linux-kernel - [PATCH 4.9 076/103] brcmfmac: Ensure pointer correctly set if skb data location changes

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Message-Id: <20170511141216.618383162@linuxfoundation.org>
Date:   Thu, 11 May 2017 16:12:45 +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,
        James Hughes <james.hughes@...pberrypi.org>,
        Arend van Spriel <arend.vanspriel@...adcom.com>,
        Kalle Valo <kvalo@...eaurora.org>
Subject: [PATCH 4.9 076/103] brcmfmac: Ensure pointer correctly set if skb data location changes

4.9-stable review patch.  If anyone has any objections, please let me know.

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

From: James Hughes <james.hughes@...pberrypi.org>

commit 455a1eb4654c24560eb9dfc634f29cba3d87601e upstream.

The incoming skb header may be resized if header space is
insufficient, which might change the data adddress in the skb.
Ensure that a cached pointer to that data is correctly set by
moving assignment to after any possible changes.

Signed-off-by: James Hughes <james.hughes@...pberrypi.org>
Acked-by: Arend van Spriel <arend.vanspriel@...adcom.com>
Signed-off-by: Kalle Valo <kvalo@...eaurora.org>
Signed-off-by: Arend van Spriel <arend.vanspriel@...adcom.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/net/wireless/broadcom/brcm80211/brcmfmac/core.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/core.c
+++ b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/core.c
@@ -198,7 +198,7 @@ static netdev_tx_t brcmf_netdev_start_xm
 	int ret;
 	struct brcmf_if *ifp = netdev_priv(ndev);
 	struct brcmf_pub *drvr = ifp->drvr;
-	struct ethhdr *eh = (struct ethhdr *)(skb->data);
+	struct ethhdr *eh;
 
 	brcmf_dbg(DATA, "Enter, bsscfgidx=%d\n", ifp->bsscfgidx);
 
@@ -236,6 +236,8 @@ static netdev_tx_t brcmf_netdev_start_xm
 		goto done;
 	}
 
+	eh = (struct ethhdr *)(skb->data);
+
 	if (eh->h_proto == htons(ETH_P_PAE))
 		atomic_inc(&ifp->pend_8021x_cnt);