netdev - Re: [PATCH] dp83640: don't recieve time stamps twice

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Message-ID: <20170418201917.GA4428@localhost.localdomain>
Date:   Tue, 18 Apr 2017 22:19:17 +0200
From:   Richard Cochran <richardcochran@...il.com>
To:     Dan Carpenter <dan.carpenter@...cle.com>
Cc:     Stefan Sørensen 
        <stefan.sorensen@...ctralink.com>, Andrew Lunn <andrew@...n.ch>,
        Florian Fainelli <f.fainelli@...il.com>,
        netdev@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: Re: [PATCH] dp83640: don't recieve time stamps twice

On Tue, Apr 18, 2017 at 10:14:26PM +0300, Dan Carpenter wrote:
> This patch is prompted by a static checker warning about a potential
> use after free.  The concern is that netif_rx_ni() can free "skb" and we
> call it twice.

Right, the code already calls netif_rx_ni() in the list_for_each_safe()
loop just above, in the case that the shhwtstamps pointer has been set.
 
> When I look at the commit that added this, it looks like some stray
> lines were added accidentally.  It doesn't make sense to me that we
> would recieve the same data two times.  I asked the author but never
> recieved a response.

Hm, maybe the intent was to move the call to netif_rx_ni() outside of
the spin_lock_irqsave() region (which how I had it before Stefan's
changes).

But calling netif_rx_ni() twice is clearly wrong.

Thanks,
Richard