[v3] fsi: Aspeed: Fix a potential double free

[PATCH v3] fsi: Aspeed: Fix a potential double free

Posted by Christophe JAILLET 4 years, 5 months ago

A struct device can never be devm_alloc()'ed.
Here, it is embedded in "struct fsi_master", and "struct fsi_master" is
embedded in "struct fsi_master_aspeed".

Since "struct device" is embedded, the data structure embedding it must be
released with the release function, as is already done here.

So use kzalloc() instead of devm_kzalloc() when allocating "aspeed" and
update all error handling branches accordingly.

This prevent a potential double free().

This also fix another issue if opb_readl() fails. Instead of a direct
return, it now jumps in the error handling path.

Fixes: 606397d67f41 ("fsi: Add ast2600 master driver")
Suggested-by: Greg KH <gregkh@linuxfoundation.org>
Suggested-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
---
v2: Keep the release function which is correct
    s/devm_kzalloc()/kzalloc()/ instead

v3: Update the error handling path to free "aspeed" [Guenter Roeck]
    Fix another issue when opb_readl() fails [Guenter Roeck]

I hope that fixing both issues in the same patch is ok. It makes no sense
to me not to update the goto to the correct label if opb_readl() fails.
---
 drivers/fsi/fsi-master-aspeed.c | 17 +++++++++++------
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/drivers/fsi/fsi-master-aspeed.c b/drivers/fsi/fsi-master-aspeed.c
index 8606e55c1721..0bed2fab8055 100644
--- a/drivers/fsi/fsi-master-aspeed.c
+++ b/drivers/fsi/fsi-master-aspeed.c
@@ -542,25 +542,28 @@ static int fsi_master_aspeed_probe(struct platform_device *pdev)
 		return rc;
 	}
 
-	aspeed = devm_kzalloc(&pdev->dev, sizeof(*aspeed), GFP_KERNEL);
+	aspeed = kzalloc(sizeof(*aspeed), GFP_KERNEL);
 	if (!aspeed)
 		return -ENOMEM;
 
 	aspeed->dev = &pdev->dev;
 
 	aspeed->base = devm_platform_ioremap_resource(pdev, 0);
-	if (IS_ERR(aspeed->base))
-		return PTR_ERR(aspeed->base);
+	if (IS_ERR(aspeed->base)) {
+		rc = PTR_ERR(aspeed->base);
+		goto err_free_aspeed;
+	}
 
 	aspeed->clk = devm_clk_get(aspeed->dev, NULL);
 	if (IS_ERR(aspeed->clk)) {
 		dev_err(aspeed->dev, "couldn't get clock\n");
-		return PTR_ERR(aspeed->clk);
+		rc = PTR_ERR(aspeed->clk);
+		goto err_free_aspeed;
 	}
 	rc = clk_prepare_enable(aspeed->clk);
 	if (rc) {
 		dev_err(aspeed->dev, "couldn't enable clock\n");
-		return rc;
+		goto err_free_aspeed;
 	}
 
 	rc = setup_cfam_reset(aspeed);
@@ -595,7 +598,7 @@ static int fsi_master_aspeed_probe(struct platform_device *pdev)
 	rc = opb_readl(aspeed, ctrl_base + FSI_MVER, &raw);
 	if (rc) {
 		dev_err(&pdev->dev, "failed to read hub version\n");
-		return rc;
+		goto err_release;
 	}
 
 	reg = be32_to_cpu(raw);
@@ -634,6 +637,8 @@ static int fsi_master_aspeed_probe(struct platform_device *pdev)
 
 err_release:
 	clk_disable_unprepare(aspeed->clk);
+err_free_aspeed:
+	kfree(aspeed);
 	return rc;
 }
 
-- 
2.32.0

Re: [PATCH v3] fsi: Aspeed: Fix a potential double free

Posted by Joel Stanley 4 years, 4 months ago

Hi Christophe,

Thanks for the patch.

On Sun, 9 Jan 2022 at 21:56, Christophe JAILLET
<christophe.jaillet@wanadoo.fr> wrote:
>
> A struct device can never be devm_alloc()'ed.
> Here, it is embedded in "struct fsi_master", and "struct fsi_master" is
> embedded in "struct fsi_master_aspeed".
>
> Since "struct device" is embedded, the data structure embedding it must be
> released with the release function, as is already done here.
>
> So use kzalloc() instead of devm_kzalloc() when allocating "aspeed" and
> update all error handling branches accordingly.

This looks like a problem with the design of the fsi master structure.
It's a common pattern to devm_alloc the platform devices as they are
probed, the fsi masters all embed a copy of struct fsi_master, which
as you say embeds struct device.

Can we learn from other bus drivers (eg i2c?) how we should lay out
these structures?




>
> This prevent a potential double free().
>
> This also fix another issue if opb_readl() fails. Instead of a direct
> return, it now jumps in the error handling path.
>
> Fixes: 606397d67f41 ("fsi: Add ast2600 master driver")
> Suggested-by: Greg KH <gregkh@linuxfoundation.org>
> Suggested-by: Guenter Roeck <linux@roeck-us.net>
> Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
> ---
> v2: Keep the release function which is correct
>     s/devm_kzalloc()/kzalloc()/ instead
>
> v3: Update the error handling path to free "aspeed" [Guenter Roeck]
>     Fix another issue when opb_readl() fails [Guenter Roeck]
>
> I hope that fixing both issues in the same patch is ok. It makes no sense
> to me not to update the goto to the correct label if opb_readl() fails.
> ---
>  drivers/fsi/fsi-master-aspeed.c | 17 +++++++++++------
>  1 file changed, 11 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/fsi/fsi-master-aspeed.c b/drivers/fsi/fsi-master-aspeed.c
> index 8606e55c1721..0bed2fab8055 100644
> --- a/drivers/fsi/fsi-master-aspeed.c
> +++ b/drivers/fsi/fsi-master-aspeed.c
> @@ -542,25 +542,28 @@ static int fsi_master_aspeed_probe(struct platform_device *pdev)
>                 return rc;
>         }
>
> -       aspeed = devm_kzalloc(&pdev->dev, sizeof(*aspeed), GFP_KERNEL);
> +       aspeed = kzalloc(sizeof(*aspeed), GFP_KERNEL);
>         if (!aspeed)
>                 return -ENOMEM;
>
>         aspeed->dev = &pdev->dev;
>
>         aspeed->base = devm_platform_ioremap_resource(pdev, 0);
> -       if (IS_ERR(aspeed->base))
> -               return PTR_ERR(aspeed->base);
> +       if (IS_ERR(aspeed->base)) {
> +               rc = PTR_ERR(aspeed->base);
> +               goto err_free_aspeed;
> +       }
>
>         aspeed->clk = devm_clk_get(aspeed->dev, NULL);
>         if (IS_ERR(aspeed->clk)) {
>                 dev_err(aspeed->dev, "couldn't get clock\n");
> -               return PTR_ERR(aspeed->clk);
> +               rc = PTR_ERR(aspeed->clk);
> +               goto err_free_aspeed;
>         }
>         rc = clk_prepare_enable(aspeed->clk);
>         if (rc) {
>                 dev_err(aspeed->dev, "couldn't enable clock\n");
> -               return rc;
> +               goto err_free_aspeed;
>         }
>
>         rc = setup_cfam_reset(aspeed);
> @@ -595,7 +598,7 @@ static int fsi_master_aspeed_probe(struct platform_device *pdev)
>         rc = opb_readl(aspeed, ctrl_base + FSI_MVER, &raw);
>         if (rc) {
>                 dev_err(&pdev->dev, "failed to read hub version\n");
> -               return rc;
> +               goto err_release;
>         }
>
>         reg = be32_to_cpu(raw);
> @@ -634,6 +637,8 @@ static int fsi_master_aspeed_probe(struct platform_device *pdev)
>
>  err_release:
>         clk_disable_unprepare(aspeed->clk);
> +err_free_aspeed:
> +       kfree(aspeed);
>         return rc;
>  }
>
> --
> 2.32.0
>

Re: [PATCH v3] fsi: Aspeed: Fix a potential double free

Posted by Christophe JAILLET 4 years, 4 months ago

Le 21/02/2022 à 10:24, Joel Stanley a écrit :
> Hi Christophe,
> 
> Thanks for the patch.
> 
> On Sun, 9 Jan 2022 at 21:56, Christophe JAILLET
> <christophe.jaillet@wanadoo.fr> wrote:
>>
>> A struct device can never be devm_alloc()'ed.
>> Here, it is embedded in "struct fsi_master", and "struct fsi_master" is
>> embedded in "struct fsi_master_aspeed".
>>
>> Since "struct device" is embedded, the data structure embedding it must be
>> released with the release function, as is already done here.
>>
>> So use kzalloc() instead of devm_kzalloc() when allocating "aspeed" and
>> update all error handling branches accordingly.
> 
> This looks like a problem with the design of the fsi master structure.
> It's a common pattern to devm_alloc the platform devices as they are
> probed, the fsi masters all embed a copy of struct fsi_master, which
> as you say embeds struct device.
> 
> Can we learn from other bus drivers (eg i2c?) how we should lay out
> these structures?
> 
Hi,
I won't do it myself.

This goes beyond my knowledge and without the possibility to test it, it 
would be just some random trial and error (as I did in the first broken 
version of this patch).

CJ

Re: [PATCH v3] fsi: Aspeed: Fix a potential double free

Posted by Guenter Roeck 4 years, 5 months ago

On 1/9/22 1:56 PM, Christophe JAILLET wrote:
> A struct device can never be devm_alloc()'ed.
> Here, it is embedded in "struct fsi_master", and "struct fsi_master" is
> embedded in "struct fsi_master_aspeed".
> 
> Since "struct device" is embedded, the data structure embedding it must be
> released with the release function, as is already done here.
> 
> So use kzalloc() instead of devm_kzalloc() when allocating "aspeed" and
> update all error handling branches accordingly.
> 
> This prevent a potential double free().
> 
> This also fix another issue if opb_readl() fails. Instead of a direct
> return, it now jumps in the error handling path.
> 
> Fixes: 606397d67f41 ("fsi: Add ast2600 master driver")
> Suggested-by: Greg KH <gregkh@linuxfoundation.org>
> Suggested-by: Guenter Roeck <linux@roeck-us.net>
> Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>

Reviewed-by: Guenter Roeck <linux@roeck-us.net>

> ---
> v2: Keep the release function which is correct
>      s/devm_kzalloc()/kzalloc()/ instead
> 
> v3: Update the error handling path to free "aspeed" [Guenter Roeck]
>      Fix another issue when opb_readl() fails [Guenter Roeck]
> 
> I hope that fixing both issues in the same patch is ok. It makes no sense
> to me not to update the goto to the correct label if opb_readl() fails.
> ---
>   drivers/fsi/fsi-master-aspeed.c | 17 +++++++++++------
>   1 file changed, 11 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/fsi/fsi-master-aspeed.c b/drivers/fsi/fsi-master-aspeed.c
> index 8606e55c1721..0bed2fab8055 100644
> --- a/drivers/fsi/fsi-master-aspeed.c
> +++ b/drivers/fsi/fsi-master-aspeed.c
> @@ -542,25 +542,28 @@ static int fsi_master_aspeed_probe(struct platform_device *pdev)
>   		return rc;
>   	}
>   
> -	aspeed = devm_kzalloc(&pdev->dev, sizeof(*aspeed), GFP_KERNEL);
> +	aspeed = kzalloc(sizeof(*aspeed), GFP_KERNEL);
>   	if (!aspeed)
>   		return -ENOMEM;
>   
>   	aspeed->dev = &pdev->dev;
>   
>   	aspeed->base = devm_platform_ioremap_resource(pdev, 0);
> -	if (IS_ERR(aspeed->base))
> -		return PTR_ERR(aspeed->base);
> +	if (IS_ERR(aspeed->base)) {
> +		rc = PTR_ERR(aspeed->base);
> +		goto err_free_aspeed;
> +	}
>   
>   	aspeed->clk = devm_clk_get(aspeed->dev, NULL);
>   	if (IS_ERR(aspeed->clk)) {
>   		dev_err(aspeed->dev, "couldn't get clock\n");
> -		return PTR_ERR(aspeed->clk);
> +		rc = PTR_ERR(aspeed->clk);
> +		goto err_free_aspeed;
>   	}
>   	rc = clk_prepare_enable(aspeed->clk);
>   	if (rc) {
>   		dev_err(aspeed->dev, "couldn't enable clock\n");
> -		return rc;
> +		goto err_free_aspeed;
>   	}
>   
>   	rc = setup_cfam_reset(aspeed);
> @@ -595,7 +598,7 @@ static int fsi_master_aspeed_probe(struct platform_device *pdev)
>   	rc = opb_readl(aspeed, ctrl_base + FSI_MVER, &raw);
>   	if (rc) {
>   		dev_err(&pdev->dev, "failed to read hub version\n");
> -		return rc;
> +		goto err_release;
>   	}
>   
>   	reg = be32_to_cpu(raw);
> @@ -634,6 +637,8 @@ static int fsi_master_aspeed_probe(struct platform_device *pdev)
>   
>   err_release:
>   	clk_disable_unprepare(aspeed->clk);
> +err_free_aspeed:
> +	kfree(aspeed);
>   	return rc;
>   }
>   
>