[Hardy-xen] SRU: Fix OMG how did this ever work (32bit)

[Stefan Bader]

On 21.06.2011 17:55, Stefan Bader wrote:
> SRU Justification:
> 
> Impact: For i386 PGDs are stored in a linked list. For this two elements of
> struct page are (mis-)used. To have a backwards pointer, the private field is
> assigned a pointer to the index field of the previous struct page. The main
> problem there was that list_add and list_del operations accidentally were done
> twice. Which leads to accesses to (after first list operation) innocent struct
> pages.
> 
> Fix: This is a bit more than needed to fix the bug itself, but it will bring our
> code more into a shape that resembles upstream (factually there is only a 2.6.18
> upstream but that code did not do the double list access).
> 
> Testcase: Running a 32bit domU (64bit Hardy dom0, though that should not matter)
> with the xen kernel and doing a lot of process starts (like the aslr qa
> regression test does) would quite soon crash because the destructor of a PTE
> (which incidentally is stored in index) was suddenly overwritten.
> 
> Patches are attached directly. Those would go into the patches directory.
> 
> Note, that I attributed it to fix bug 705562 which has not yet been verified.
> But the way of failure was just exactly the same.
> 
> -Stefan
> 
Darn, git send-email did not work as expected here. One may guess but 2,3 and 4
are the 3 individual patches, while 1 is the one against the hardy tree.

-Stefan