Root FS corruption

[Thomas-Martin Seck]

* Yar Tikhiy <yar at comp.chem.msu.su>:

> I saw the following / corruption in a fresh CURRENT when using
> nextboot.  Of course, it wasn't the fault of nextboot itself,
> nextboot simply was the only utility to modify / in my case.
> 
> I found the contents of nextboot.conf once in my custom /root/supfile,
> the other time in the stock /etc/protocols.  /etc/protocols was
> large enough to see how the corruption had happened: the first
> fragment, 2048 bytes, of the file was replaced by the contents of
> nextboot.conf, zero padded.
>
> The / was a usual 2048/16384 UFS2 without soft-updates.  The kernel
> was GENERIC.  Forced fsck reported no problems at all.  The / had
> never been dirty because I used nextboot to boot single-user with
> all FSen read-only and investigate a panic unrelated to FS.
> 
> Did any one see a similar problem of fragment mis-allocation?

I experienced the exact same corruption some months ago with a RELENG_6
test system I update regularly. Unfortunately, this corruption happened
only once, I was never able to reproduce it since.

The kernel is a stripped down GENERIC, /root is a 2048/16384 UFS2 fs.