netdev - Re: gigaset: freeing an active object

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Date:	Fri, 27 Nov 2015 18:57:57 +0100
From:	Paul Bolle <pebolle@...cali.nl>
To:	Sasha Levin <sasha.levin@...cle.com>
Cc:	isdn@...ux-pingi.de, davem@...emloft.net, tilman@...p.cc,
	gigaset307x-common@...ts.sourceforge.net,
	LKML <linux-kernel@...r.kernel.org>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	syzkaller <syzkaller@...glegroups.com>
Subject: Re: gigaset: freeing an active object

Hi Sascha,

On vr, 2015-11-27 at 10:19 -0500, Sasha Levin wrote:
> Fuzzing with syzkaller on the latest -next kernel produced this error:

(syzkaller is new to me. I'll have to do some web searches.)

> [  413.536749] WARNING: CPU: 6 PID: 25400 at lib/debugobjects.c:263
> debug_print_object+0x1c4/0x1e0()
> [  413.538111] ODEBUG: free active (active state 0) object type:
> timer_list hint: delayed_work_timer_fn+0x0/0x90
> [  413.539598] Modules linked
> in:3470693efef57268844f02f5de3ab392d8cf5e209671ddd87163cb964c510659
> [  413.540448] CPU: 6 PID: 25400 Comm: syzkaller_execu Not tainted
> 4.4.0-rc2-next-20151126-sasha-00005-g00d303e-dirty #2653
> [  413.547614] Call Trace:
> [  413.548077]  [<ffffffffa8e6b5bb>] dump_stack+0x72/0xb7
> [  413.548765]  [<ffffffffa73531d3>] warn_slowpath_common+0x113/0x140
> [  413.551151]  [<ffffffffa73532cb>] warn_slowpath_fmt+0xcb/0x100
> [  413.554295]  [<ffffffffa8ed0194>] debug_print_object+0x1c4/0x1e0
> [  413.556592]  [<ffffffffa8ed1035>]
> __debug_check_no_obj_freed+0x215/0x7a0
> [  413.560526]  [<ffffffffa8ed2b6c>]
> debug_check_no_obj_freed+0x2c/0x40
> [  413.561328]  [<ffffffffa77aac4c>] kfree+0x1fc/0x2f0
> [  413.561970]  [<ffffffffae74b021>] gigaset_freecshw+0xe1/0x120
> [  413.562723]  [<ffffffffae70669d>] gigaset_freecs+0x2ad/0x600
> [  413.564240]  [<ffffffffae74ba60>] gigaset_tty_close+0x210/0x280
> [  413.565774]  [<ffffffffa95ba6f2>] tty_ldisc_close.isra.1+0xc2/0xd0
> [  413.566550]  [<ffffffffa95ba81b>] tty_ldisc_kill+0x4b/0x170
> [  413.567253]  [<ffffffffa95bbba3>] tty_ldisc_release+0x183/0x240
> [  413.568000]  [<ffffffffa95a507c>] tty_release+0xd1c/0xe80
> [  413.570176]  [<ffffffffa78182fa>] __fput+0x32a/0x680
> [  413.570888]  [<ffffffffa78186da>] ____fput+0x1a/0x20
> [  413.571565]  [<ffffffffa73adf5c>] task_work_run+0x19c/0x1e0
> [  413.572290]  [<ffffffffa735cae7>] do_exit+0xdf7/0x28f0
> [  413.576188]  [<ffffffffa735e805>] do_group_exit+0x1b5/0x300
> [  413.576905]  [<ffffffffa7382222>] get_signal+0x1182/0x1360
> [  413.577627]  [<ffffffffa717b553>] do_signal+0x93/0x1690
> [  413.584630]  [<ffffffffa70063b0>] exit_to_usermode_loop+0xc0/0x1e0
> [  413.585412]  [<ffffffffa7007feb>]
> prepare_exit_to_usermode+0x10b/0x140
> [  413.586187]  [<ffffffffb0a12c3e>] retint_user+0x8/0x23

Thanks for the report. I'll look into it.

A question that's nagging me for some time now is: how many people use
gigaset drivers (and, actually ISDN drivers in general) while running
recent kernel releases? I haven't seen reports that suggest people
really do that for some time now.

So, just to be absolutely sure: this was generated with a kernel that
used the ser-gigaset driver without actually using the related hardware,
wasn't it? (That hardware is a clunky, self powered device that requires
a good old serial port.)

Thanks,


Paul Bolle
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