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

[Schspa Shi]

Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> 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@xxxxxxxxx>
>
> 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@xxxxxxxxx/

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