Messages in this thread | | | Date | Wed, 19 Apr 2017 22:55:17 +0800 | From | Baoquan He <> | Subject | Re: KASLR causes intermittent boot failures on some systems |
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On 04/19/17 at 07:27am, Thomas Garnier wrote: > On Wed, Apr 19, 2017 at 6:36 AM, Baoquan He <bhe@redhat.com> wrote: > > Hi all, > > > > I login in Jeff's system, and added debug code, no clue found. However > > DaveY found he disabled page_offset randomization only and the efi issue > > won't be seen on his system with kaslr enabled. I did it too on Jeff's > > pmem system, it has the same result. I have rebooted several times, all > > boot successfully. In the current code, no __PAGE_OFFSET_BASE is used > > directly, don't know why it failed. > > Great! I still cannot repro it. > > > > > Does anyone have any idea or hint I can try? I read pmem code about > > the devm_nsio_enable/pmem_attach_disk/arch_add_memory, have no idea yet. > > I would test couple things: > - Set page_offset_base to 0 by default and set it to > __PAGE_OFFSET_BASE in kernel_randomize_memory (without randomizing > it). If it crashes on a low address, it might be due to using __va or > PAGE_OFFSET in general before randomization is done.
Thanks, Thomas!
Changed code like below, it should have the same effect as you suggested.
@@ -140,6 +140,8 @@ void __init kernel_randomize_memory(void) * Select a random virtual address using the extra entropy * available. */ + if (i == 0) + continue; entropy = remain_entropy / (ARRAY_SIZE(kaslr_regions) - i);
Didn't see failure since above change applied.
> - Does any change in __PAGE_OFFSET lead to a crash? Or only when > __PAGE_OFFSET is on a specific range. Given that you may have to > reboot multiple times to get a crash, I assume that a specific range > is the problem but might be worth checking.
Good point, will check.
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