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Date:   Tue, 8 Sep 2020 19:35:19 +0200
From:   Stefan Schmidt <stefan@...enfreihafen.org>
To:     Eric Dumazet <edumazet@...gle.com>,
        "David S . Miller" <davem@...emloft.net>
Cc:     netdev <netdev@...r.kernel.org>,
        Eric Dumazet <eric.dumazet@...il.com>,
        syzbot <syzkaller@...glegroups.com>,
        Alexander Aring <alex.aring@...il.com>,
        linux-wpan@...r.kernel.org
Subject: Re: [PATCH net] mac802154: tx: fix use-after-free

Hello Eric.

On 08.09.20 12:40, Eric Dumazet wrote:
> syzbot reported a bug in ieee802154_tx() [1]
> 
> A similar issue in ieee802154_xmit_worker() is also fixed in this patch.
> 

[ snip]

> 
> Fixes: 409c3b0c5f03 ("mac802154: tx: move stats tx increment")
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Reported-by: syzbot <syzkaller@...glegroups.com>
> Cc: Alexander Aring <alex.aring@...il.com>
> Cc: Stefan Schmidt <stefan@...enfreihafen.org>
> Cc: linux-wpan@...r.kernel.org
> ---
>   net/mac802154/tx.c | 8 +++++---
>   1 file changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/net/mac802154/tx.c b/net/mac802154/tx.c
> index ab52811523e992f33f0855cdb711a2752b602e15..c829e4a7532564d401c0d2d1f90f56c2fe030b2c 100644
> --- a/net/mac802154/tx.c
> +++ b/net/mac802154/tx.c
> @@ -34,11 +34,11 @@ void ieee802154_xmit_worker(struct work_struct *work)
>   	if (res)
>   		goto err_tx;
>   
> -	ieee802154_xmit_complete(&local->hw, skb, false);
> -
>   	dev->stats.tx_packets++;
>   	dev->stats.tx_bytes += skb->len;
>   
> +	ieee802154_xmit_complete(&local->hw, skb, false);
> +
>   	return;
>   
>   err_tx:
> @@ -78,6 +78,8 @@ ieee802154_tx(struct ieee802154_local *local, struct sk_buff *skb)
>   
>   	/* async is priority, otherwise sync is fallback */
>   	if (local->ops->xmit_async) {
> +		unsigned int len = skb->len;
> +
>   		ret = drv_xmit_async(local, skb);
>   		if (ret) {
>   			ieee802154_wake_queue(&local->hw);
> @@ -85,7 +87,7 @@ ieee802154_tx(struct ieee802154_local *local, struct sk_buff *skb)
>   		}
>   
>   		dev->stats.tx_packets++;
> -		dev->stats.tx_bytes += skb->len;
> +		dev->stats.tx_bytes += len;
>   	} else {
>   		local->tx_skb = skb;
>   		queue_work(local->workqueue, &local->tx_work);
> 

Thanks for catching this!

This patch has been applied to the wpan tree and will be
part of the next pull request to net. Thanks!

regards
Stefan Schmidt

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