From: "Toralf Förster" <toralf.foerster@gmx.de>
To: Theodore Ts'o <tytso@mit.edu>
Cc: linux-ext4@vger.kernel.org,
UML devel <user-mode-linux-devel@lists.sourceforge.net>
Subject: Re: [uml-devel] fuzz testing an ext4fs file system under a 32 bit Linux user mode linux guest let task jbd2/ubda hang
Date: Sat, 09 Aug 2014 20:45:43 +0200 [thread overview]
Message-ID: <53E66C57.8010303@gmx.de> (raw)
In-Reply-To: <20140803184210.GV24826@thunk.org>
On 08/03/2014 08:42 PM, Theodore Ts'o wrote:
> 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
>
ok, fair enough.
BTW may I just ask, if the following (same 32 bit system, host and UML guest are both at v3.16, 4 trinity childs hammering victims files in a ramdisk within the uML guest) matches the above too ? Or does the BUG output here more helpful data ? :
Kernel panic - not syncing: BUG!
CPU: 0 PID: 105 Comm: kworker/u2:2 Not tainted 3.16.0 #2
Workqueue: writeback bdi_writeback_workfn (flush-98:0)
Stack:
085be12e 085be12e 00000003 086e8547 0000000c 000002b3 85177cc4 85177c74
085015c3 00000000 85177c48 85177c9c 084fd6dd 085c9dc0 08727180 085bae4a
85177ca8 00000000 0000000c 000002b3 85177cc4 85177d10 0818ec0f 085bae4a
Call Trace:
[<085015c3>] dump_stack+0x26/0x28
[<084fd6dd>] panic+0x8f/0x1a9
[<0818ec0f>] mpage_release_unused_pages+0x11f/0x1b0
[<0819395a>] ext4_writepages+0x42a/0x640
[<080d87e5>] do_writepages+0x25/0x50
[<0812fd2c>] __writeback_single_inode+0x3c/0xf0
[<08130064>] writeback_sb_inodes+0x1d4/0x320
[<08130214>] __writeback_inodes_wb+0x64/0xa0
[<08130501>] wb_writeback+0xf1/0x190
[<081308a2>] bdi_writeback_workfn+0xa2/0x2d0
[<08504c56>] ? _raw_spin_unlock_irq+0x16/0x20
[<0809e30c>] ? finish_task_switch.constprop.52+0x3c/0x90
[<08091474>] process_one_work+0x184/0x2f0
[<080918da>] worker_thread+0x2fa/0x540
[<08504c3c>] ? _raw_spin_unlock_irqrestore+0x1c/0x20
[<08502d65>] ? schedule+0x55/0x60
[<080915e0>] ? worker_thread+0x0/0x540
[<080971b6>] kthread+0xd6/0xe0
[<0805f68b>] new_thread_handler+0x6b/0x90
--
Toralf
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next prev parent reply other threads:[~2014-08-09 18:45 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-08-03 13:52 [uml-devel] fuzz testing an ext4fs file system under a 32 bit Linux user mode linux guest let task jbd2/ubda hang Toralf Förster
2014-08-03 18:42 ` Theodore Ts'o
2014-08-09 18:45 ` Toralf Förster [this message]
2014-08-09 20:00 ` Theodore Ts'o
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