linux-kernel - Re: [PATCH] pstore/ram: Add ramoops_register

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Date:   Tue, 22 Jan 2019 14:55:16 +1300
From:   Kees Cook <keescook@...omium.org>
To:     Yue Hu <huyue2@...ong.com>
Cc:     Anton Vorontsov <anton@...msg.org>,
        Colin Cross <ccross@...roid.com>,
        Tony Luck <tony.luck@...el.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] pstore/ram: Add ramoops_register_dummy failure process

On Mon, Jan 21, 2019 at 9:42 PM Yue Hu <huyue2@...ong.com> wrote:
>
> From 0888dbf0e3ac4a6a8a6307e97d003e8deb9cc6db Mon Sep 17 00:00:00 2001
> From: Yue Hu <huyue2@...ong.com>
> Date: Mon, 21 Jan 2019 14:30:19 +0800
> Subject: [PATCH] pstore/ram: Add ramoops_register_dummy failure process
>
> If create dummy/dummy_data failed, platform_driver_register()
> could also return 0 which leads to successful ramoops_init().
> This logic is not reasonable, it should tell kernel ramoops is
> failed. This change can also avoid duplicated ramoops dummy
> unregister and remove some unnecessary messages too.

No, this is working as intended (perhaps this code needs better
comments). If there is no module parameters, they may yet still be a
custom platform driver (see
drivers/platform/chrome/chromeos_pstore.c), or device tree entry (see
Documentation/admin-guide/ramoops.rst).

-Kees

>
> Signed-off-by: Yue Hu <huyue2@...ong.com>
> ---
>  fs/pstore/ram.c | 20 ++++++++++----------
>  1 file changed, 10 insertions(+), 10 deletions(-)
>
> diff --git a/fs/pstore/ram.c b/fs/pstore/ram.c
> index 64a51cd..7fb97aa 100644
> --- a/fs/pstore/ram.c
> +++ b/fs/pstore/ram.c
> @@ -905,7 +905,7 @@ static inline void ramoops_unregister_dummy(void)
>         dummy_data = NULL;
>  }
>
> -static void __init ramoops_register_dummy(void)
> +static int __init ramoops_register_dummy(void)
>  {
>         /*
>          * Prepare a dummy platform data structure to carry the module
> @@ -913,15 +913,13 @@ static void __init ramoops_register_dummy(void)
>          * parameters, and we can skip this.
>          */
>         if (!mem_size)
> -               return;
> +               return -EINVAL;
>
>         pr_info("using module parameters\n");
>
>         dummy_data = kzalloc(sizeof(*dummy_data), GFP_KERNEL);
> -       if (!dummy_data) {
> -               pr_info("could not allocate pdata\n");
> -               return;
> -       }
> +       if (!dummy_data)
> +               return -ENOMEM;
>
>         dummy_data->mem_size = mem_size;
>         dummy_data->mem_address = mem_address;
> @@ -942,18 +940,20 @@ static void __init ramoops_register_dummy(void)
>         dummy = platform_device_register_data(NULL, "ramoops", -1,
>                         dummy_data, sizeof(struct ramoops_platform_data));
>         if (IS_ERR(dummy)) {
> -               pr_info("could not create platform device: %ld\n",
> -                       PTR_ERR(dummy));
> -               dummy = NULL;
>                 ramoops_unregister_dummy();
> +               return PTR_ERR(dummy);
>         }
> +       return 0;
>  }
>
>  static int __init ramoops_init(void)
>  {
>         int ret;
>
> -       ramoops_register_dummy();
> +       ret = ramoops_register_dummy();
> +       if (ret)
> +               return ret;
> +
>         ret = platform_driver_register(&ramoops_driver);
>         if (ret != 0)
>                 ramoops_unregister_dummy();
> --
> 1.9.1
>
>
>
>


-- 
Kees Cook