[PATCH] driver: base: fix UAF when driver_attach failed

[PATCH] driver: base: fix UAF when driver_attach failed

[Schspa Shi]

When driver_attach(drv); failed, the driver_private will be freed.
But it has been added to the bus, which caused a UAF.

To fix it, we need to delete it from the bus when failed.

Fixes: 190888ac01d0 ("driver core: fix possible missing of device probe")

Signed-off-by: Schspa Shi <schspa@gmail.com>
---
 drivers/base/bus.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/base/bus.c b/drivers/base/bus.c
index 97936ec49bde..7ca47e5b3c1f 100644
--- a/drivers/base/bus.c
+++ b/drivers/base/bus.c
@@ -617,7 +617,7 @@ int bus_add_driver(struct device_driver *drv)
 	if (drv->bus->p->drivers_autoprobe) {
 		error = driver_attach(drv);
 		if (error)
-			goto out_unregister;
+			goto out_del_list;
 	}
 	module_add_driver(drv->owner, drv);
 
@@ -644,6 +644,8 @@ int bus_add_driver(struct device_driver *drv)
 
 	return 0;
 
+out_del_list:
+	klist_del(&priv->knode_bus);
 out_unregister:
 	kobject_put(&priv->kobj);
 	/* drv->p is freed in driver_release()  */
-- 
2.29.0

Re: [PATCH] driver: base: fix UAF when driver_attach failed

[Greg KH]

On Wed, May 11, 2022 at 08:43:36PM +0800, Schspa Shi wrote:
> When driver_attach(drv); failed, the driver_private will be freed.
> But it has been added to the bus, which caused a UAF.
> 
> To fix it, we need to delete it from the bus when failed.
> 
> Fixes: 190888ac01d0 ("driver core: fix possible missing of device probe")
> 
> Signed-off-by: Schspa Shi <schspa@gmail.com>

No blank line needed after fixes:

> ---
>  drivers/base/bus.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/base/bus.c b/drivers/base/bus.c
> index 97936ec49bde..7ca47e5b3c1f 100644
> --- a/drivers/base/bus.c
> +++ b/drivers/base/bus.c
> @@ -617,7 +617,7 @@ int bus_add_driver(struct device_driver *drv)
>  	if (drv->bus->p->drivers_autoprobe) {
>  		error = driver_attach(drv);
>  		if (error)
> -			goto out_unregister;
> +			goto out_del_list;
>  	}
>  	module_add_driver(drv->owner, drv);
>  
> @@ -644,6 +644,8 @@ int bus_add_driver(struct device_driver *drv)
>  
>  	return 0;
>  
> +out_del_list:
> +	klist_del(&priv->knode_bus);

Odd, how did you find this?  Has this ever been triggered by any
real-world situations?

thanks,

greg k-h

Re: [PATCH] driver: base: fix UAF when driver_attach failed

[Schspa Shi]

Greg KH <gregkh@linuxfoundation.org> writes:

> On Wed, May 11, 2022 at 08:43:36PM +0800, Schspa Shi wrote:
>> When driver_attach(drv); failed, the driver_private will be freed.
>> But it has been added to the bus, which caused a UAF.
>>
>> To fix it, we need to delete it from the bus when failed.
>>
>> Fixes: 190888ac01d0 ("driver core: fix possible missing of device probe")
>>
>> Signed-off-by: Schspa Shi <schspa@gmail.com>
>
> No blank line needed after fixes:
>

Do I need a new patch version for this ?

>> ---
>>  drivers/base/bus.c | 4 +++-
>>  1 file changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/base/bus.c b/drivers/base/bus.c
>> index 97936ec49bde..7ca47e5b3c1f 100644
>> --- a/drivers/base/bus.c
>> +++ b/drivers/base/bus.c
>> @@ -617,7 +617,7 @@ int bus_add_driver(struct device_driver *drv)
>>      if (drv->bus->p->drivers_autoprobe) {
>>              error = driver_attach(drv);
>>              if (error)
>> -                    goto out_unregister;
>> +                    goto out_del_list;
>>      }
>>      module_add_driver(drv->owner, drv);
>>
>> @@ -644,6 +644,8 @@ int bus_add_driver(struct device_driver *drv)
>>
>>      return 0;
>>
>> +out_del_list:
>> +    klist_del(&priv->knode_bus);
>
> Odd, how did you find this?  Has this ever been triggered by any
> real-world situations?
>

I found this when fixing this issue via code review.
Link: https://lore.kernel.org/all/20220508150247.38204-1-schspa@gmail.com/

It shouldn't not happen, unless the bus driver's match() return value < 0.
Which never happens with the existing bus drivers.

> thanks,
>
> greg k-h

---
BRs

Schspa Shi