linux-kernel - Re: [PATCH] acpi: Fix use-after-free in acpi

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Message-ID: <CAJZ5v0i2RYpw-rxvGWXzetiaSO34EH6x3TN5-O2npZM25Kww7w@mail.gmail.com>
Date:   Wed, 25 Nov 2020 16:53:16 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Youling Tang <tangyouling@...ngson.cn>
Cc:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Len Brown <lenb@...nel.org>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] acpi: Fix use-after-free in acpi_ipmi.c

On Tue, Nov 24, 2020 at 1:51 PM Youling Tang <tangyouling@...ngson.cn> wrote:
>
> kfree() has been called inside put_device so anther kfree would cause a
> use-after-free bug.
>
> Signed-off-by: Youling Tang <tangyouling@...ngson.cn>
> ---
>  drivers/acpi/acpi_ipmi.c | 2 --
>  1 file changed, 2 deletions(-)
>
> diff --git a/drivers/acpi/acpi_ipmi.c b/drivers/acpi/acpi_ipmi.c
> index 9d6c0fc..72902b6 100644
> --- a/drivers/acpi/acpi_ipmi.c
> +++ b/drivers/acpi/acpi_ipmi.c
> @@ -130,7 +130,6 @@ ipmi_dev_alloc(int iface, struct device *dev, acpi_handle handle)
>                                ipmi_device, &user);
>         if (err) {
>                 put_device(dev);
> -               kfree(ipmi_device);

dev doesn't point to the same object in memory as ipmi_device, though,
if I'm not mistaken.

Please double check that and resend the patch if you are sure that it
is correct.

>                 return NULL;
>         }
>         ipmi_device->user_interface = user;
> @@ -142,7 +141,6 @@ static void ipmi_dev_release(struct acpi_ipmi_device *ipmi_device)
>  {
>         ipmi_destroy_user(ipmi_device->user_interface);
>         put_device(ipmi_device->dev);
> -       kfree(ipmi_device);
>  }
>
>  static void ipmi_dev_release_kref(struct kref *kref)
> --
> 2.1.0
>