linux-kernel - [PATCH 4.4 004/312] staging: rtl8192u: Fix crash due to pointers being "confusing"

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Message-Id: <20200508123124.853211565@linuxfoundation.org>
Date:   Fri,  8 May 2020 14:29:55 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Ben Hutchings <ben@...adent.org.uk>
Subject: [PATCH 4.4 004/312] staging: rtl8192u: Fix crash due to pointers being "confusing"

From: Ben Hutchings <ben@...adent.org.uk>

commit c3f463484bdd0acd15abd5f92399041f79592d06 upstream.

There's no net_device stashed in skb->cb, there's a net_device * there.

To make it *really* clear, also change the write of the dev pointer
into skb->cb from a memcpy() to an assignment.

Fixes: 3fe563249374 ("staging: rtl8192u: r8192U_core.c: Cleaning up ...")
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/staging/rtl8192u/r8192U_core.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/drivers/staging/rtl8192u/r8192U_core.c
+++ b/drivers/staging/rtl8192u/r8192U_core.c
@@ -1050,7 +1050,7 @@ static void rtl8192_hard_data_xmit(struc
 
 	spin_lock_irqsave(&priv->tx_lock, flags);
 
-	memcpy((unsigned char *)(skb->cb), &dev, sizeof(dev));
+	*(struct net_device **)(skb->cb) = dev;
 	tcb_desc->bTxEnableFwCalcDur = 1;
 	skb_push(skb, priv->ieee80211->tx_headroom);
 	ret = rtl8192_tx(dev, skb);
@@ -1092,7 +1092,7 @@ static int rtl8192_hard_start_xmit(struc
 static void rtl8192_tx_isr(struct urb *tx_urb)
 {
 	struct sk_buff *skb = (struct sk_buff *)tx_urb->context;
-	struct net_device *dev = (struct net_device *)(skb->cb);
+	struct net_device *dev = *(struct net_device **)(skb->cb);
 	struct r8192_priv *priv = NULL;
 	cb_desc *tcb_desc = (cb_desc *)(skb->cb + MAX_DEV_ADDR_SIZE);
 	u8  queue_index = tcb_desc->queue_index;