Messages in this thread | | | Date | Mon, 26 Oct 2020 11:05:26 +0200 | From | Mike Rapoport <> | Subject | Re: [PATCH 0/4] arch, mm: improve robustness of direct map manipulation |
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On Mon, Oct 26, 2020 at 01:13:52AM +0000, Edgecombe, Rick P wrote: > On Sun, 2020-10-25 at 12:15 +0200, Mike Rapoport wrote: > > Indeed, for architectures that define CONFIG_ARCH_HAS_SET_DIRECT_MAP > > it is > > possible that __kernel_map_pages() would fail, but since this > > function is > > void, the failure will go unnoticed. > > Could you elaborate on how this could happen? Do you mean during > runtime today or if something new was introduced?
A failure in__kernel_map_pages() may happen today. For instance, on x86 if the kernel is built with DEBUG_PAGEALLOC.
__kernel_map_pages(page, 1, 0);
will need to split, say, 2M page and during the split an allocation of page table could fail.
Currently, the only user of __kernel_map_pages() outside DEBUG_PAGEALLOC is hibernation, but I think it would be safer to entirely prevent usage of __kernel_map_pages() when DEBUG_PAGEALLOC=n.
-- Sincerely yours, Mike.
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