[PATCH] brcmfmac: Ensure pointer correctly set if skb data location changes

[PATCH] brcmfmac: Ensure pointer correctly set if skb data location changes

[James Hughes]

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

diff --git a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/core.c b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/core.c
index 5eaac13e2317..934fe00e28a0 100644
--- 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_xmit(struct sk_buff *skb,
 	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);
 
@@ -229,6 +229,8 @@ static netdev_tx_t brcmf_netdev_start_xmit(struct sk_buff *skb,
 		}
 	}
 
+	eh = (struct ethhdr *)(skb->data);
+
 	/* validate length for ether packet */
 	if (skb->len < sizeof(*eh)) {
 		ret = -EINVAL;
-- 
2.11.0

Re: [PATCH] brcmfmac: Ensure pointer correctly set if skb data location changes

[Arend van Spriel]

On 4/24/2017 12:52 PM, James Hughes wrote:
> 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.

Thanks, James

Minor nit below...

You may add my acknowledgement:

Acked-by: Arend van Spriel <arend.vanspriel@broadcom.com>
> Signed-off-by: James Hughes <james.hughes@raspberrypi.org>
> ---
>   drivers/net/wireless/broadcom/brcm80211/brcmfmac/core.c | 4 +++-
>   1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/wireless/broadcom/brcm80211/brcmfmac/core.c b/drivers/net/wireless/broadcom/brcm80211/brcmfmac/core.c

[...]

> @@ -229,6 +229,8 @@ static netdev_tx_t brcmf_netdev_start_xmit(struct sk_buff *skb,
>   		}
>   	}
>   
> +	eh = (struct ethhdr *)(skb->data);
> +

Please move after the length validation below.

Regards,
Arend

>   	/* validate length for ether packet */
>   	if (skb->len < sizeof(*eh)) {
>   		ret = -EINVAL;
>