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

sohu0106
2017-08-05T01:44:45Z

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))

At 2017-08-04 17:26:08, "Heiko Carstens" <heiko.carstens@de.ibm.com> wrote:
>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.
>