* Re: [uml-devel] Fwd: Re: trinity doesn't exit after its finished
2014-11-20 19:01 ` [uml-devel] Fwd: Re: trinity doesn't exit after its finished Toralf Förster
@ 2014-11-20 19:03 ` Richard Weinberger
0 siblings, 0 replies; 2+ messages in thread
From: Richard Weinberger @ 2014-11-20 19:03 UTC (permalink / raw)
To: Toralf Förster; +Cc: Daniel Walter, UML devel
On Thu, Nov 20, 2014 at 8:01 PM, Toralf Förster <toralf.foerster@gmx.de> wrote:
> A recent question at trinity's mailing list (http://news.gmane.org/gmane.comp.security.fuzzing.trinity) points probably to a hostfs issue - therefore I'd like to forward the answer f Dave Jones here.
>
> ANd /me wonders how to use ftrace to further dig into this issue ?
UML has no ftrace support.
But Daniel is working on it.
>
>
>
> -------- Forwarded Message --------
> Subject: Re: trinity doesn't exit after its finished
> Date: Thu, 20 Nov 2014 13:21:54 -0500
> From: Dave Jones <davej@redhat.com>
> To: Toralf Förster <toralf.foerster@gmx.de>
> CC: trinity@vger.kernel.org
>
> On Thu, Nov 20, 2014 at 07:08:15PM +0100, Toralf Förster wrote:
> > With latest git tree of trinity at a user mode linux image it stays here forever:
> > [child0:5249] <timed out>
> > [main] Bailing main loop because Completed maximum number of operations..
> > [watchdog] [5096] Watchdog exiting because Completed maximum number of operations..
>
> So that [main] line is the last line in main_loop()
> On return, we do this..
>
> 159 main_loop();
> 160
> 161 shm->mainpid = 0;
> 162 _exit(EXIT_SUCCESS);
>
> and yet..
>
> > The proces list shows:
> >
> > $ ps fx -eo pid,start_time,command | grep -e trinity -e sleep | grep -v grep
> > 4878 18:30 | \_ bash -c logger "2#-1, M=/mnt/hostfs"; cd ~; sudo su -c 'if [[ -d ./t3 ]]; then sudo chmod -R a+rwx ./t3; sudo rm -rf ./t3; fi'; mkdir ./t3 && cd ./t3 || exit; if [[ -n /mnt/hostfs ]]; then if [[ -d /mnt/hostfs/victims/v1 ]]; then sudo chmod -R a+rwx /mnt/hostfs/victims/v1; sudo rm -rf /mnt/hostfs/victims/v1 || exit; fi; mkdir -p /mnt/hostfs/victims/v1/v2; for i in $(seq -w 0 99); do touch /mnt/hostfs/victims/v1/v2/f$i; mkdir /mnt/hostfs/victims/v1/v2/d$i; done; fi; MALLOC_CHECK_=2 trinity -C 2 -N 25000 -q -V /mnt/hostfs/victims/v1/v2
> > 5095 18:30 | \_ trinity -C 2 -N 25000 -q -V /mnt/hostfs/victims/v1/v2
> > 5096 18:30 | \_ [trinity-watchdo] <defunct>
> > 5097 18:30 | \_ [trinity-main]
>
> Somehow it's still around.
>
> > Here are the stacks:
> >
> > $ sudo cat /proc/5097/stack
> >
> > [<0805f8b4>] __switch_to+0x44/0x70
> > [<0850b194>] __schedule+0x2f4/0x3a0
> > [<08097b8a>] __cond_resched+0x1a/0x30
> > [<0850b371>] _cond_resched+0x31/0x50
> > [<080dbbb2>] truncate_inode_pages_range+0x192/0x650
> > [<080dc102>] truncate_inode_pages_final+0x52/0x60
> > [<08275f18>] hostfs_evict_inode+0x18/0x40
> > [<08126e8d>] evict+0xdd/0x1b0
> > [<08127b0d>] iput+0x16d/0x180
> > [<08123538>] __dentry_kill+0x138/0x200
> > [<08123f66>] dput+0x156/0x180
> > [<0810fa15>] __fput+0x175/0x190
> > [<0810fa6b>] ____fput+0xb/0x10
> > [<08092956>] task_work_run+0x76/0x90
> > [<0807e92d>] do_exit+0x32d/0x940
> > [<0807f022>] do_group_exit+0xa2/0xf0
> > [<0807f087>] SyS_exit_group+0x17/0x20
> > [<08062980>] handle_syscall+0x60/0x80
> > [<080746fc>] userspace+0x46c/0x5e0
> > [<0805f720>] fork_handler+0x60/0x70
> > [<ffffffff>] 0xffffffff
>
> This is the interesting part. The process is about to exit,
> but hostfs is doing.. something. It might just be taking a really
> long time, or it might be stuck. If it happens again, you might
> be able to use ftrace to figure out if hostfs is actually making
> forward progress or not.
>
> Perhaps the UML folks have some ideas.
>
> > Maybe it helps you to improve trinity, if not, ignore this mail
> > ;-)
>
> afaics, there's nothing here that trinity can do, once we've
> called _exit(), we're done. Anything that happens afterwards is
> the kernels fault :)
>
> Dave
>
>
>
>
>
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--
Thanks,
//richard
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