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2023-12-08 01573e231f18eb2d99162747186f59511f56b64d

 kernel/drivers/net/wan/hdlc_fr.c
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..
@@ -1,12 +1,9 @@
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+// SPDX-License-Identifier: GPL-2.0-only
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 /*
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  * Generic HDLC support routines for Linux
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  * Frame Relay support
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  *
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  * Copyright (C) 1999 - 2006 Krzysztof Halasa <khc@pm.waw.pl>
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- *
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- * This program is free software; you can redistribute it and/or modify it
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- * under the terms of version 2 of the GNU General Public License
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- * as published by the Free Software Foundation.
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  *
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8
 
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9
             Theory of PVC state
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@@ -274,10 +271,8 @@
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 }
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272
 
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-static int fr_hard_header(struct sk_buff **skb_p, u16 dlci)
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+static int fr_hard_header(struct sk_buff *skb, u16 dlci)
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 {
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-	struct sk_buff *skb = *skb_p;
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-
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 	if (!skb->dev) { /* Control packets */
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 		switch (dlci) {
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 		case LMI_CCITT_ANSI_DLCI:
..
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@@ -319,13 +314,6 @@
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 		}
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315
 
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 	} else if (skb->dev->type == ARPHRD_ETHER) {
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-		if (skb_headroom(skb) < 10) {
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-			struct sk_buff *skb2 = skb_realloc_headroom(skb, 10);
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-			if (!skb2)
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-				return -ENOBUFS;
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-			dev_kfree_skb(skb);
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-			skb = *skb_p = skb2;
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-		}
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 		skb_push(skb, 10);
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 		skb->data[3] = FR_PAD;
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 		skb->data[4] = NLPID_SNAP;
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@@ -419,38 +407,49 @@
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 {
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 	struct pvc_device *pvc = dev->ml_priv;
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409
 
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-	if (pvc->state.active) {
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-		if (dev->type == ARPHRD_ETHER) {
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-			int pad = ETH_ZLEN - skb->len;
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-			if (pad > 0) { /* Pad the frame with zeros */
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-				int len = skb->len;
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-				if (skb_tailroom(skb) < pad)
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-					if (pskb_expand_head(skb, 0, pad,
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-							     GFP_ATOMIC)) {
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-						dev->stats.tx_dropped++;
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-						dev_kfree_skb(skb);
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-						return NETDEV_TX_OK;
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-					}
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-				skb_put(skb, pad);
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-				memset(skb->data + len, 0, pad);
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-			}
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-		}
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-		skb->dev = dev;
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-		if (!fr_hard_header(&skb, pvc->dlci)) {
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-			dev->stats.tx_bytes += skb->len;
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-			dev->stats.tx_packets++;
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-			if (pvc->state.fecn) /* TX Congestion counter */
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-				dev->stats.tx_compressed++;
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-			skb->dev = pvc->frad;
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-			skb->protocol = htons(ETH_P_HDLC);
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-			skb_reset_network_header(skb);
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-			dev_queue_xmit(skb);
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-			return NETDEV_TX_OK;
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+	if (!pvc->state.active)
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+		goto drop;
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+
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+	if (dev->type == ARPHRD_ETHER) {
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+		int pad = ETH_ZLEN - skb->len;
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+
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+		if (pad > 0) { /* Pad the frame with zeros */
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+			if (__skb_pad(skb, pad, false))
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+				goto drop;
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+			skb_put(skb, pad);
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 		}
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 	}
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422
 
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+	/* We already requested the header space with dev->needed_headroom.
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+	 * So this is just a protection in case the upper layer didn't take
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+	 * dev->needed_headroom into consideration.
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+	 */
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+	if (skb_headroom(skb) < 10) {
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+		struct sk_buff *skb2 = skb_realloc_headroom(skb, 10);
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+
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+		if (!skb2)
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+			goto drop;
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+		dev_kfree_skb(skb);
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+		skb = skb2;
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+	}
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+
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+	skb->dev = dev;
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+	if (fr_hard_header(skb, pvc->dlci))
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+		goto drop;
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+
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+	dev->stats.tx_bytes += skb->len;
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+	dev->stats.tx_packets++;
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+	if (pvc->state.fecn) /* TX Congestion counter */
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+		dev->stats.tx_compressed++;
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+	skb->dev = pvc->frad;
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+	skb->protocol = htons(ETH_P_HDLC);
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+	skb_reset_network_header(skb);
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+	dev_queue_xmit(skb);
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+	return NETDEV_TX_OK;
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+
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+drop:
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 	dev->stats.tx_dropped++;
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-	dev_kfree_skb(skb);
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+	kfree_skb(skb);
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 	return NETDEV_TX_OK;
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 }
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455
 
..
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@@ -503,9 +502,9 @@
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 	memset(skb->data, 0, len);
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 	skb_reserve(skb, 4);
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 	if (lmi == LMI_CISCO) {
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-		fr_hard_header(&skb, LMI_CISCO_DLCI);
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+		fr_hard_header(skb, LMI_CISCO_DLCI);
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 	} else {
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-		fr_hard_header(&skb, LMI_CCITT_ANSI_DLCI);
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+		fr_hard_header(skb, LMI_CCITT_ANSI_DLCI);
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 	}
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 	data = skb_tail_pointer(skb);
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 	data[i++] = LMI_CALLREF;