[DragonFlyBSD - Bug #3237] msdosfs: can't properly read files longer than couple of kilobytes

bugtracker-admin at leaf.dragonflybsd.org bugtracker-admin at leaf.dragonflybsd.org
Fri Jun 5 16:50:01 PDT 2020

Issue #3237 has been updated by piecuch.

> then explain what this means.

> "write on dfly - corrupted data on dfly,"

Apologies for vague messages. This means that data written on dfly appears to be corrupted on dfly. Reading this file from other OS (Linux, FreeBSD) returns correct output.

I tried bisecting the bug but I haven't learned much:

- 5.4.0 - the bug still occurs - this is the oldest vkernel I was able to build without much effort and the only one I ran under vkernel.

The following images were downloaded from dragonflybsd.org and tested without virtualization:
- 5.0.0 - the bug still occurs
- 4.4.0 - the bug still occurs
- 4.0.2 - the bug still occurs

Anything older than that wouldn't boot on my machine so I had to use qemu for testing. I tried 3.6.1, 2.4.1 and 2.6.3 but I couldn't make the OS get to the filesystem because of various reasons (panics, newfs_msdos crashes, the OS won't detect drives) which made me question whether these support qemu.

If you think there's value in trying harder with older releases, I'm happy to do it.

Bug #3237: msdosfs: can't properly read files longer than couple of kilobytes

* Author: piecuch
* Status: New
* Priority: Normal
* Assignee: 
* Category: Other
* Target version: master
Reading a file from msdosfs reports valid data within the first couple of kilobytes, everything after that is only NULL bytes (or it might be some data from a different sector which is currently zeroed).

I have tested this on the following configurations:
write on Linux - corrupted data on dfly, correct data on Linux
write on dfly - corrupted data on dfly, correct data on Linux

I am running latest version from master.

I will see if this bug can be reproduced on freebsd and try to fix that/port stuff from freebsd. Hints welcome.

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