Messages in this thread | | | Date | Mon, 10 Sep 2018 08:18:39 +0200 | From | Ingo Molnar <> | Subject | Re: [PATCH v2 1/3] x86/mm/KASLR: Fix the wrong calculation of kalsr region initial size |
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* Baoquan He <bhe@redhat.com> wrote:
> In memory KASLR, __PHYSICAL_MASK_SHIFT is taken to calculate the > initial size of the direct mapping region. This is right in the > old code where __PHYSICAL_MASK_SHIFT was equal to MAX_PHYSMEM_BITS, > 46bit, and only 4-level mode was supported. > > Later, in commit: > b83ce5ee91471d ("x86/mm/64: Make __PHYSICAL_MASK_SHIFT always 52"), > __PHYSICAL_MASK_SHIFT was changed to be 52 always, no matter it's > 5-level or 4-level. This is wrong for 4-level paging. Then when > adapt phyiscal memory region size based on available memory, it > will overflow if the amount of system RAM and the padding is bigger > than 64TB. > > In fact, here MAX_PHYSMEM_BITS should be used instead. Fix it by > replacing __PHYSICAL_MASK_SHIFT with MAX_PHYSMEM_BITS. > > Fixes: b83ce5ee9147 ("x86/mm/64: Make __PHYSICAL_MASK_SHIFT always 52") > Signed-off-by: Baoquan He <bhe@redhat.com> > Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> > Reviewed-by: Thomas Garnier <thgarnie@google.com>
So this changelog has a handful of problems:
- there's a typo in the title
- what does 'memory KASLR' mean? All KASLR deals with memory.
- there's a typo in the second paragraph
- Please punctuate more precisely: '64TB' is written as '64 TB' and '46bit' is written as '46 bits'
- '52 always' is accurate but '52 bits always' would be more useful: write out units where appropriate to reduce ambiguity and parsing complexity of changelogs. Also, in this particular sentence it should be 'always 52 bits'.
- s/when adapt /when we adapt
- s/This is right in the old code /This is correct in the old code
Thanks,
Ingo
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