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

[Petr Mladek]

On Fri 2019-05-10 10:42:13, Petr Mladek wrote:
> The commit 3e5903eb9cff70730 ("vsprintf: Prevent crash when dereferencing
> invalid pointers") broke boot on several architectures. The common
> pattern is that probe_kernel_read() is not working during early
> boot because userspace access framework is not ready.
> 
> It is a generic problem. We have to avoid any complex external
> functions in vsprintf() code, especially in the common path.
> They might break printk() easily and are hard to debug.
> 
> Replace probe_kernel_read() with some simple checks for obvious
> problems.

JFYI, I have sent a pull request with this patch, see
https://lkml.kernel.org/r/20190510144718.riyy72g4cy5nkggx@pathway.suse.cz

Best Regards,
Petr