[PATCH] moxart: fix potential use-after-free on remove path

[PATCH] moxart: fix potential use-after-free on remove path

[Greg Kroah-Hartman]

It was reported that the mmc host structure could be accessed after it
was freed in moxart_remove(), so fix this by saving the base register of
the device and using it instead of the pointer dereference.

Cc: Ulf Hansson <ulf.hansson@linaro.org>
Cc: Xiyu Yang <xiyuyang19@fudan.edu.cn>
Cc: Xin Xiong <xiongx18@fudan.edu.cn>
Cc: Xin Tan <tanxin.ctf@gmail.com>
Cc: Tony Lindgren <tony@atomide.com>
Cc: Yang Li <yang.lee@linux.alibaba.com>
Cc: linux-mmc@vger.kernel.org
Cc: stable <stable@vger.kernel.org>
Reported-by: whitehat002 <hackyzh002@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/mmc/host/moxart-mmc.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/mmc/host/moxart-mmc.c b/drivers/mmc/host/moxart-mmc.c
index 16d1c7a43d33..f5d96940a9b8 100644
--- a/drivers/mmc/host/moxart-mmc.c
+++ b/drivers/mmc/host/moxart-mmc.c
@@ -697,6 +697,7 @@ static int moxart_remove(struct platform_device *pdev)
 {
 	struct mmc_host *mmc = dev_get_drvdata(&pdev->dev);
 	struct moxart_host *host = mmc_priv(mmc);
+	void __iomem *base = host->base;
 
 	dev_set_drvdata(&pdev->dev, NULL);
 
@@ -707,10 +708,10 @@ static int moxart_remove(struct platform_device *pdev)
 	mmc_remove_host(mmc);
 	mmc_free_host(mmc);
 
-	writel(0, host->base + REG_INTERRUPT_MASK);
-	writel(0, host->base + REG_POWER_CONTROL);
-	writel(readl(host->base + REG_CLOCK_CONTROL) | CLK_OFF,
-	       host->base + REG_CLOCK_CONTROL);
+	writel(0, base + REG_INTERRUPT_MASK);
+	writel(0, base + REG_POWER_CONTROL);
+	writel(readl(base + REG_CLOCK_CONTROL) | CLK_OFF,
+	       base + REG_CLOCK_CONTROL);
 
 	return 0;
 }
-- 
2.34.1

Re: [PATCH] moxart: fix potential use-after-free on remove path

[Ulf Hansson]

On Fri, 14 Jan 2022 at 08:59, Greg Kroah-Hartman
<gregkh@linuxfoundation.org> wrote:
>
> It was reported that the mmc host structure could be accessed after it
> was freed in moxart_remove(), so fix this by saving the base register of
> the device and using it instead of the pointer dereference.
>
> Cc: Ulf Hansson <ulf.hansson@linaro.org>
> Cc: Xiyu Yang <xiyuyang19@fudan.edu.cn>
> Cc: Xin Xiong <xiongx18@fudan.edu.cn>
> Cc: Xin Tan <tanxin.ctf@gmail.com>
> Cc: Tony Lindgren <tony@atomide.com>
> Cc: Yang Li <yang.lee@linux.alibaba.com>
> Cc: linux-mmc@vger.kernel.org
> Cc: stable <stable@vger.kernel.org>
> Reported-by: whitehat002 <hackyzh002@gmail.com>
> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> ---
>  drivers/mmc/host/moxart-mmc.c | 9 +++++----
>  1 file changed, 5 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/mmc/host/moxart-mmc.c b/drivers/mmc/host/moxart-mmc.c
> index 16d1c7a43d33..f5d96940a9b8 100644
> --- a/drivers/mmc/host/moxart-mmc.c
> +++ b/drivers/mmc/host/moxart-mmc.c
> @@ -697,6 +697,7 @@ static int moxart_remove(struct platform_device *pdev)
>  {
>         struct mmc_host *mmc = dev_get_drvdata(&pdev->dev);
>         struct moxart_host *host = mmc_priv(mmc);
> +       void __iomem *base = host->base;
>
>         dev_set_drvdata(&pdev->dev, NULL);
>
> @@ -707,10 +708,10 @@ static int moxart_remove(struct platform_device *pdev)
>         mmc_remove_host(mmc);
>         mmc_free_host(mmc);
>
> -       writel(0, host->base + REG_INTERRUPT_MASK);
> -       writel(0, host->base + REG_POWER_CONTROL);
> -       writel(readl(host->base + REG_CLOCK_CONTROL) | CLK_OFF,
> -              host->base + REG_CLOCK_CONTROL);

Rather than doing it like this, I think it would be easier to move
mmc_free_host() below this part. That's usually what mmc host drivers
do clean up things in ->remove().

> +       writel(0, base + REG_INTERRUPT_MASK);
> +       writel(0, base + REG_POWER_CONTROL);
> +       writel(readl(base + REG_CLOCK_CONTROL) | CLK_OFF,
> +              base + REG_CLOCK_CONTROL);
>
>         return 0;
>  }

Kind regards
Uffe

Re: [PATCH] moxart: fix potential use-after-free on remove path

[Greg Kroah-Hartman]

On Fri, Jan 21, 2022 at 01:41:27PM +0100, Ulf Hansson wrote:
> On Fri, 14 Jan 2022 at 08:59, Greg Kroah-Hartman
> <gregkh@linuxfoundation.org> wrote:
> >
> > It was reported that the mmc host structure could be accessed after it
> > was freed in moxart_remove(), so fix this by saving the base register of
> > the device and using it instead of the pointer dereference.
> >
> > Cc: Ulf Hansson <ulf.hansson@linaro.org>
> > Cc: Xiyu Yang <xiyuyang19@fudan.edu.cn>
> > Cc: Xin Xiong <xiongx18@fudan.edu.cn>
> > Cc: Xin Tan <tanxin.ctf@gmail.com>
> > Cc: Tony Lindgren <tony@atomide.com>
> > Cc: Yang Li <yang.lee@linux.alibaba.com>
> > Cc: linux-mmc@vger.kernel.org
> > Cc: stable <stable@vger.kernel.org>
> > Reported-by: whitehat002 <hackyzh002@gmail.com>
> > Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> > ---
> >  drivers/mmc/host/moxart-mmc.c | 9 +++++----
> >  1 file changed, 5 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/mmc/host/moxart-mmc.c b/drivers/mmc/host/moxart-mmc.c
> > index 16d1c7a43d33..f5d96940a9b8 100644
> > --- a/drivers/mmc/host/moxart-mmc.c
> > +++ b/drivers/mmc/host/moxart-mmc.c
> > @@ -697,6 +697,7 @@ static int moxart_remove(struct platform_device *pdev)
> >  {
> >         struct mmc_host *mmc = dev_get_drvdata(&pdev->dev);
> >         struct moxart_host *host = mmc_priv(mmc);
> > +       void __iomem *base = host->base;
> >
> >         dev_set_drvdata(&pdev->dev, NULL);
> >
> > @@ -707,10 +708,10 @@ static int moxart_remove(struct platform_device *pdev)
> >         mmc_remove_host(mmc);
> >         mmc_free_host(mmc);
> >
> > -       writel(0, host->base + REG_INTERRUPT_MASK);
> > -       writel(0, host->base + REG_POWER_CONTROL);
> > -       writel(readl(host->base + REG_CLOCK_CONTROL) | CLK_OFF,
> > -              host->base + REG_CLOCK_CONTROL);
> 
> Rather than doing it like this, I think it would be easier to move
> mmc_free_host() below this part. That's usually what mmc host drivers
> do clean up things in ->remove().
> 
> > +       writel(0, base + REG_INTERRUPT_MASK);
> > +       writel(0, base + REG_POWER_CONTROL);
> > +       writel(readl(base + REG_CLOCK_CONTROL) | CLK_OFF,
> > +              base + REG_CLOCK_CONTROL);
> >

Ok, I can do that, I didn't know if it would cause any functionality
changes, so I was trying to preserve the same logic that the driver
currently has.

Do you have this device to test this with?

thanks,

greg k-h

Re: [PATCH] moxart: fix potential use-after-free on remove path

[Ulf Hansson]

On Fri, 21 Jan 2022 at 14:54, Greg Kroah-Hartman
<gregkh@linuxfoundation.org> wrote:
>
> On Fri, Jan 21, 2022 at 01:41:27PM +0100, Ulf Hansson wrote:
> > On Fri, 14 Jan 2022 at 08:59, Greg Kroah-Hartman
> > <gregkh@linuxfoundation.org> wrote:
> > >
> > > It was reported that the mmc host structure could be accessed after it
> > > was freed in moxart_remove(), so fix this by saving the base register of
> > > the device and using it instead of the pointer dereference.
> > >
> > > Cc: Ulf Hansson <ulf.hansson@linaro.org>
> > > Cc: Xiyu Yang <xiyuyang19@fudan.edu.cn>
> > > Cc: Xin Xiong <xiongx18@fudan.edu.cn>
> > > Cc: Xin Tan <tanxin.ctf@gmail.com>
> > > Cc: Tony Lindgren <tony@atomide.com>
> > > Cc: Yang Li <yang.lee@linux.alibaba.com>
> > > Cc: linux-mmc@vger.kernel.org
> > > Cc: stable <stable@vger.kernel.org>
> > > Reported-by: whitehat002 <hackyzh002@gmail.com>
> > > Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> > > ---
> > >  drivers/mmc/host/moxart-mmc.c | 9 +++++----
> > >  1 file changed, 5 insertions(+), 4 deletions(-)
> > >
> > > diff --git a/drivers/mmc/host/moxart-mmc.c b/drivers/mmc/host/moxart-mmc.c
> > > index 16d1c7a43d33..f5d96940a9b8 100644
> > > --- a/drivers/mmc/host/moxart-mmc.c
> > > +++ b/drivers/mmc/host/moxart-mmc.c
> > > @@ -697,6 +697,7 @@ static int moxart_remove(struct platform_device *pdev)
> > >  {
> > >         struct mmc_host *mmc = dev_get_drvdata(&pdev->dev);
> > >         struct moxart_host *host = mmc_priv(mmc);
> > > +       void __iomem *base = host->base;
> > >
> > >         dev_set_drvdata(&pdev->dev, NULL);
> > >
> > > @@ -707,10 +708,10 @@ static int moxart_remove(struct platform_device *pdev)
> > >         mmc_remove_host(mmc);
> > >         mmc_free_host(mmc);
> > >
> > > -       writel(0, host->base + REG_INTERRUPT_MASK);
> > > -       writel(0, host->base + REG_POWER_CONTROL);
> > > -       writel(readl(host->base + REG_CLOCK_CONTROL) | CLK_OFF,
> > > -              host->base + REG_CLOCK_CONTROL);
> >
> > Rather than doing it like this, I think it would be easier to move
> > mmc_free_host() below this part. That's usually what mmc host drivers
> > do clean up things in ->remove().
> >
> > > +       writel(0, base + REG_INTERRUPT_MASK);
> > > +       writel(0, base + REG_POWER_CONTROL);
> > > +       writel(readl(base + REG_CLOCK_CONTROL) | CLK_OFF,
> > > +              base + REG_CLOCK_CONTROL);
> > >
>
> Ok, I can do that, I didn't know if it would cause any functionality
> changes, so I was trying to preserve the same logic that the driver
> currently has.

Yes, but it's most likely just a simple mistake that was made by the
original author.

>
> Do you have this device to test this with?

No, I don't.

Although, I am confident that it should work fine too.

>
> thanks,
>
> greg k-h

Kind regards
Uffe

Re: [PATCH] moxart: fix potential use-after-free on remove path

[Greg Kroah-Hartman]

On Fri, Jan 21, 2022 at 03:24:05PM +0100, Ulf Hansson wrote:
> On Fri, 21 Jan 2022 at 14:54, Greg Kroah-Hartman
> <gregkh@linuxfoundation.org> wrote:
> >
> > On Fri, Jan 21, 2022 at 01:41:27PM +0100, Ulf Hansson wrote:
> > > On Fri, 14 Jan 2022 at 08:59, Greg Kroah-Hartman
> > > <gregkh@linuxfoundation.org> wrote:
> > > >
> > > > It was reported that the mmc host structure could be accessed after it
> > > > was freed in moxart_remove(), so fix this by saving the base register of
> > > > the device and using it instead of the pointer dereference.
> > > >
> > > > Cc: Ulf Hansson <ulf.hansson@linaro.org>
> > > > Cc: Xiyu Yang <xiyuyang19@fudan.edu.cn>
> > > > Cc: Xin Xiong <xiongx18@fudan.edu.cn>
> > > > Cc: Xin Tan <tanxin.ctf@gmail.com>
> > > > Cc: Tony Lindgren <tony@atomide.com>
> > > > Cc: Yang Li <yang.lee@linux.alibaba.com>
> > > > Cc: linux-mmc@vger.kernel.org
> > > > Cc: stable <stable@vger.kernel.org>
> > > > Reported-by: whitehat002 <hackyzh002@gmail.com>
> > > > Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> > > > ---
> > > >  drivers/mmc/host/moxart-mmc.c | 9 +++++----
> > > >  1 file changed, 5 insertions(+), 4 deletions(-)
> > > >
> > > > diff --git a/drivers/mmc/host/moxart-mmc.c b/drivers/mmc/host/moxart-mmc.c
> > > > index 16d1c7a43d33..f5d96940a9b8 100644
> > > > --- a/drivers/mmc/host/moxart-mmc.c
> > > > +++ b/drivers/mmc/host/moxart-mmc.c
> > > > @@ -697,6 +697,7 @@ static int moxart_remove(struct platform_device *pdev)
> > > >  {
> > > >         struct mmc_host *mmc = dev_get_drvdata(&pdev->dev);
> > > >         struct moxart_host *host = mmc_priv(mmc);
> > > > +       void __iomem *base = host->base;
> > > >
> > > >         dev_set_drvdata(&pdev->dev, NULL);
> > > >
> > > > @@ -707,10 +708,10 @@ static int moxart_remove(struct platform_device *pdev)
> > > >         mmc_remove_host(mmc);
> > > >         mmc_free_host(mmc);
> > > >
> > > > -       writel(0, host->base + REG_INTERRUPT_MASK);
> > > > -       writel(0, host->base + REG_POWER_CONTROL);
> > > > -       writel(readl(host->base + REG_CLOCK_CONTROL) | CLK_OFF,
> > > > -              host->base + REG_CLOCK_CONTROL);
> > >
> > > Rather than doing it like this, I think it would be easier to move
> > > mmc_free_host() below this part. That's usually what mmc host drivers
> > > do clean up things in ->remove().
> > >
> > > > +       writel(0, base + REG_INTERRUPT_MASK);
> > > > +       writel(0, base + REG_POWER_CONTROL);
> > > > +       writel(readl(base + REG_CLOCK_CONTROL) | CLK_OFF,
> > > > +              base + REG_CLOCK_CONTROL);
> > > >
> >
> > Ok, I can do that, I didn't know if it would cause any functionality
> > changes, so I was trying to preserve the same logic that the driver
> > currently has.
> 
> Yes, but it's most likely just a simple mistake that was made by the
> original author.
> 
> >
> > Do you have this device to test this with?
> 
> No, I don't.
> 
> Although, I am confident that it should work fine too.

Great, now sent v2:
	https://lore.kernel.org/r/20220127071638.4057899-1-gregkh@linuxfoundation.org