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Subject[PATCH 4.14 52/92] net: lan78xx: Fix race in tx pending skb size calculation
Date
4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Stefan Wahren <stefan.wahren@i2se.com>

commit dea39aca1d7aef1e2b95b07edeacf04cc8863a2e upstream.

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 <stable@vger.kernel.org>
Signed-off-by: Floris Bos <bos@je-eigen-domein.nl>
Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/net/usb/lan78xx.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)

--- a/drivers/net/usb/lan78xx.c
+++ b/drivers/net/usb/lan78xx.c
@@ -3197,6 +3197,7 @@ static void lan78xx_tx_bh(struct lan78xx
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) {
@@ -3205,7 +3206,8 @@ static void lan78xx_tx_bh(struct lan78xx
}
count = 1;
length = skb->len - TX_OVERHEAD;
- skb2 = skb_dequeue(tqp);
+ __skb_unlink(skb, tqp);
+ spin_unlock_irqrestore(&tqp->lock, flags);
goto gso_skb;
}

@@ -3214,6 +3216,7 @@ static void lan78xx_tx_bh(struct lan78xx
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);

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