linux-kernel - Re: [RFC][PATCH 0/2] x86/boot/KASLR: Restrict kernel to be randomized in mirror regions if existed

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Date:   Thu, 22 Jun 2017 11:36:24 +0800
From:   Chao Fan <fanc.fnst@...fujitsu.com>
To:     Baoquan He <bhe@...hat.com>
CC:     <linux-kernel@...r.kernel.org>, <keescook@...omium.org>,
        <x86@...nel.org>, <caoj.fnst@...fujitsu.com>,
        <douly.fnst@...fujitsu.com>
Subject: Re: [RFC][PATCH 0/2] x86/boot/KASLR: Restrict kernel to be
 randomized in mirror regions if existed

On Thu, Jun 22, 2017 at 11:20:32AM +0800, Baoquan He wrote:
>On 06/22/17 at 11:10am, Chao Fan wrote:
>> Hi all,
>> 
>> After testing this issue for 100 times in total, I think this patchset
>> works well.
>
>Thanks for your effort, Chao!

No problem, and many thanks for your patch, Bao!

>
>Then I will repost with some modification according to the kbuild test report
>and your comment, and thanks again for that. Maybe next week, there is 
>urgent rhel bug now I am trying to fix.

That's OK if next week. But of course, the earlier to repost, the
better for us.
Thank you again for the patch.

Thanks,
Chao Fan

>
>Thanks
>Baoquan
>
>> 
>> The size of physical memory in my test machine is 229G, the size of
>> mirror region is 26G. In the 100 times, 50 times are with this patchset,
>> 50 times are without it.
>> 
>> Here is my test result:
>> 
>> ------------------------------------------------
>>             |total times|in non-mirror|in mirror
>> ------------|-----------|-------------|---------
>> before patch|     50    |      41     |   9
>> ------------|-----------|-------------|---------
>> with patch  |     50    |       0     |  50
>> ------------------------------------------------
>> 
>> Firstly, I add the earlyprintk to get efi map when walking the efi map.
>> Then get the range of mirror regions.
>> In kaslr.c, add the earlyprintk to get random_addr in function
>> choose_random_location, find_random_phys_addr. Then check if the address
>> in which is choosen to extract kernel is in mirror region.
>> 
>> If there are any problems, please let me know.
>> 
>> Thanks,
>> Chao Fan
>> 
>> On Thu, Jun 15, 2017 at 03:52:47PM +0800, Baoquan He wrote:
>> >Our customer reported that Kernel text may be located on non-mirror
>> >region (movable zone) when both address range mirroring feature and
>> >KASLR are enabled.
>> >
>> >The functions of address range mirroring feature are as follows.
>> >- The physical memory region whose descriptors in EFI memory map have
>> >  EFI_MEMORY_MORE_RELIABLE attribute (bit: 16) are mirrored
>> >- The function arranges such mirror region into normal zone and other region
>> >  into movable zone in order to locate kernel code and data on mirror region
>> >
>> >So we need restrict kernel to be located inside mirror region if it
>> >is existed.
>> >
>> >The method is very simple. If efi is enabled, just iterate all efi
>> >memory map and pick up mirror region to process for adding candidate
>> >of slot. If efi disabled or no mirror region existed, still process
>> >e820 memory map. This won't bring much efficiency loss, at worst we
>> >just go through all efi memory maps and found no mirror.
>> >
>> >One question:
>> >From code, though mirror regions are existed, they are meaningful only
>> >if kernelcore=mirror kernel option is specified. Not sure if my understanding
>> >is correct.
>> >
>> >NOTE:
>> >I haven't got a machine with efi mirror region enabled, so only test the
>> >e820 map processing case and the case of no mirror region on efi machine.
>> >So set this as a RFC patchset, will post formal one after above question
>> >is made clear and mirror issue test passed.
>> >
>> >Baoquan He (2):
>> >  x86/boot/KASLR: Adapt process_e820_entry for all kinds of memory map
>> >  x86/boot/KASLR: Restrict kernel to be randomized in mirror regions if
>> >    existed
>> >
>> > arch/x86/boot/compressed/kaslr.c | 129 +++++++++++++++++++++++++++++++--------
>> > 1 file changed, 104 insertions(+), 25 deletions(-)
>> >
>> >-- 
>> >2.5.5
>> >
>> >
>> >
>> 
>> 
>
>