linux-kernel - Re: mmc: core: fix possible use after free of host

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Message-ID: <CA+7wUswSXNvLbYG4RxquH1rc9KmtCaE5N2iWe9K6SWG8MOnsdw@mail.gmail.com>
Date:   Fri, 26 Apr 2019 10:41:43 +0200
From:   Mathieu Malaterre <malat@...ian.org>
To:     Pan Bian <bianpan2016@....com>
Cc:     Ulf Hansson <ulf.hansson@...aro.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Shawn Lin <shawn.lin@...k-chips.com>,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>,
        Tony Lindgren <tony@...mide.com>, linux-mmc@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>,
        Heiner Kallweit <hkallweit1@...il.com>
Subject: Re: mmc: core: fix possible use after free of host

On Wed, Apr 17, 2019 at 10:28 AM Pan Bian <bianpan2016@....com> wrote:
>
> In the function mmc_alloc_host, the function put_device is called to
> release allocated resources when mmc_gpio_alloc fails. Finally, the
> function pointed by host->class_dev.class->dev_release (i.e.,
> mmc_host_classdev_release) is used to release resources including the
> host structure. However, after put_device, host is used and released
> again. Resulting in a use-after-free bug.
>
> Fixes: 1ed21719448("mmc: core: fix error path in mmc_host_alloc")

The original commit 1ed21719448 looks correct to me (see
mmc_host_classdev_release).

> Signed-off-by: Pan Bian <bianpan2016@....com>
> ---
>  drivers/mmc/core/host.c | 2 --
>  1 file changed, 2 deletions(-)
>
> diff --git a/drivers/mmc/core/host.c b/drivers/mmc/core/host.c
> index 3a4402a..f8ac567 100644
> --- a/drivers/mmc/core/host.c
> +++ b/drivers/mmc/core/host.c
> @@ -429,8 +429,6 @@ struct mmc_host *mmc_alloc_host(int extra, struct device *dev)
>
>         if (mmc_gpio_alloc(host)) {
>                 put_device(&host->class_dev);
> -               ida_simple_remove(&mmc_host_ida, host->index);
> -               kfree(host);
>                 return NULL;
>         }
>
> --
> 2.7.4
>
>