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Message-ID: <s5hbn0lgnvp.wl-tiwai@suse.de>
Date: Mon, 22 Aug 2016 11:21:30 +0200
From: Takashi Iwai <tiwai@...e.de>
To: "Dmitry Vyukov" <dvyukov@...gle.com>
Cc: <alsa-devel@...a-project.org>, "Jaroslav Kysela" <perex@...ex.cz>,
"LKML" <linux-kernel@...r.kernel.org>,
"Alexander Potapenko" <glider@...gle.com>,
"Kostya Serebryany" <kcc@...gle.com>,
"syzkaller" <syzkaller@...glegroups.com>
Subject: Re: sound: deadlock snd_rawmidi_kernel_open/check_and_subscribe_port
On Mon, 22 Aug 2016 02:15:48 +0200,
Dmitry Vyukov wrote:
>
> On Sat, Aug 13, 2016 at 2:43 PM, Dmitry Vyukov <dvyukov@...gle.com> wrote:
> > Hello,
> >
> > While running syzkaller fuzzer on
> > f31494bd05b06b0cdb4da6aebe92eaafab970df6 (Aug 12), I've got the
> > following deadlock report:
> >
> > ======================================================
> > [ INFO: possible circular locking dependency detected ]
> > 4.8.0-rc1+ #11 Not tainted
> > -------------------------------------------------------
> > syz-executor/7154 is trying to acquire lock:
> > (register_mutex#5){+.+.+.}, at: [<ffffffff84fd6d4b>]
> > snd_rawmidi_kernel_open+0x4b/0x260 sound/core/rawmidi.c:341
> >
> > but task is already holding lock:
> > (&grp->list_mutex){++++.+}, at: [<ffffffff850138bb>]
> > check_and_subscribe_port+0x5b/0x5c0 sound/core/seq/seq_ports.c:495
> >
> > which lock already depends on the new lock.
> >
> > the existing dependency chain (in reverse order) is:
> >
> > -> #1 (&grp->list_mutex){++++.+}:
> > [<ffffffff8147a3a8>] lock_acquire+0x208/0x430
> > kernel/locking/lockdep.c:3746
> > [<ffffffff863f6199>] down_read+0x49/0xc0 kernel/locking/rwsem.c:22
> > [< inline >] deliver_to_subscribers
> > sound/core/seq/seq_clientmgr.c:681
> > [<ffffffff85005c5e>] snd_seq_deliver_event+0x35e/0x890
> > sound/core/seq/seq_clientmgr.c:822
> > [<ffffffff85006e96>] snd_seq_kernel_client_dispatch+0x126/0x170
> > sound/core/seq/seq_clientmgr.c:2418
> > [<ffffffff85012c52>] snd_seq_system_broadcast+0xb2/0xf0
> > sound/core/seq/seq_system.c:101
> > [<ffffffff84fff70a>] snd_seq_create_kernel_client+0x24a/0x330
> > sound/core/seq/seq_clientmgr.c:2297
> > [< inline >] snd_virmidi_dev_attach_seq
> > sound/core/seq/seq_virmidi.c:383
> > [<ffffffff8502d29f>] snd_virmidi_dev_register+0x29f/0x750
> > sound/core/seq/seq_virmidi.c:450
> > [<ffffffff84fd208c>] snd_rawmidi_dev_register+0x30c/0xd40
> > sound/core/rawmidi.c:1645
> > [<ffffffff84f816d3>] __snd_device_register.part.0+0x63/0xc0
> > sound/core/device.c:164
> > [< inline >] __snd_device_register sound/core/device.c:162
> > [<ffffffff84f8235d>] snd_device_register_all+0xad/0x110
> > sound/core/device.c:212
> > [<ffffffff84f7546f>] snd_card_register+0xef/0x6c0 sound/core/init.c:749
> > [<ffffffff85040b7f>] snd_virmidi_probe+0x3ef/0x590
> > sound/drivers/virmidi.c:123
> > [<ffffffff833ebf7b>] platform_drv_probe+0x8b/0x170
> > drivers/base/platform.c:564
> > [< inline >] really_probe drivers/base/dd.c:377
> > [<ffffffff833e5993>] driver_probe_device+0x563/0xcc0
> > drivers/base/dd.c:499
> > [<ffffffff833e653d>] __device_attach_driver+0x21d/0x2e0
> > drivers/base/dd.c:594
> > [<ffffffff833df38f>] bus_for_each_drv+0x13f/0x1d0 drivers/base/bus.c:463
> > [<ffffffff833e51ef>] __device_attach+0x1ef/0x300 drivers/base/dd.c:651
> > [<ffffffff833e669a>] device_initial_probe+0x1a/0x20 drivers/base/dd.c:698
> > [<ffffffff833e2999>] bus_probe_device+0x1e9/0x290 drivers/base/bus.c:557
> > [<ffffffff833dc459>] device_add+0xc49/0x14c0 drivers/base/core.c:1120
> > [<ffffffff833eb629>] platform_device_add+0x2f9/0x7b0
> > drivers/base/platform.c:403
> > [<ffffffff833ed3b2>] platform_device_register_full+0x392/0x4b0
> > drivers/base/platform.c:536
> > [< inline >] platform_device_register_resndata
> > ./include/linux/platform_device.h:111
> > [< inline >] platform_device_register_simple
> > ./include/linux/platform_device.h:140
> > [<ffffffff8870fabd>] alsa_card_virmidi_init+0x104/0x1da
> > sound/drivers/virmidi.c:172
> > [<ffffffff81002330>] do_one_initcall+0xa0/0x2b0 init/main.c:778
> > [< inline >] do_initcall_level init/main.c:843
> > [< inline >] do_initcalls init/main.c:851
> > [< inline >] do_basic_setup init/main.c:869
> > [<ffffffff88604d11>] kernel_init_freeable+0x47b/0x534 init/main.c:1016
> > [<ffffffff863e2f53>] kernel_init+0x13/0x180 init/main.c:942
> > [<ffffffff863fbdcf>] ret_from_fork+0x1f/0x40
> > arch/x86/entry/entry_64.S:393
> >
> > -> #0 (register_mutex#5){+.+.+.}:
> > [< inline >] check_prev_add kernel/locking/lockdep.c:1829
> > [< inline >] check_prevs_add kernel/locking/lockdep.c:1939
> > [< inline >] validate_chain kernel/locking/lockdep.c:2266
> > [<ffffffff814791f4>] __lock_acquire+0x4d44/0x4d80
> > kernel/locking/lockdep.c:3335
> > [<ffffffff8147a3a8>] lock_acquire+0x208/0x430
> > kernel/locking/lockdep.c:3746
> > [< inline >] __mutex_lock_common kernel/locking/mutex.c:521
> > [<ffffffff863f0ef1>] mutex_lock_nested+0xb1/0xa20
> > kernel/locking/mutex.c:621
> > [<ffffffff84fd6d4b>] snd_rawmidi_kernel_open+0x4b/0x260
> > sound/core/rawmidi.c:341
> > [<ffffffff8502e7c7>] midisynth_subscribe+0xf7/0x350
> > sound/core/seq/seq_midi.c:188
> > [< inline >] subscribe_port sound/core/seq/seq_ports.c:427
> > [<ffffffff85013cc7>] check_and_subscribe_port+0x467/0x5c0
> > sound/core/seq/seq_ports.c:510
> > [<ffffffff85015da9>] snd_seq_port_connect+0x2c9/0x500
> > sound/core/seq/seq_ports.c:579
> > [<ffffffff850079b8>] snd_seq_ioctl_subscribe_port+0x1d8/0x2b0
> > sound/core/seq/seq_clientmgr.c:1480
> > [<ffffffff84ffe9e4>] snd_seq_do_ioctl+0x184/0x1e0
> > sound/core/seq/seq_clientmgr.c:2225
> > [<ffffffff84ffeae8>] snd_seq_kernel_client_ctl+0xa8/0x110
> > sound/core/seq/seq_clientmgr.c:2440
> > [<ffffffff85027664>] snd_seq_oss_midi_open+0x3b4/0x610
> > sound/core/seq/oss/seq_oss_midi.c:375
> > [<ffffffff85023d67>] snd_seq_oss_synth_setup_midi+0x107/0x4c0
> > sound/core/seq/oss/seq_oss_synth.c:281
> > [<ffffffff8501b0a8>] snd_seq_oss_open+0x748/0x8d0
> > sound/core/seq/oss/seq_oss_init.c:274
> > [<ffffffff85019d8a>] odev_open+0x6a/0x90 sound/core/seq/oss/seq_oss.c:138
> > [<ffffffff84f7040f>] soundcore_open+0x30f/0x640 sound/sound_core.c:639
> > [<ffffffff818069ea>] chrdev_open+0x22a/0x4c0 fs/char_dev.c:392
> > [<ffffffff817f146f>] do_dentry_open+0x69f/0xca0 fs/open.c:736
> > [<ffffffff817f4aa5>] vfs_open+0x105/0x220 fs/open.c:849
> > [< inline >] do_last fs/namei.c:3374
> > [<ffffffff8182c35d>] path_openat+0x1efd/0x2f60 fs/namei.c:3497
> > [<ffffffff81830b6e>] do_filp_open+0x18e/0x250 fs/namei.c:3532
> > [<ffffffff817f53c1>] do_sys_open+0x201/0x420 fs/open.c:1036
> > [< inline >] SYSC_open fs/open.c:1054
> > [<ffffffff817f560d>] SyS_open+0x2d/0x40 fs/open.c:1049
> > [<ffffffff863fbb80>] entry_SYSCALL_64_fastpath+0x23/0xc1
> > arch/x86/entry/entry_64.S:207
> >
> > other info that might help us debug this:
> >
> > Possible unsafe locking scenario:
> >
> > CPU0 CPU1
> > ---- ----
> > lock(&grp->list_mutex);
> > lock(register_mutex#5);
> > lock(&grp->list_mutex);
> > lock(register_mutex#5);
> >
> > *** DEADLOCK ***
> >
> > 2 locks held by syz-executor/7154:
> > #0: (register_mutex#4){+.+.+.}, at: [<ffffffff85019d7f>]
> > odev_open+0x5f/0x90 sound/core/seq/oss/seq_oss.c:137
> > #1: (&grp->list_mutex){++++.+}, at: [<ffffffff850138bb>]
> > check_and_subscribe_port+0x5b/0x5c0 sound/core/seq/seq_ports.c:495
> >
> > stack backtrace:
> > CPU: 0 PID: 7154 Comm: syz-executor Not tainted 4.8.0-rc1+ #11
> > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
> > ffffffff878b7680 ffff880038b670f0 ffffffff82a5f719 ffffffff00000000
> > fffffbfff0f16ed0 ffffffff8901a0d0 ffffffff8901a0d0 ffffffff890191a0
> > ffff88003da2cf08 ffff88003da2c6c0 ffff880038b67140 ffffffff814708a8
> > Call Trace:
> > [< inline >] __dump_stack lib/dump_stack.c:15
> > [<ffffffff82a5f719>] dump_stack+0x12e/0x185 lib/dump_stack.c:51
> > [<ffffffff814708a8>] print_circular_bug+0x288/0x340
> > kernel/locking/lockdep.c:1202
> > [< inline >] check_prev_add kernel/locking/lockdep.c:1829
> > [< inline >] check_prevs_add kernel/locking/lockdep.c:1939
> > [< inline >] validate_chain kernel/locking/lockdep.c:2266
> > [<ffffffff814791f4>] __lock_acquire+0x4d44/0x4d80 kernel/locking/lockdep.c:3335
> > [<ffffffff8147a3a8>] lock_acquire+0x208/0x430 kernel/locking/lockdep.c:3746
> > [< inline >] __mutex_lock_common kernel/locking/mutex.c:521
> > [<ffffffff863f0ef1>] mutex_lock_nested+0xb1/0xa20 kernel/locking/mutex.c:621
> > [<ffffffff84fd6d4b>] snd_rawmidi_kernel_open+0x4b/0x260
> > sound/core/rawmidi.c:341
> > [<ffffffff8502e7c7>] midisynth_subscribe+0xf7/0x350
> > sound/core/seq/seq_midi.c:188
> > [< inline >] subscribe_port sound/core/seq/seq_ports.c:427
> > [<ffffffff85013cc7>] check_and_subscribe_port+0x467/0x5c0
> > sound/core/seq/seq_ports.c:510
> > [<ffffffff85015da9>] snd_seq_port_connect+0x2c9/0x500
> > sound/core/seq/seq_ports.c:579
> > [<ffffffff850079b8>] snd_seq_ioctl_subscribe_port+0x1d8/0x2b0
> > sound/core/seq/seq_clientmgr.c:1480
> > [<ffffffff84ffe9e4>] snd_seq_do_ioctl+0x184/0x1e0
> > sound/core/seq/seq_clientmgr.c:2225
> > [<ffffffff84ffeae8>] snd_seq_kernel_client_ctl+0xa8/0x110
> > sound/core/seq/seq_clientmgr.c:2440
> > [<ffffffff85027664>] snd_seq_oss_midi_open+0x3b4/0x610
> > sound/core/seq/oss/seq_oss_midi.c:375
> > [<ffffffff85023d67>] snd_seq_oss_synth_setup_midi+0x107/0x4c0
> > sound/core/seq/oss/seq_oss_synth.c:281
> > [<ffffffff8501b0a8>] snd_seq_oss_open+0x748/0x8d0
> > sound/core/seq/oss/seq_oss_init.c:274
> > [<ffffffff85019d8a>] odev_open+0x6a/0x90 sound/core/seq/oss/seq_oss.c:138
> > [<ffffffff84f7040f>] soundcore_open+0x30f/0x640 sound/sound_core.c:639
> > [<ffffffff818069ea>] chrdev_open+0x22a/0x4c0 fs/char_dev.c:392
> > [<ffffffff817f146f>] do_dentry_open+0x69f/0xca0 fs/open.c:736
> > [<ffffffff817f4aa5>] vfs_open+0x105/0x220 fs/open.c:849
> > [< inline >] do_last fs/namei.c:3374
> > [<ffffffff8182c35d>] path_openat+0x1efd/0x2f60 fs/namei.c:3497
> > [<ffffffff81830b6e>] do_filp_open+0x18e/0x250 fs/namei.c:3532
> > [<ffffffff817f53c1>] do_sys_open+0x201/0x420 fs/open.c:1036
> > [< inline >] SYSC_open fs/open.c:1054
> > [<ffffffff817f560d>] SyS_open+0x2d/0x40 fs/open.c:1049
> > [<ffffffff863fbb80>] entry_SYSCALL_64_fastpath+0x23/0xc1
> > arch/x86/entry/entry_64.S:207
>
>
> Ping. Still happens on HEAD.
Sorry, I've been on vacation in the last week.
I'll take a look once after digesting the whole backlogs...
thanks,
Takashi
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