net: phy: micrel: Fix potential null pointer dereference

In lan8814_get_sig_rx() and lan8814_get_sig_tx() ptp_parse_header() may
return NULL as ptp_header due to abnormal packet type or corrupted packet.
Fix this bug by adding ptp_header check.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Fixes: ece19502 ("net: phy: micrel: 1588 support for LAN8814 phy")
Signed-off-by: Aleksandr Mishin <amishin@t-argos.ru>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://lore.kernel.org/r/20240329061631.33199-1-amishin@t-argos.ruSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/phy/micrel.c

@@ -2537,7 +2537,7 @@ static void lan8814_txtstamp(struct mii_timestamper *mii_ts,
 	}
 }
 
-static void lan8814_get_sig_rx(struct sk_buff *skb, u16 *sig)
+static bool lan8814_get_sig_rx(struct sk_buff *skb, u16 *sig)
 {
 	struct ptp_header *ptp_header;
 	u32 type;
@@ -2547,7 +2547,11 @@ static void lan8814_get_sig_rx(struct sk_buff *skb, u16 *sig)
 	ptp_header = ptp_parse_header(skb, type);
 	skb_pull_inline(skb, ETH_HLEN);
 
+	if (!ptp_header)
+		return false;
+
 	*sig = (__force u16)(ntohs(ptp_header->sequence_id));
+	return true;
 }
 
 static bool lan8814_match_rx_skb(struct kszphy_ptp_priv *ptp_priv,
@@ -2559,7 +2563,8 @@ static bool lan8814_match_rx_skb(struct kszphy_ptp_priv *ptp_priv,
 	bool ret = false;
 	u16 skb_sig;
 
-	lan8814_get_sig_rx(skb, &skb_sig);
+	if (!lan8814_get_sig_rx(skb, &skb_sig))
+		return ret;
 
 	/* Iterate over all RX timestamps and match it with the received skbs */
 	spin_lock_irqsave(&ptp_priv->rx_ts_lock, flags);
@@ -2834,7 +2839,7 @@ static int lan8814_ptpci_adjfine(struct ptp_clock_info *ptpci, long scaled_ppm)
 	return 0;
 }
 
-static void lan8814_get_sig_tx(struct sk_buff *skb, u16 *sig)
+static bool lan8814_get_sig_tx(struct sk_buff *skb, u16 *sig)
 {
 	struct ptp_header *ptp_header;
 	u32 type;
@@ -2842,7 +2847,11 @@ static void lan8814_get_sig_tx(struct sk_buff *skb, u16 *sig)
 	type = ptp_classify_raw(skb);
 	ptp_header = ptp_parse_header(skb, type);
 
+	if (!ptp_header)
+		return false;
+
 	*sig = (__force u16)(ntohs(ptp_header->sequence_id));
+	return true;
 }
 
 static void lan8814_match_tx_skb(struct kszphy_ptp_priv *ptp_priv,
@@ -2856,7 +2865,8 @@ static void lan8814_match_tx_skb(struct kszphy_ptp_priv *ptp_priv,
 
 	spin_lock_irqsave(&ptp_priv->tx_queue.lock, flags);
 	skb_queue_walk_safe(&ptp_priv->tx_queue, skb, skb_tmp) {
-		lan8814_get_sig_tx(skb, &skb_sig);
+		if (!lan8814_get_sig_tx(skb, &skb_sig))
+			continue;
 
 		if (memcmp(&skb_sig, &seq_id, sizeof(seq_id)))
 			continue;
@@ -2910,7 +2920,8 @@ static bool lan8814_match_skb(struct kszphy_ptp_priv *ptp_priv,
 
 	spin_lock_irqsave(&ptp_priv->rx_queue.lock, flags);
 	skb_queue_walk_safe(&ptp_priv->rx_queue, skb, skb_tmp) {
-		lan8814_get_sig_rx(skb, &skb_sig);
+		if (!lan8814_get_sig_rx(skb, &skb_sig))
+			continue;
 
 		if (memcmp(&skb_sig, &rx_ts->seq_id, sizeof(rx_ts->seq_id)))
 			continue;