[PATCH v2] driver: uio: fix possible memory leak and use-after-free in __uio_register_device

[PATCH v2] driver: uio: fix possible memory leak and use-after-free in __uio_register_device

[liujian]

'idev' is malloced in __uio_register_device() and leak free it before
leaving from the uio_get_minor() error handing case, it will cause
memory leak.

Also, in uio_dev_add_attributes() error handing case, idev is used after
device_unregister(), in which 'idev' has been released, touch idev cause
use-after-free.

Fixes: a93e7b331568 ("uio: Prevent device destruction while fds are open")
Fixes: e6789cd3dfb5 ("uio: Simplify uio error path by using devres
functions")
Signed-off-by: liujian <liujian56@huawei.com>
---
v1->v2:
change git log and fix code

 drivers/uio/uio.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/drivers/uio/uio.c b/drivers/uio/uio.c
index 1313422..be2a943 100644
--- a/drivers/uio/uio.c
+++ b/drivers/uio/uio.c
@@ -940,9 +940,12 @@ int __uio_register_device(struct module *owner,
 	atomic_set(&idev->event, 0);
 
 	ret = uio_get_minor(idev);
-	if (ret)
+	if (ret) {
+		kfree(idev);
 		return ret;
+	}
 
+	device_initialize(&idev->dev);
 	idev->dev.devt = MKDEV(uio_major, idev->minor);
 	idev->dev.class = &uio_class;
 	idev->dev.parent = parent;
@@ -953,7 +956,7 @@ int __uio_register_device(struct module *owner,
 	if (ret)
 		goto err_device_create;
 
-	ret = device_register(&idev->dev);
+	ret = device_add(&idev->dev);
 	if (ret)
 		goto err_device_create;
 
@@ -985,9 +988,10 @@ int __uio_register_device(struct module *owner,
 err_request_irq:
 	uio_dev_del_attributes(idev);
 err_uio_dev_add_attributes:
-	device_unregister(&idev->dev);
+	device_del(&idev->dev);
 err_device_create:
 	uio_free_minor(idev);
+	put_device(&idev->dev);
 	return ret;
 }
 EXPORT_SYMBOL_GPL(__uio_register_device);
-- 
2.7.4

Re: [PATCH v2] driver: uio: fix possible memory leak and use-after-free in __uio_register_device

[Hamish Martin]

On Fri, 2019-01-04 at 22:19 +0800, liujian wrote:
> 'idev' is malloced in __uio_register_device() and leak free it before
> leaving from the uio_get_minor() error handing case, it will cause
> memory leak.
> 
> Also, in uio_dev_add_attributes() error handing case, idev is used
> after
> device_unregister(), in which 'idev' has been released, touch idev
> cause
> use-after-free.
> 
> Fixes: a93e7b331568 ("uio: Prevent device destruction while fds are
> open")
> Fixes: e6789cd3dfb5 ("uio: Simplify uio error path by using devres
> functions")
> Signed-off-by: liujian <liujian56@huawei.com>
> ---
> v1->v2:
> change git log and fix code
> 
>  drivers/uio/uio.c | 10 +++++++---
>  1 file changed, 7 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/uio/uio.c b/drivers/uio/uio.c
> index 1313422..be2a943 100644
> --- a/drivers/uio/uio.c
> +++ b/drivers/uio/uio.c
> @@ -940,9 +940,12 @@ int __uio_register_device(struct module *owner,
>  	atomic_set(&idev->event, 0);
>  
>  	ret = uio_get_minor(idev);
> -	if (ret)
> +	if (ret) {
> +		kfree(idev);
>  		return ret;
> +	}
>  
> +	device_initialize(&idev->dev);
>  	idev->dev.devt = MKDEV(uio_major, idev->minor);
>  	idev->dev.class = &uio_class;
>  	idev->dev.parent = parent;
> @@ -953,7 +956,7 @@ int __uio_register_device(struct module *owner,
>  	if (ret)
>  		goto err_device_create;
>  
> -	ret = device_register(&idev->dev);
> +	ret = device_add(&idev->dev);
>  	if (ret)
>  		goto err_device_create;
>  
> @@ -985,9 +988,10 @@ int __uio_register_device(struct module *owner,
>  err_request_irq:
>  	uio_dev_del_attributes(idev);
>  err_uio_dev_add_attributes:
> -	device_unregister(&idev->dev);
> +	device_del(&idev->dev);
>  err_device_create:
>  	uio_free_minor(idev);
> +	put_device(&idev->dev);
>  	return ret;
>  }
>  EXPORT_SYMBOL_GPL(__uio_register_device);

Looks good to me. Thanks for dealing with those issues.
Reviewed-by: Hamish Martin <hamish.martin@alliedtelesis.co.nz>

Re: [PATCH v2] driver: uio: fix possible memory leak and use-after-free in __uio_register_device

[Greg KH]

On Fri, Jan 04, 2019 at 10:19:08PM +0800, liujian wrote:
> 'idev' is malloced in __uio_register_device() and leak free it before
> leaving from the uio_get_minor() error handing case, it will cause
> memory leak.
> 
> Also, in uio_dev_add_attributes() error handing case, idev is used after
> device_unregister(), in which 'idev' has been released, touch idev cause
> use-after-free.
> 
> Fixes: a93e7b331568 ("uio: Prevent device destruction while fds are open")
> Fixes: e6789cd3dfb5 ("uio: Simplify uio error path by using devres functions")
> Signed-off-by: liujian <liujian56@huawei.com>
> Reviewed-by: Hamish Martin <hamish.martin@alliedtelesis.co.nz>
> ---
> v1->v2:
> change git log and fix code
> 
>  drivers/uio/uio.c | 10 +++++++---
>  1 file changed, 7 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/uio/uio.c b/drivers/uio/uio.c
> index 1313422..be2a943 100644
> --- a/drivers/uio/uio.c
> +++ b/drivers/uio/uio.c
> @@ -940,9 +940,12 @@ int __uio_register_device(struct module *owner,
>  	atomic_set(&idev->event, 0);
>  
>  	ret = uio_get_minor(idev);
> -	if (ret)
> +	if (ret) {
> +		kfree(idev);
>  		return ret;
> +	}
>  
> +	device_initialize(&idev->dev);
>  	idev->dev.devt = MKDEV(uio_major, idev->minor);
>  	idev->dev.class = &uio_class;
>  	idev->dev.parent = parent;
> @@ -953,7 +956,7 @@ int __uio_register_device(struct module *owner,
>  	if (ret)
>  		goto err_device_create;
>  
> -	ret = device_register(&idev->dev);
> +	ret = device_add(&idev->dev);
>  	if (ret)
>  		goto err_device_create;
>  
> @@ -985,9 +988,10 @@ int __uio_register_device(struct module *owner,
>  err_request_irq:
>  	uio_dev_del_attributes(idev);
>  err_uio_dev_add_attributes:
> -	device_unregister(&idev->dev);
> +	device_del(&idev->dev);
>  err_device_create:
>  	uio_free_minor(idev);
> +	put_device(&idev->dev);

device_del() and then put_device()?  I don't think that's a correct
error cleanup path do you?

Please fix one thing at a time here also, this should be a a patch
series, right?

thanks,

greg k-h

RE: [PATCH v2] driver: uio: fix possible memory leak and use-after-free in __uio_register_device

[liujian (CE)]

> -----Original Message-----
> From: Greg KH [mailto:gregkh@linuxfoundation.org]
> Sent: Tuesday, January 08, 2019 12:13 AM
> To: liujian (CE) <liujian56@huawei.com>
> Cc: michal.simek@xilinx.com; hamish.martin@alliedtelesis.co.nz;
> linux-kernel@vger.kernel.org
> Subject: Re: [PATCH v2] driver: uio: fix possible memory leak and use-after-free
> in __uio_register_device
> 
> On Fri, Jan 04, 2019 at 10:19:08PM +0800, liujian wrote:
> > 'idev' is malloced in __uio_register_device() and leak free it before
> > leaving from the uio_get_minor() error handing case, it will cause
> > memory leak.
> >
> > Also, in uio_dev_add_attributes() error handing case, idev is used
> > after device_unregister(), in which 'idev' has been released, touch
> > idev cause use-after-free.
> >
> > Fixes: a93e7b331568 ("uio: Prevent device destruction while fds are
> > open")
> > Fixes: e6789cd3dfb5 ("uio: Simplify uio error path by using devres
> > functions")
> > Signed-off-by: liujian <liujian56@huawei.com>
> > Reviewed-by: Hamish Martin <hamish.martin@alliedtelesis.co.nz>
> > ---
> > v1->v2:
> > change git log and fix code
> >
> >  drivers/uio/uio.c | 10 +++++++---
> >  1 file changed, 7 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/uio/uio.c b/drivers/uio/uio.c index
> > 1313422..be2a943 100644
> > --- a/drivers/uio/uio.c
> > +++ b/drivers/uio/uio.c
> > @@ -940,9 +940,12 @@ int __uio_register_device(struct module *owner,
> >  	atomic_set(&idev->event, 0);
> >
> >  	ret = uio_get_minor(idev);
> > -	if (ret)
> > +	if (ret) {
> > +		kfree(idev);
> >  		return ret;
> > +	}
> >
> > +	device_initialize(&idev->dev);
> >  	idev->dev.devt = MKDEV(uio_major, idev->minor);
> >  	idev->dev.class = &uio_class;
> >  	idev->dev.parent = parent;
> > @@ -953,7 +956,7 @@ int __uio_register_device(struct module *owner,
> >  	if (ret)
> >  		goto err_device_create;
> >
> > -	ret = device_register(&idev->dev);
> > +	ret = device_add(&idev->dev);
> >  	if (ret)
> >  		goto err_device_create;
> >
> > @@ -985,9 +988,10 @@ int __uio_register_device(struct module *owner,
> >  err_request_irq:
> >  	uio_dev_del_attributes(idev);
> >  err_uio_dev_add_attributes:
> > -	device_unregister(&idev->dev);
> > +	device_del(&idev->dev);
> >  err_device_create:
> >  	uio_free_minor(idev);
> > +	put_device(&idev->dev);
> 
> device_del() and then put_device()?  I don't think that's a correct error
> cleanup path do you?
> 
In err_uio_dev_add_attributes error handling case, device_unregister()  will call put_device(), and idev will be released in put_device()
Then in err_device_create error handling case,  uio_free_minor() will trigger use-after-free

Now, divide device_register() into device_initialize() and device_add(), and divide device_unregister() into device_del() and put_device(). 
Call uio_free_minor() and then call put_device() to avoid use-after-free

> Please fix one thing at a time here also, this should be a a patch series, right?
> 
Yes, I will do, thanks~

Best Regards,
Liujian

> thanks,
> 
> greg k-h