Re: Re: drivers/s390/char/keyboard.c NULL pointer reference

2017-08-05 Thread Heiko Carstens 
On Sat, Aug 05, 2017 at 09:44:45AM +0800, sohu0106 wrote:
> 
> 
> I don't understand a bit,My idea is 
> 
> in userland
> 
> fd=open("tty3270",O_RDONLY)
> ...
> ret=ioctl(fd,KDGKBDIACR,NULL)
> ...
> 
> then here 
> drivers/s390/char/keyboard.c
> 477 
> case KDGKBDIACR:
>   {
>   struct kbdiacrs __user *a = argp;
>   struct kbdiacr diacr;
>   int i;
>   
>   //a is NULL,a->kb_cnt will crash
>   if (put_user(kbd->accent_table_size, &a->kb_cnt))

a->kb_cnt and &a->kb_cnt is not the same...

Re: drivers/s390/char/keyboard.c NULL pointer reference

2017-08-04 Thread Heiko Carstens 
On Thu, Aug 03, 2017 at 09:57:38PM +0800, sohu0106 wrote:
> 
> 
> Local users able to send the NULL arg argument to kbd_ioctl(), which could 
> cause kernel crash
> 
> 
> 
> 
> diff --git a/keyboard.c 
> b/keyboard.c
> index ba0e4f9..3ec16b1 100644
> --- a/keyboard.c
> +++ b/keyboard.c
> @@ -456,6 +456,8 @@ int kbd_ioctl(struct kbd_data *kbd, unsigned int cmd, 
> unsigned long arg)
>         int perm;
>  
>         argp = (void __user *)arg;
> +       if( !argp )
> +               return -EFAULT;

This doesn't make sense as well. All uaccess functions are able to handle
NULL pointers within user space.