APFS Bug in macOS High Sierra Can Cause Data Loss When Writing to Disk Images

Discussion in 'MacRumors.com News Discussion' started by MacRumors, Feb 19, 2018.

  1. MacRumors macrumors bot


    Apr 12, 2001

    Apple's APFS file system included in macOS High Sierra suffers from a disk image vulnerability that in certain circumstances can lead to data loss, according to the creator of Carbon Copy Cloner.

    In a blog post last Thursday, software developer Mike Bombich explained that he had uncovered the data writing flaw in the Apple File System, or APFS, through his regular work with "sparse" disk images.


    For those who aren't familiar with the term, a sparse disk image is basically a file that macOS mounts on the desktop and treats as if it was a physically attached drive with a classic disk volume structure. The flexibility of sparse disk images means they are commonly used in the course of performing backup and disk cloning operations, hence Bombich's extensive experience with them.
    Two related problems are identified by Bombich, above. The first is that the free space on the APFS-formatted sparse disk image doesn't update as it should when the free space on the underlying physical host disk is reduced. The second problem is the lack of error reports when write requests fail to dynamically grow the disk image, resulting in data being "written" into a void. Bombich tracks both bugs back to macOS's background "diskimages-helper" application service, which he has since reported to Apple.

    Bombich's video demonstrating the APFS bug

    Every installation of High Sierra on Macs with all-flash storage converts the existing file system to APFS, which is optimized for modern storage systems like solid-state drives. However, as Bombich notes, ordinary APFS volumes like SSD startup disks are not affected by the problem described above, so the vast majority of users won't be affected by it - the flaw is most applicable when making backups to network volumes. Bombich says Carbon Copy Cloner will not support AFPS-formatted sparse disk images until Apple resolves the issue.

    The APFS flaw follows the discovery of another bug in Apple's operating systems that received extensive coverage last week. That bug is induced by sending a specific character in the Indian language Telugu, which causes certain apps on iPhones, iPads, and Macs to freeze up and become unresponsive. The Telugu character bug has already been fixed in Apple's upcoming iOS 11.3 and macOS 10.13.4 software updates.

    Article Link: APFS Bug in macOS High Sierra Can Cause Data Loss When Writing to Disk Images
  2. kahkityoong macrumors 6502


    Jan 31, 2011
    Melbourne, Australia
    Glad I reverted to Sierra when I deemed High Sierra a S-show after a couple of weeks. There seems to be no end to Apple's incompetence with this OS.
  3. amaze1499 macrumors regular


    Oct 16, 2014
    quote: The bug has already been fixed in Apple's upcoming iOS 11.3 and macOS 10.13.4 software updates.
  4. BaltimoreMediaBlog macrumors 6502a


    Jul 30, 2015
    DC / Baltimore / Northeast
    Wow, this makes me wonder. Did Apple and APFS destroy my only 2 year old Seagate drive with mostly disk images on it?

    I kept wondering, how could my newest standard HD used the least of all fail quicker then the much older ones? The complete failure boggles my mind. Seagate blamed harsh usage, but it was not the system drive, only contained media and music and disk images for specific purposes.
  5. navaira macrumors 68040


    May 28, 2015
    Amsterdam, Netherlands
    But... Bugs in Apple software never happen! It's probably about Android!
  6. quaresma macrumors member


    Jan 20, 2013
  7. CmdrLaForge macrumors 601


    Feb 26, 2003
    around the world
    Not cool. Data loss is a very serious bug. I hope Apple releases the fix soon.
  8. klunernet macrumors member


    Jul 14, 2011
    Hoorn, NL
    I wonder if this is related to high sierra suddenly invalidating my time machine backups to my NAS, and demanding to do a new full. (Loosing two years worth of history). Then doing it again 2 weeks later.
  9. JessePinkman, Feb 19, 2018
    Last edited: Feb 19, 2018

    JessePinkman Suspended


    Feb 18, 2018
    this happens randomly with steam games on my macbook pro it happened with pillars of eternity was almost crashing my nvidia gpu then i verified game files via steam client and it found few mb corrupted data for no reason (no power loss or resets) shh macos bugs these days...
  10. Novus John macrumors regular

    Sep 27, 2015
    High Sierra has been a complete disaster for me. My computer locks up for 5-10 seconds every few hours. Probably some memory leaks or something. Either way this is really pathetic, even windows works better than this.
  11. Royksöpp macrumors 6502a


    Nov 4, 2013
    Another day, another bug. How very Apple-esque. #ifstevejobswasalive #firetimcook
  12. dannys1 Suspended


    Sep 19, 2007
    Almost certainly not, your NAS won't be formatted as APFS.
  13. Loge macrumors 68030


    Jun 24, 2004
  14. Royksöpp macrumors 6502a


    Nov 4, 2013
    Apple makes no mistakes. I love the notch, I embrace the notch. I think therefore I am, the notch.
  15. meaning-matters macrumors 6502


    Dec 13, 2013
  16. Lesser Evets macrumors 68040

    Lesser Evets

    Jan 7, 2006
    “Bombich”... you can’t make this stuff up.
  17. fermat-au macrumors 6502

    Dec 7, 2009
    It is bugs such as this, that this what for mission critical task sys admins don't update there system to the newest version for software the day or even week or month it ships.
  18. Kabeyun macrumors 68020


    Mar 27, 2004
    Eastern USA
    I feel your pain. Had a major memory leak after moving to Sierra, let alone High Sierra. Progressively unresponsive about 10 minutes after reboot. Wasn’t the notorious iTunes leak either. Couldn’t trace it. Went back to El Cap and am quite happy. My only complaint is that Photos can’t pick a new key frame from a live photo. I’ll live.
  19. BaggieBoy macrumors 6502


    May 29, 2012
    Same happened to me, 2 new full backups required so far.
  20. Merode macrumors 6502a


    Nov 5, 2013
    Warszawa, Poland
    Making fun of surnames. Feels like primary school already.
  21. tkermit macrumors 68040


    Feb 20, 2004
    No. Time Machine doesn't support backing up to APFS-formatted disk images, so this bug should have no effect on it.
  22. Eagle_Eye macrumors newbie

    Oct 10, 2017
    Anyone else noticed strange behaviour when creating a zip archive? There was a moment (when I was running High Sierra, downgraded to Sierra) where I had to re-zip a folder 6 times before APFS gave me the correct files. In all 5 previous versions the zip contained an older version of a Word file.
  23. dannys1 Suspended


    Sep 19, 2007
    Same, Mike is a really good guy and we use CCC every day in work and it's my businesses number 1 tool for deployment, I prefer it over all other deployment tools that Mac Admins usually use.

    APFS has lot's of bugs - i've discovered two edge use cases. Rsync with Apples new AP controllers (which come in MacBook Pros built this year and iMac Pro's) runs 4x slower than normal (which makes a 10minute copy a 40 minute copy) - also APFS formatted raid drives when used as a boot volume take minutes to appear in the macOS boot menu.

    Both are edge cases that 99% of users will never experience (though the AP controller is a bigger deal and more and more people will come into that as those computers become more available, so it needs sorted with by Apple or the Samba team working on rsync...i've reported it to both)
    --- Post Merged, Feb 19, 2018 ---
    It's his surname?...
  24. JessePinkman Suspended


    Feb 18, 2018
    imo its hardware not software apple have been using cheap memories since tim cook
  25. Luigi55 macrumors newbie

    Oct 1, 2014
    Same problem happens on my MacBook Pro 13" Mid 2014.

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