Mitigation for "Meltdown" on 32-bit (x86_32) is available - please update 'SpectreAndMeltdown' on Ubuntu Wiki.

Registered by daniel CURTIS on 2018-09-26


Linux v4.19 kernel, finally have a Kernel Page-Table Isolation, which means that 'PTI' (previously known as 'KAISER') support for x86_32 architecture is available. 'PTI' provides protection against attack, known as "Meltdown" (CVE-2017-5754), that breaks isolation between user applications and the operating system etc. However, this protection - needed for mitigation - wasn't available on 32-bit x86 systems. Until now.

In my opinion, that is something we really need to be looking at (I mean "Meltdown" mitigation for x86_32 architecture etc.). We should also give attention to the "SpectreAndMeltdown" wiki page and especially "Current Status" section. This chapter is a cause of particular anxiety, and it should be corrected, because contains such an information:

✗ No fix is currently available for Meltdown on 32-bit x86; moving to a 64-bit kernel is the currently recommended mitigation.

However, that's not true anymore. I think, that it could literally, I mean "Current Status" chapter, be changed and updated with a proper informations etc. I would like to help to correct this situation and suggest something. So here are some ideas:

✓ 32-bit x86 finally have Kernel Page-Table Isolation support to mitigate "Meltdown" attack. It is available in Linux v4.19. 'PTI' will be backported to all supported Ubuntu releases.

✓ Fix/mitigation for Meltdown on 32-bit x86 is already available in Linux v4.19 and - in nearly future - will be backported to all Ubuntu supported releases.

These are just my ideas. Honestly, I think, that since 'PTI' is available for x86_32 architecture, "SpectreAndMeltdown" ("Current Status" section) wiki page should be updated quickly, because that site should not mislead Users. It should not longer be possible to deceive them with incorrect statement. That's wrong.

Thanks, best regards.

For more informations about how 'PTI' was implemented, created for 32-bit x86 architecture, I would like to point out - for example - the commit '7757d607c6b31' ("x86/pti: Allow CONFIG_PAGE_TABLE_ISOLATION for x86_32"). There are also two very valuable websites: (PATCH v8.; also v2-v7) (See "Architecture-specific" changes)

If someone would like to read about 'KPTI' and how it evolved, what was the state in the past, details, users comments etc., please check second link above and next click 'kernel page-table isolation' link.

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