linux-ext4 - Re: fuzz testing an ext4fs file system under a 32 bit Linux user mode linux guest let task jbd2/ubda hang

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Message-ID: <20140803184210.GV24826@thunk.org>
Date:	Sun, 3 Aug 2014 14:42:10 -0400
From:	Theodore Ts'o <tytso@....edu>
To:	Toralf Förster <toralf.foerster@....de>
Cc:	linux-ext4@...r.kernel.org,
	UML devel <user-mode-linux-devel@...ts.sourceforge.net>
Subject: Re: fuzz testing an ext4fs file system under a 32 bit Linux user
 mode linux guest let task jbd2/ubda hang

On Sun, Aug 03, 2014 at 03:52:18PM +0200, Toralf Förster wrote:
> Hello,
> 
> fuzzying a 32 bit stable Gentoo x86 linux with trinity (and without excluding the munmap syscall but it might be independed from this) gives within a 32 bit user mode linux guest :

The problem with these sorts of trinity bug reports is that we have no
idea which syscall or set of syscalls might have corrupted kernel
state to the point where the kernel started malfunctioning.

Sometimes, a trinity induced bug is obvious, when it causes a system
call to immediately access an illegal memory location.  But if it
causes some more subtle corruption, possibly in a completely unrelated
subsystem, figuring out what actually happened can be close to
impossible.

So there's not much I can do with this sort of bug report.  If you can
easily repeat it, and you can dump out the system call stream, we
might be able to make a smaller reproduction case, at which point
trying to debug this sort of failure would be tractable.

Cheers,

						- Ted
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