In fake_init(), __root_device_register() is possible to fail but it's
ignored, which can cause unregistering vme_root fail when exit.

 general protection fault,
 probably for non-canonical address 0xdffffc000000008c
 KASAN: null-ptr-deref in range [0x0000000000000460-0x0000000000000467]
 RIP: 0010:root_device_unregister+0x26/0x60
 Call Trace:
  <TASK>
  __x64_sys_delete_module+0x34f/0x540
  do_syscall_64+0x38/0x90
  entry_SYSCALL_64_after_hwframe+0x63/0xcd

Return error when __root_device_register() fails.

Fixes: 658bcdae9c67 ("vme: Adding Fake VME driver")
Signed-off-by: Chen Zhongjin <chenzhongjin@huawei.com>
---
 drivers/staging/vme_user/vme_fake.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/staging/vme_user/vme_fake.c b/drivers/staging/vme_user/vme_fake.c
index dd646b0c531d..1ee432c223e2 100644
--- a/drivers/staging/vme_user/vme_fake.c
+++ b/drivers/staging/vme_user/vme_fake.c
@@ -1073,6 +1073,8 @@ static int __init fake_init(void)
 
 	/* We need a fake parent device */
 	vme_root = __root_device_register("vme", THIS_MODULE);
+	if (IS_ERR(vme_root))
+		return PTR_ERR(vme_root);
 
 	/* If we want to support more than one bridge at some point, we need to
 	 * dynamically allocate this so we get one per device.
-- 
2.17.1

On Mon, Dec 05, 2022 at 04:48:05PM +0800, Chen Zhongjin wrote:
> In fake_init(), __root_device_register() is possible to fail but it's
> ignored, which can cause unregistering vme_root fail when exit.
> 
>  general protection fault,
>  probably for non-canonical address 0xdffffc000000008c
>  KASAN: null-ptr-deref in range [0x0000000000000460-0x0000000000000467]
>  RIP: 0010:root_device_unregister+0x26/0x60
>  Call Trace:
>   <TASK>
>   __x64_sys_delete_module+0x34f/0x540
>   do_syscall_64+0x38/0x90
>   entry_SYSCALL_64_after_hwframe+0x63/0xcd
> 
> Return error when __root_device_register() fails.
> 
> Fixes: 658bcdae9c67 ("vme: Adding Fake VME driver")
> Signed-off-by: Chen Zhongjin <chenzhongjin@huawei.com>
> ---
>  drivers/staging/vme_user/vme_fake.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/staging/vme_user/vme_fake.c b/drivers/staging/vme_user/vme_fake.c
> index dd646b0c531d..1ee432c223e2 100644
> --- a/drivers/staging/vme_user/vme_fake.c
> +++ b/drivers/staging/vme_user/vme_fake.c
> @@ -1073,6 +1073,8 @@ static int __init fake_init(void)
>  
>  	/* We need a fake parent device */
>  	vme_root = __root_device_register("vme", THIS_MODULE);

This should be calling root_device_register() as well, not this version
of the call.

thanks,

greg k-h

Hi,

On 2022/12/5 20:31, Greg KH wrote:
> On Mon, Dec 05, 2022 at 04:48:05PM +0800, Chen Zhongjin wrote:
>> In fake_init(), __root_device_register() is possible to fail but it's
>> ignored, which can cause unregistering vme_root fail when exit.
>>
>>   general protection fault,
>>   probably for non-canonical address 0xdffffc000000008c
>>   KASAN: null-ptr-deref in range [0x0000000000000460-0x0000000000000467]
>>   RIP: 0010:root_device_unregister+0x26/0x60
>>   Call Trace:
>>    <TASK>
>>    __x64_sys_delete_module+0x34f/0x540
>>    do_syscall_64+0x38/0x90
>>    entry_SYSCALL_64_after_hwframe+0x63/0xcd
>>
>> Return error when __root_device_register() fails.
>>
>> Fixes: 658bcdae9c67 ("vme: Adding Fake VME driver")
>> Signed-off-by: Chen Zhongjin <chenzhongjin@huawei.com>
>> ---
>>   drivers/staging/vme_user/vme_fake.c | 2 ++
>>   1 file changed, 2 insertions(+)
>>
>> diff --git a/drivers/staging/vme_user/vme_fake.c b/drivers/staging/vme_user/vme_fake.c
>> index dd646b0c531d..1ee432c223e2 100644
>> --- a/drivers/staging/vme_user/vme_fake.c
>> +++ b/drivers/staging/vme_user/vme_fake.c
>> @@ -1073,6 +1073,8 @@ static int __init fake_init(void)
>>   
>>   	/* We need a fake parent device */
>>   	vme_root = __root_device_register("vme", THIS_MODULE);
> This should be calling root_device_register() as well, not this version
> of the call.
Of course it should. Have sent another patch for it.

Thanks for your time!
Chen
> thanks,
>
> greg k-h