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Date:   Sun, 10 Jun 2018 12:35:51 -0700 (PDT)
Message-Id: <20180610.123551.885190586229525170.davem@davemloft.net>
To:     Vadim.Lomovtsev@caviumnetworks.com
Cc:     rric@kernel.org, sgoutham@cavium.com,
        linux-arm-kernel@lists.infradead.org, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org, dnelson@redhat.com,
        Vadim.Lomovtsev@cavium.com
Subject: Re: [PATCH] net: thunderx: prevent concurrent data re-writing by
 nicvf_set_rx_mode
From:   David Miller <davem@davemloft.net>
In-Reply-To: <20180608092759.28059-1-Vadim.Lomovtsev@caviumnetworks.com>
References: <20180608092759.28059-1-Vadim.Lomovtsev@caviumnetworks.com>
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From: Vadim Lomovtsev <Vadim.Lomovtsev@caviumnetworks.com>
Date: Fri,  8 Jun 2018 02:27:59 -0700

> +	/* Save message data locally to prevent them from
> +	 * being overwritten by next ndo_set_rx_mode call().
> +	 */
> +	spin_lock(&nic->rx_mode_wq_lock);
> +	mode = vf_work->mode;
> +	mc = vf_work->mc;
> +	vf_work->mc = NULL;
> +	spin_unlock(&nic->rx_mode_wq_lock);

At the moment you drop this lock, the memory behind 'mc' can be
freed up by:

> +	spin_lock(&nic->rx_mode_wq_lock);
> +	kfree(nic->rx_mode_work.mc);

And you'll crash when you dereference it above via
__nicvf_set_rx_mode_task().