linux-kernel - Re: [PATCH] reset: hisilicon: fix potential NULL pointer dereference

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Message-ID: <153256235859.48062.6895683993866147909@swboyd.mtv.corp.google.com>
Date:   Wed, 25 Jul 2018 16:45:58 -0700
From:   Stephen Boyd <sboyd@...nel.org>
To:     "Gustavo A. R. Silva" <gustavo@...eddedor.com>,
        Jiancheng Xue <xuejiancheng@...ilicon.com>,
        Michael Turquette <mturquette@...libre.com>
Cc:     linux-clk@...r.kernel.org, linux-kernel@...r.kernel.org,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>
Subject: Re: [PATCH] reset: hisilicon: fix potential NULL pointer dereference

Quoting Gustavo A. R. Silva (2018-07-18 18:58:45)
> There is a potential execution path in which function
> platform_get_resource() returns NULL. If this happens,
> we will end up having a NULL pointer dereference.
> 
> Fix this by adding asanity check in order to avoid a
> NULL pointer dereference.
> 
> This code was detected with the help of Coccinelle.
> 
> Cc: stable@...r.kernel.org
> Fixes: 97b7129cd2af ("reset: hisilicon: change the definition of hisi_reset_init")
> Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>
> ---
>  drivers/clk/hisilicon/reset.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/clk/hisilicon/reset.c b/drivers/clk/hisilicon/reset.c
> index 2a5015c..5dfb48b 100644
> --- a/drivers/clk/hisilicon/reset.c
> +++ b/drivers/clk/hisilicon/reset.c
> @@ -109,6 +109,9 @@ struct hisi_reset_controller *hisi_reset_init(struct platform_device *pdev)
>                 return NULL;
>  
>         res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +       if (!res)
> +               return NULL;
> +
>         rstc->membase = devm_ioremap(&pdev->dev,
>                                 res->start, resource_size(res));

Why can't we use devm_ioremap_resource() here instead?