Re: 4GB+DEBUG_PAGEALLOC oopses with 2.6.0-test3-mm1

[Manfred Spraul <manfred@colorfullife.com>]

Ingo Molnar wrote:

>(in theory it's possible that kernel-internal mounts pass in a pointer
>where pointer + PAGE_SIZE is not a valid kernel address - if this happens
>then we'd get a hard crash.)
>  
>
Exactly that happens.
I'm running with CONFIG_PAGE_DEBUG, i.e. unallocated pages are marked as 
non-present in the linear mapping.

Regarding the i386 trap handler: show_registers tries to hexdump the 
current instructions. It did a __get_user, to avoid causing a fault when 
%eip is invalid.
Now it contains:

>      if ((user_mode(regs) && get_user(c, eip)) ||
>           (!user_mode(regs) && __direct_get_user(c, eip))) {
>              printk(" Bad EIP value.");
>              break;
>      }

I.e. it's already fixed.

--
    Manfred