2019-04-17 08:32:22

by Pan Bian

Subject: mmc: core: fix possible use after free of host

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")
Signed-off-by: Pan Bian <[email protected]>
---
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

2019-04-26 08:44:19

by Mathieu Malaterre

Subject: Re: mmc: core: fix possible use after free of host

On Wed, Apr 17, 2019 at 10:28 AM Pan Bian <[email protected]> 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 <[email protected]>
> ---
> 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
>
>

2019-04-29 10:47:00

by Ulf Hansson

Subject: Re: mmc: core: fix possible use after free of host

On Wed, 17 Apr 2019 at 10:29, Pan Bian <[email protected]> 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")
> Signed-off-by: Pan Bian <[email protected]>

Applied for next, thanks!

Kind regards
Uffe


> ---
> 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
>
>