ptr;
 		if (WARN_ON(ptr > (u16 *)skb_tail_pointer(skb)))
-			return;
+			return -EINVAL;
 		ptr += 1 + akm_suite_size * *ptr;
 		if (WARN_ON(ptr > (u16 *)skb_tail_pointer(skb)))
-			return;
+			return -EINVAL;
 		wfx_hif_set_mfp(wvif, *ptr & BIT(7), *ptr & BIT(6));
+		return 0;
 	}
+	return -EINVAL;
 }
 
 int wfx_start_ap(struct ieee80211_hw *hw, struct ieee80211_vif *vif,
@@ -374,10 +380,7 @@ int wfx_start_ap(struct ieee80211_hw *hw, struct ieee80211_vif *vif,
 	wvif = (struct wfx_vif *)vif->drv_priv;
 	wfx_upload_ap_templates(wvif);
 	ret = wfx_hif_start(wvif, &vif->bss_conf, wvif->channel);
-	if (ret > 0)
-		return -EIO;
-	wfx_set_mfp_ap(wvif);
-	return ret;
+	return ret > 0 ? -EIO : wfx_set_mfp_ap(wvif);
 }
 
 void wfx_stop_ap(struct ieee80211_hw *hw, struct ieee80211_vif *vif,
-- 
2.43.0