[PATCH 1/2] cxl: fix possible null-ptr-deref in cxl_guest_init_afu|adapter()

[PATCH 1/2] cxl: fix possible null-ptr-deref in cxl_guest_init_afu|adapter()

[Yang Yingliang]

If device_register() fails in cxl_register_afu|adapter(), the device
is not added, device_unregister() can not be called in the error path,
otherwise it will cause a null-ptr-deref because of removing not added
device.

As comment of device_register() says, it should use put_device() to give
up the reference in the error path. So split device_unregister() into
device_del() and put_device(), then goes to put dev when register fails.

Fixes: 14baf4d9c739 ("cxl: Add guest-specific code")
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
---
 drivers/misc/cxl/guest.c | 24 ++++++++++++++----------
 1 file changed, 14 insertions(+), 10 deletions(-)

diff --git a/drivers/misc/cxl/guest.c b/drivers/misc/cxl/guest.c
index 375f692ae9d6..fb95a2d5cef4 100644
--- a/drivers/misc/cxl/guest.c
+++ b/drivers/misc/cxl/guest.c
@@ -965,10 +965,10 @@ int cxl_guest_init_afu(struct cxl *adapter, int slice, struct device_node *afu_n
 	 * if it returns an error!
 	 */
 	if ((rc = cxl_register_afu(afu)))
-		goto err_put1;
+		goto err_put_dev;
 
 	if ((rc = cxl_sysfs_afu_add(afu)))
-		goto err_put1;
+		goto err_del_dev;
 
 	/*
 	 * pHyp doesn't expose the programming models supported by the
@@ -984,7 +984,7 @@ int cxl_guest_init_afu(struct cxl *adapter, int slice, struct device_node *afu_n
 		afu->modes_supported = CXL_MODE_DIRECTED;
 
 	if ((rc = cxl_afu_select_best_mode(afu)))
-		goto err_put2;
+		goto err_remove_sysfs;
 
 	adapter->afu[afu->slice] = afu;
 
@@ -1004,10 +1004,12 @@ int cxl_guest_init_afu(struct cxl *adapter, int slice, struct device_node *afu_n
 
 	return 0;
 
-err_put2:
+err_remove_sysfs:
 	cxl_sysfs_afu_remove(afu);
-err_put1:
-	device_unregister(&afu->dev);
+err_del_dev:
+	device_del(&afu->dev);
+err_put_dev:
+	put_device(&afu->dev);
 	free = false;
 	guest_release_serr_irq(afu);
 err2:
@@ -1141,18 +1143,20 @@ struct cxl *cxl_guest_init_adapter(struct device_node *np, struct platform_devic
 	 * even if it returns an error!
 	 */
 	if ((rc = cxl_register_adapter(adapter)))
-		goto err_put1;
+		goto err_put_dev;
 
 	if ((rc = cxl_sysfs_adapter_add(adapter)))
-		goto err_put1;
+		goto err_del_dev;
 
 	/* release the context lock as the adapter is configured */
 	cxl_adapter_context_unlock(adapter);
 
 	return adapter;
 
-err_put1:
-	device_unregister(&adapter->dev);
+err_del_dev:
+	device_del(&adapter->dev);
+err_put_dev:
+	put_device(&adapter->dev);
 	free = false;
 	cxl_guest_remove_chardev(adapter);
 err1:
-- 
2.25.1

[PATCH 2/2] cxl: fix possible null-ptr-deref in cxl_pci_init_afu|adapter()

[Yang Yingliang]

If device_register() fails in cxl_pci_afu|adapter(), the device
is not added, device_unregister() can not be called in the error
path, otherwise it will cause a null-ptr-deref because of removing
not added device.

As comment of device_register() says, it should use put_device() to give
up the reference in the error path. So split device_unregister() into
device_del() and put_device(), then goes to put dev when register fails.

Fixes: f204e0b8cedd ("cxl: Driver code for powernv PCIe based cards for userspace access")
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
---
 drivers/misc/cxl/pci.c | 20 ++++++++++++--------
 1 file changed, 12 insertions(+), 8 deletions(-)

diff --git a/drivers/misc/cxl/pci.c b/drivers/misc/cxl/pci.c
index 3de0aea62ade..6d495d641c95 100644
--- a/drivers/misc/cxl/pci.c
+++ b/drivers/misc/cxl/pci.c
@@ -1164,10 +1164,10 @@ static int pci_init_afu(struct cxl *adapter, int slice, struct pci_dev *dev)
 	 * if it returns an error!
 	 */
 	if ((rc = cxl_register_afu(afu)))
-		goto err_put1;
+		goto err_put_dev;
 
 	if ((rc = cxl_sysfs_afu_add(afu)))
-		goto err_put1;
+		goto err_del_dev;
 
 	adapter->afu[afu->slice] = afu;
 
@@ -1176,10 +1176,12 @@ static int pci_init_afu(struct cxl *adapter, int slice, struct pci_dev *dev)
 
 	return 0;
 
-err_put1:
+err_del_dev:
+	device_del(&afu->dev);
+err_put_dev:
 	pci_deconfigure_afu(afu);
 	cxl_debugfs_afu_remove(afu);
-	device_unregister(&afu->dev);
+	put_device(&afu->dev);
 	return rc;
 
 err_free_native:
@@ -1667,23 +1669,25 @@ static struct cxl *cxl_pci_init_adapter(struct pci_dev *dev)
 	 * even if it returns an error!
 	 */
 	if ((rc = cxl_register_adapter(adapter)))
-		goto err_put1;
+		goto err_put_dev;
 
 	if ((rc = cxl_sysfs_adapter_add(adapter)))
-		goto err_put1;
+		goto err_del_dev;
 
 	/* Release the context lock as adapter is configured */
 	cxl_adapter_context_unlock(adapter);
 
 	return adapter;
 
-err_put1:
+err_del_dev:
+	device_del(&adapter->dev);
+err_put_dev:
 	/* This should mirror cxl_remove_adapter, except without the
 	 * sysfs parts
 	 */
 	cxl_debugfs_adapter_remove(adapter);
 	cxl_deconfigure_adapter(adapter);
-	device_unregister(&adapter->dev);
+	put_device(&adapter->dev);
 	return ERR_PTR(rc);
 
 err_release:
-- 
2.25.1

Re: [PATCH 1/2] cxl: fix possible null-ptr-deref in cxl_guest_init_afu|adapter()

[Frederic Barrat]

On 11/11/2022 15:54, Yang Yingliang wrote:
> If device_register() fails in cxl_register_afu|adapter(), the device
> is not added, device_unregister() can not be called in the error path,
> otherwise it will cause a null-ptr-deref because of removing not added
> device.
> 
> As comment of device_register() says, it should use put_device() to give
> up the reference in the error path. So split device_unregister() into
> device_del() and put_device(), then goes to put dev when register fails.
> 
> Fixes: 14baf4d9c739 ("cxl: Add guest-specific code")
> Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
> ---


Thanks for fixing it!
At first, I was slightly uneasy about calling device_del() and 
put_device() directly, i.e. it would be better not to worry about what's 
under the hood of device_unregister(). But 1) I don't see how else to 
fix it and 2) more importantly, I looked at the history of 
device_unregister() to see how frequently it changed. I can now rest 
easy :-)

Acked-by: Frederic Barrat <fbarrat@linux.ibm.com>

   Fred



>   drivers/misc/cxl/guest.c | 24 ++++++++++++++----------
>   1 file changed, 14 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/misc/cxl/guest.c b/drivers/misc/cxl/guest.c
> index 375f692ae9d6..fb95a2d5cef4 100644
> --- a/drivers/misc/cxl/guest.c
> +++ b/drivers/misc/cxl/guest.c
> @@ -965,10 +965,10 @@ int cxl_guest_init_afu(struct cxl *adapter, int slice, struct device_node *afu_n
>   	 * if it returns an error!
>   	 */
>   	if ((rc = cxl_register_afu(afu)))
> -		goto err_put1;
> +		goto err_put_dev;
>   
>   	if ((rc = cxl_sysfs_afu_add(afu)))
> -		goto err_put1;
> +		goto err_del_dev;
>   
>   	/*
>   	 * pHyp doesn't expose the programming models supported by the
> @@ -984,7 +984,7 @@ int cxl_guest_init_afu(struct cxl *adapter, int slice, struct device_node *afu_n
>   		afu->modes_supported = CXL_MODE_DIRECTED;
>   
>   	if ((rc = cxl_afu_select_best_mode(afu)))
> -		goto err_put2;
> +		goto err_remove_sysfs;
>   
>   	adapter->afu[afu->slice] = afu;
>   
> @@ -1004,10 +1004,12 @@ int cxl_guest_init_afu(struct cxl *adapter, int slice, struct device_node *afu_n
>   
>   	return 0;
>   
> -err_put2:
> +err_remove_sysfs:
>   	cxl_sysfs_afu_remove(afu);
> -err_put1:
> -	device_unregister(&afu->dev);
> +err_del_dev:
> +	device_del(&afu->dev);
> +err_put_dev:
> +	put_device(&afu->dev);
>   	free = false;
>   	guest_release_serr_irq(afu);
>   err2:
> @@ -1141,18 +1143,20 @@ struct cxl *cxl_guest_init_adapter(struct device_node *np, struct platform_devic
>   	 * even if it returns an error!
>   	 */
>   	if ((rc = cxl_register_adapter(adapter)))
> -		goto err_put1;
> +		goto err_put_dev;
>   
>   	if ((rc = cxl_sysfs_adapter_add(adapter)))
> -		goto err_put1;
> +		goto err_del_dev;
>   
>   	/* release the context lock as the adapter is configured */
>   	cxl_adapter_context_unlock(adapter);
>   
>   	return adapter;
>   
> -err_put1:
> -	device_unregister(&adapter->dev);
> +err_del_dev:
> +	device_del(&adapter->dev);
> +err_put_dev:
> +	put_device(&adapter->dev);
>   	free = false;
>   	cxl_guest_remove_chardev(adapter);
>   err1:

Re: [PATCH 2/2] cxl: fix possible null-ptr-deref in cxl_pci_init_afu|adapter()

[Frederic Barrat]

On 11/11/2022 15:54, Yang Yingliang wrote:
> If device_register() fails in cxl_pci_afu|adapter(), the device
> is not added, device_unregister() can not be called in the error
> path, otherwise it will cause a null-ptr-deref because of removing
> not added device.
> 
> As comment of device_register() says, it should use put_device() to give
> up the reference in the error path. So split device_unregister() into
> device_del() and put_device(), then goes to put dev when register fails.
> 
> Fixes: f204e0b8cedd ("cxl: Driver code for powernv PCIe based cards for userspace access")
> Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
> ---


Acked-by: Frederic Barrat <fbarrat@linux.ibm.com>

   Fred


>   drivers/misc/cxl/pci.c | 20 ++++++++++++--------
>   1 file changed, 12 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/misc/cxl/pci.c b/drivers/misc/cxl/pci.c
> index 3de0aea62ade..6d495d641c95 100644
> --- a/drivers/misc/cxl/pci.c
> +++ b/drivers/misc/cxl/pci.c
> @@ -1164,10 +1164,10 @@ static int pci_init_afu(struct cxl *adapter, int slice, struct pci_dev *dev)
>   	 * if it returns an error!
>   	 */
>   	if ((rc = cxl_register_afu(afu)))
> -		goto err_put1;
> +		goto err_put_dev;
>   
>   	if ((rc = cxl_sysfs_afu_add(afu)))
> -		goto err_put1;
> +		goto err_del_dev;
>   
>   	adapter->afu[afu->slice] = afu;
>   
> @@ -1176,10 +1176,12 @@ static int pci_init_afu(struct cxl *adapter, int slice, struct pci_dev *dev)
>   
>   	return 0;
>   
> -err_put1:
> +err_del_dev:
> +	device_del(&afu->dev);
> +err_put_dev:
>   	pci_deconfigure_afu(afu);
>   	cxl_debugfs_afu_remove(afu);
> -	device_unregister(&afu->dev);
> +	put_device(&afu->dev);
>   	return rc;
>   
>   err_free_native:
> @@ -1667,23 +1669,25 @@ static struct cxl *cxl_pci_init_adapter(struct pci_dev *dev)
>   	 * even if it returns an error!
>   	 */
>   	if ((rc = cxl_register_adapter(adapter)))
> -		goto err_put1;
> +		goto err_put_dev;
>   
>   	if ((rc = cxl_sysfs_adapter_add(adapter)))
> -		goto err_put1;
> +		goto err_del_dev;
>   
>   	/* Release the context lock as adapter is configured */
>   	cxl_adapter_context_unlock(adapter);
>   
>   	return adapter;
>   
> -err_put1:
> +err_del_dev:
> +	device_del(&adapter->dev);
> +err_put_dev:
>   	/* This should mirror cxl_remove_adapter, except without the
>   	 * sysfs parts
>   	 */
>   	cxl_debugfs_adapter_remove(adapter);
>   	cxl_deconfigure_adapter(adapter);
> -	device_unregister(&adapter->dev);
> +	put_device(&adapter->dev);
>   	return ERR_PTR(rc);
>   
>   err_release:

Re: [PATCH 1/2] cxl: fix possible null-ptr-deref in cxl_guest_init_afu|adapter()

[Andrew Donnellan]

On Fri, 2022-11-11 at 22:54 +0800, Yang Yingliang wrote:
> If device_register() fails in cxl_register_afu|adapter(), the device
> is not added, device_unregister() can not be called in the error
> path,
> otherwise it will cause a null-ptr-deref because of removing not
> added
> device.
> 
> As comment of device_register() says, it should use put_device() to
> give
> up the reference in the error path. So split device_unregister() into
> device_del() and put_device(), then goes to put dev when register
> fails.

The comment around device_add() is relevant too:

  Rule of thumb is: if device_add() succeeds, you should call
  device_del() when you want to get rid of it. If device_add() has
  *not* succeeded, use *only* put_device() to drop the reference count.

> 
> Fixes: 14baf4d9c739 ("cxl: Add guest-specific code")
> Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>

Thanks for the fix!

Acked-by: Andrew Donnellan <ajd@linux.ibm.com>

> ---
>  drivers/misc/cxl/guest.c | 24 ++++++++++++++----------
>  1 file changed, 14 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/misc/cxl/guest.c b/drivers/misc/cxl/guest.c
> index 375f692ae9d6..fb95a2d5cef4 100644
> --- a/drivers/misc/cxl/guest.c
> +++ b/drivers/misc/cxl/guest.c
> @@ -965,10 +965,10 @@ int cxl_guest_init_afu(struct cxl *adapter, int
> slice, struct device_node *afu_n
>          * if it returns an error!
>          */
>         if ((rc = cxl_register_afu(afu)))
> -               goto err_put1;
> +               goto err_put_dev;
>  
>         if ((rc = cxl_sysfs_afu_add(afu)))
> -               goto err_put1;
> +               goto err_del_dev;
>  
>         /*
>          * pHyp doesn't expose the programming models supported by
> the
> @@ -984,7 +984,7 @@ int cxl_guest_init_afu(struct cxl *adapter, int
> slice, struct device_node *afu_n
>                 afu->modes_supported = CXL_MODE_DIRECTED;
>  
>         if ((rc = cxl_afu_select_best_mode(afu)))
> -               goto err_put2;
> +               goto err_remove_sysfs;
>  
>         adapter->afu[afu->slice] = afu;
>  
> @@ -1004,10 +1004,12 @@ int cxl_guest_init_afu(struct cxl *adapter,
> int slice, struct device_node *afu_n
>  
>         return 0;
>  
> -err_put2:
> +err_remove_sysfs:
>         cxl_sysfs_afu_remove(afu);
> -err_put1:
> -       device_unregister(&afu->dev);
> +err_del_dev:
> +       device_del(&afu->dev);
> +err_put_dev:
> +       put_device(&afu->dev);
>         free = false;
>         guest_release_serr_irq(afu);
>  err2:
> @@ -1141,18 +1143,20 @@ struct cxl *cxl_guest_init_adapter(struct
> device_node *np, struct platform_devic
>          * even if it returns an error!
>          */
>         if ((rc = cxl_register_adapter(adapter)))
> -               goto err_put1;
> +               goto err_put_dev;
>  
>         if ((rc = cxl_sysfs_adapter_add(adapter)))
> -               goto err_put1;
> +               goto err_del_dev;
>  
>         /* release the context lock as the adapter is configured */
>         cxl_adapter_context_unlock(adapter);
>  
>         return adapter;
>  
> -err_put1:
> -       device_unregister(&adapter->dev);
> +err_del_dev:
> +       device_del(&adapter->dev);
> +err_put_dev:
> +       put_device(&adapter->dev);
>         free = false;
>         cxl_guest_remove_chardev(adapter);
>  err1:

-- 
Andrew Donnellan    OzLabs, ADL Canberra
ajd@linux.ibm.com   IBM Australia Limited

Re: [PATCH 2/2] cxl: fix possible null-ptr-deref in cxl_pci_init_afu|adapter()

[Andrew Donnellan]

On Fri, 2022-11-11 at 22:54 +0800, Yang Yingliang wrote:
> If device_register() fails in cxl_pci_afu|adapter(), the device
> is not added, device_unregister() can not be called in the error
> path, otherwise it will cause a null-ptr-deref because of removing
> not added device.
> 
> As comment of device_register() says, it should use put_device() to
> give
> up the reference in the error path. So split device_unregister() into
> device_del() and put_device(), then goes to put dev when register
> fails.
> 
> Fixes: f204e0b8cedd ("cxl: Driver code for powernv PCIe based cards
> for userspace access")
> Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>

See reply to patch #1.

This patch puts a few things between the device_del() call and the
put_device() call, but that looks fine - we don't touch afu->dev in the
middle.

Thanks for the fix!

Acked-by: Andrew Donnellan <ajd@linux.ibm.com>

> ---
>  drivers/misc/cxl/pci.c | 20 ++++++++++++--------
>  1 file changed, 12 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/misc/cxl/pci.c b/drivers/misc/cxl/pci.c
> index 3de0aea62ade..6d495d641c95 100644
> --- a/drivers/misc/cxl/pci.c
> +++ b/drivers/misc/cxl/pci.c
> @@ -1164,10 +1164,10 @@ static int pci_init_afu(struct cxl *adapter,
> int slice, struct pci_dev *dev)
>          * if it returns an error!
>          */
>         if ((rc = cxl_register_afu(afu)))
> -               goto err_put1;
> +               goto err_put_dev;
>  
>         if ((rc = cxl_sysfs_afu_add(afu)))
> -               goto err_put1;
> +               goto err_del_dev;
>  
>         adapter->afu[afu->slice] = afu;
>  
> @@ -1176,10 +1176,12 @@ static int pci_init_afu(struct cxl *adapter,
> int slice, struct pci_dev *dev)
>  
>         return 0;
>  
> -err_put1:
> +err_del_dev:
> +       device_del(&afu->dev);
> +err_put_dev:
>         pci_deconfigure_afu(afu);
>         cxl_debugfs_afu_remove(afu);
> -       device_unregister(&afu->dev);
> +       put_device(&afu->dev);
>         return rc;
>  
>  err_free_native:
> @@ -1667,23 +1669,25 @@ static struct cxl
> *cxl_pci_init_adapter(struct pci_dev *dev)
>          * even if it returns an error!
>          */
>         if ((rc = cxl_register_adapter(adapter)))
> -               goto err_put1;
> +               goto err_put_dev;
>  
>         if ((rc = cxl_sysfs_adapter_add(adapter)))
> -               goto err_put1;
> +               goto err_del_dev;
>  
>         /* Release the context lock as adapter is configured */
>         cxl_adapter_context_unlock(adapter);
>  
>         return adapter;
>  
> -err_put1:
> +err_del_dev:
> +       device_del(&adapter->dev);
> +err_put_dev:
>         /* This should mirror cxl_remove_adapter, except without the
>          * sysfs parts
>          */
>         cxl_debugfs_adapter_remove(adapter);
>         cxl_deconfigure_adapter(adapter);
> -       device_unregister(&adapter->dev);
> +       put_device(&adapter->dev);
>         return ERR_PTR(rc);
>  
>  err_release:

-- 
Andrew Donnellan    OzLabs, ADL Canberra
ajd@linux.ibm.com   IBM Australia Limited

Re: [PATCH 1/2] cxl: fix possible null-ptr-deref in cxl_guest_init_afu|adapter()

[Michael Ellerman]

On Fri, 11 Nov 2022 22:54:39 +0800, Yang Yingliang wrote:
> If device_register() fails in cxl_register_afu|adapter(), the device
> is not added, device_unregister() can not be called in the error path,
> otherwise it will cause a null-ptr-deref because of removing not added
> device.
> 
> As comment of device_register() says, it should use put_device() to give
> up the reference in the error path. So split device_unregister() into
> device_del() and put_device(), then goes to put dev when register fails.
> 
> [...]

Applied to powerpc/next.

[1/2] cxl: fix possible null-ptr-deref in cxl_guest_init_afu|adapter()
      https://git.kernel.org/powerpc/c/f949ccee1dde970bc77dc871b4f0b5e651577344
[2/2] cxl: fix possible null-ptr-deref in cxl_pci_init_afu|adapter()
      https://git.kernel.org/powerpc/c/8bf03f557d6c6e108cf47bea32f4a68e276e1157

cheers