Ext2Fsd Project

Open source ext3/4 file system driver for Windows (2K/XP/WIN7/WIN8)

Bug found in Ext2Fsd 0.60

with 22 comments

Dear all,

We just found a bug in Ext2Fsd 0.60 during code inspection: For extent-based files
that have unwritten extents, writing attempts might cause silent data corruption of
other files or the whole file system. Thought the possibility of data corruption is very
small, to keep your data safe, better not writing any data to EXT4 volumes.

We’ve removed Ext2Fsd 0.60 packages from SourceForge. Right now we are working
on resolving this issue. Likely we will release version 0.61 this weekend.

Matt Wu

Written by Matt

June 4th, 2015 at 10:59 pm

Posted in Ext2Fsd

Tagged with ,

22 Responses to 'Bug found in Ext2Fsd 0.60'

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  1. Did you know what kind of file when write can caused data corruption? like big size, small size, file name contain unicode…?


    6 Jun 15 at 3:45 pm

  2. Files that are generated through fallocate


    6 Jun 15 at 8:24 pm

  3. I install my steam games on ext4 partition. With 0.60 when i verify my game cache, it found all game files faulty. Is this somehow connected to that?


    7 Jun 15 at 9:08 am

  4. No idea… Are you checking your game cache on Windows?


    7 Jun 15 at 9:24 am

  5. You may make checksums for your game cache on Linux, then make another checksums on Windows to see whether there is difference or not. I have no idea whether Steam use fallocate() or not.


    7 Jun 15 at 9:32 am

  6. Yeah i’m checking game cache on windows. I’ll try your suggestion, thanks. Went back to 0.53 and the problem seems to be gone.


    7 Jun 15 at 8:46 pm

  7. The possible reason is: 0.60 doesn’t correctly handle unwritten holes thus the holes will be filled by garbage data in disk.

    0.61 does handle the clearance of garbage holes to make sure data consistency. Give it a try please !


    9 Jun 15 at 1:16 am

  8. Just tried it and same issue.


    9 Jun 15 at 3:51 am

  9. Checksum works though.


    9 Jun 15 at 3:52 am

  10. Maybe because Steam on Windows cannot identify game files downloaded by Steam on Linux?(That makes sence because the executable downloaded by Steam on Linux is ELF but not PE.


    9 Jun 15 at 6:51 am

  11. ok, i can reproduce the same problem there.


    9 Jun 15 at 2:02 pm

  12. And the file checksums are correct.


    9 Jun 15 at 2:04 pm

  13. But they just failed to pass Steam validation


    9 Jun 15 at 2:05 pm

  14. This issue should be fixed in v0.62. Please have a try to verify:

    The root reason of validation failure is: Ext2Fsd direct i/o reports wrong read-length (longer than actual file size), then the checksum programs would do calculation of these extra data, thus it leads to verification failures.


    10 Jun 15 at 1:04 am

  15. Sorry, I was busy couldn’t reply. I just tried 0.62 and problem is gone! Thank you for your hard work 🙂


    10 Jun 15 at 1:21 am

  16. That’s great. Thanks 🙂


    10 Jun 15 at 9:20 am

  17. Hey guys,

    How much longer until Ext2Fsd 0.61 is available?

    Thanks in advance


    7 Jun 15 at 11:55 pm

  18. 0.61 was just released! Not long at all 🙂


    9 Jun 15 at 1:18 am

  19. So was 0.62. Then what about 0.63 ?! Haha


    10 Jun 15 at 9:28 am

  20. Looking forward the new version, since I didn’t get the 0.60 and I use quite a lot Ext4.


    8 Jun 15 at 8:13 pm

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