linux-kernel - Re: [PATCH] spmi: mediatek: Fix UAF on device remove

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Date:   Mon, 21 Aug 2023 11:35:32 +0800
From:   Chen-Yu Tsai <wenst@...omium.org>
To:     Yu-Che Cheng <giver@...omium.org>, Stephen Boyd <sboyd@...nel.org>
Cc:     James Lo <james.lo@...iatek.com>, Stephen Boyd <sboyd@...nel.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Fei Shao <fshao@...omium.org>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-mediatek@...ts.infradead.org
Subject: Re: [PATCH] spmi: mediatek: Fix UAF on device remove

On Mon, Jul 17, 2023 at 05:39:35PM +0800, Yu-Che Cheng wrote:
> The pmif driver data that contains the clocks is allocated along with
> spmi_controller.
> On device remove, spmi_controller will be freed first, and then devres
> , including the clocks, will be cleanup.
> This leads to UAF because putting the clocks will access the clocks in
> the pmif driver data, which is already freed along with spmi_controller.
> 
> This can be reproduced by enabling DEBUG_TEST_DRIVER_REMOVE and
> building the kernel with KASAN.
> 
> Fix the UAF issue by using unmanaged clk_bulk_get() and putting the
> clocks before freeing spmi_controller.
> 
> Reported-by: Fei Shao <fshao@...omium.org>
> Signed-off-by: Yu-Che Cheng <giver@...omium.org>

Reviewed-by: Chen-Yu Tsai <wenst@...omium.org>

Stephen, could you pick this up?

> ---
> 
>  drivers/spmi/spmi-mtk-pmif.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/spmi/spmi-mtk-pmif.c b/drivers/spmi/spmi-mtk-pmif.c
> index b3c991e1ea40..74b73f9bc222 100644
> --- a/drivers/spmi/spmi-mtk-pmif.c
> +++ b/drivers/spmi/spmi-mtk-pmif.c
> @@ -465,7 +465,7 @@ static int mtk_spmi_probe(struct platform_device *pdev)
>  	for (i = 0; i < arb->nclks; i++)
>  		arb->clks[i].id = pmif_clock_names[i];
>  
> -	err = devm_clk_bulk_get(&pdev->dev, arb->nclks, arb->clks);
> +	err = clk_bulk_get(&pdev->dev, arb->nclks, arb->clks);
>  	if (err) {
>  		dev_err(&pdev->dev, "Failed to get clocks: %d\n", err);
>  		goto err_put_ctrl;
> @@ -474,7 +474,7 @@ static int mtk_spmi_probe(struct platform_device *pdev)
>  	err = clk_bulk_prepare_enable(arb->nclks, arb->clks);
>  	if (err) {
>  		dev_err(&pdev->dev, "Failed to enable clocks: %d\n", err);
> -		goto err_put_ctrl;
> +		goto err_put_clks;
>  	}
>  
>  	ctrl->cmd = pmif_arb_cmd;
> @@ -498,6 +498,8 @@ static int mtk_spmi_probe(struct platform_device *pdev)
>  
>  err_domain_remove:
>  	clk_bulk_disable_unprepare(arb->nclks, arb->clks);
> +err_put_clks:
> +	clk_bulk_put(arb->nclks, arb->clks);
>  err_put_ctrl:
>  	spmi_controller_put(ctrl);
>  	return err;
> @@ -509,6 +511,7 @@ static void mtk_spmi_remove(struct platform_device *pdev)
>  	struct pmif *arb = spmi_controller_get_drvdata(ctrl);
>  
>  	clk_bulk_disable_unprepare(arb->nclks, arb->clks);
> +	clk_bulk_put(arb->nclks, arb->clks);
>  	spmi_controller_remove(ctrl);
>  	spmi_controller_put(ctrl);

Maybe we need devres versions of spmi_controller_alloc and
spmi_controller_add to avoid this in the future? I'm sure
drivers put all sorts of stuff in their private data.

ChenYu

>  }
> -- 
> 2.41.0.255.g8b1d071c50-goog
>