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FAILED: patch "[PATCH] net: lan78xx: Fix race in tx pending skb size calculation" failed to apply to 4.4-stable tree

PATCH [email protected] 1 participant 1 message Jul 19, 2018

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Network drivers Stable branch USB networking drivers USB LAN78XX Ethernet driver
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The patch below does not apply to the 4.4-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

Quoted 1 line

From dea39aca1d7aef1e2b95b07edeacf04cc8863a2e Mon Sep 17 00:00:00 2001

From: Stefan Wahren <[email protected]>
Date: Sun, 15 Jul 2018 21:53:20 +0200
Subject: [PATCH] net: lan78xx: Fix race in tx pending skb size calculation

The skb size calculation in lan78xx_tx_bh is in race with the start_xmit, which could lead to rare kernel oopses. So protect the whole skb walk with a spin lock. As a benefit we can unlink the skb directly.

This patch was tested on Raspberry Pi 3B+

Link https://github.com/raspberrypi/linux/issues/2608
Fixes 55d7de9de6c3 ("Microchip's LAN7800 family USB 2/3 to 10/100/1000 Ethernet")
Cc stable <[email protected]>
Signed-off-by Floris Bos <[email protected]>
Signed-off-by Stefan Wahren <[email protected]>
Signed-off-by David S. Miller <[email protected]>
drivers/net/usb/lan78xx.c +4 -1
index 2e4130746c40..ed10d49eb5e0 100644
@@ -3344,6 +3344,7 @@ static void lan78xx_tx_bh(struct lan78xx_net *dev)
 	pkt_cnt = 0;
 	count = 0;
 	length = 0;
+	spin_lock_irqsave(&tqp->lock, flags);
 	for (skb = tqp->next; pkt_cnt < tqp->qlen; skb = skb->next) {
 		if (skb_is_gso(skb)) {
 			if (pkt_cnt) {

@@ -3352,7 +3353,8 @@ static void lan78xx_tx_bh(struct lan78xx_net *dev)
 			}
 			count = 1;
 			length = skb->len - TX_OVERHEAD;
-			skb2 = skb_dequeue(tqp);
+			__skb_unlink(skb, tqp);
+			spin_unlock_irqrestore(&tqp->lock, flags);
 			goto gso_skb;
 		}
 

@@ -3361,6 +3363,7 @@ static void lan78xx_tx_bh(struct lan78xx_net *dev)
 		skb_totallen = skb->len + roundup(skb_totallen, sizeof(u32));
 		pkt_cnt++;
 	}
+	spin_unlock_irqrestore(&tqp->lock, flags);
 
 	/* copy to a single skb */
 	skb = alloc_skb(skb_totallen, GFP_ATOMIC);