Re: [PATCH] vsprintf: Do not break early boot with probing addresses

Martin Schwidefsky
2019-05-10T16:32:58Z

On Fri, 10 May 2019 12:24:01 -0400
Steven Rostedt <rostedt@goodmis.org> wrote:

> On Fri, 10 May 2019 10:42:13 +0200
> Petr Mladek <pmladek@suse.com> wrote:
>
> > static const char *check_pointer_msg(const void *ptr)
> > {
> > - char byte;
> > -
> > if (!ptr)
> > return "(null)";
> >
> > - if (probe_kernel_address(ptr, byte))
> > + if ((unsigned long)ptr < PAGE_SIZE || IS_ERR_VALUE(ptr))
> > return "(efault)";
> >
>
>
> < PAGE_SIZE ?
>
> do you mean: < TASK_SIZE ?

The check with < TASK_SIZE would break on s390. The 'ptr' is
in the kernel address space, *not* in the user address space.
Remember s390 has two separate address spaces for kernel/user
the check < TASK_SIZE only makes sense with a __user pointer.

--
blue skies,
Martin.

"Reality continues to ruin my life." - Calvin.