On Fri, 27 Oct 2017 10:11:18 +0200, Dmitry Vyukov wrote: > > On Fri, Oct 27, 2017 at 10:09 AM, syzbot > <bot+7feb8de6b4d6bf810cf098bef942cc387e79d0ad@xxxxxxxxxxxxxxxxxxxxxxxxx> > wrote: > > Hello, > > > > syzkaller hit the following crash on > > 2bd6bf03f4c1c59381d62c61d03f6cc3fe71f66e > > git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next.git/master > > compiler: gcc (GCC) 7.1.1 20170620 > > .config is attached > > Raw console output is attached. > > C reproducer is attached > > syzkaller reproducer is attached. See https://goo.gl/kgGztJ > > for information about syzkaller reproducers > > > > > > ============================================ > > WARNING: possible recursive locking detected > > 4.14.0-rc1+ #88 Not tainted > > -------------------------------------------- > > syzkaller883997/2981 is trying to acquire lock: > > (&grp->list_mutex){++++}, at: [<ffffffff83d4dd49>] deliver_to_subscribers > > sound/core/seq/seq_clientmgr.c:666 [inline] > > (&grp->list_mutex){++++}, at: [<ffffffff83d4dd49>] > > snd_seq_deliver_event+0x279/0x790 sound/core/seq/seq_clientmgr.c:807 > > > > but task is already holding lock: > > (&grp->list_mutex){++++}, at: [<ffffffff83d4dd49>] deliver_to_subscribers > > sound/core/seq/seq_clientmgr.c:666 [inline] > > (&grp->list_mutex){++++}, at: [<ffffffff83d4dd49>] > > snd_seq_deliver_event+0x279/0x790 sound/core/seq/seq_clientmgr.c:807 > > > > other info that might help us debug this: > > Possible unsafe locking scenario: > > > > CPU0 > > ---- > > lock(&grp->list_mutex); > > lock(&grp->list_mutex); > > > > *** DEADLOCK *** > > > > May be due to missing lock nesting notation > > > > 2 locks held by syzkaller883997/2981: > > #0: (register_mutex#4){+.+.}, at: [<ffffffff83d60ada>] > > odev_release+0x4a/0x70 sound/core/seq/oss/seq_oss.c:152 > > #1: (&grp->list_mutex){++++}, at: [<ffffffff83d4dd49>] > > deliver_to_subscribers sound/core/seq/seq_clientmgr.c:666 [inline] > > #1: (&grp->list_mutex){++++}, at: [<ffffffff83d4dd49>] > > snd_seq_deliver_event+0x279/0x790 sound/core/seq/seq_clientmgr.c:807 > > > > stack backtrace: > > CPU: 1 PID: 2981 Comm: syzkaller883997 Not tainted 4.14.0-rc1+ #88 > > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS > > Google 01/01/2011 > > Call Trace: > > __dump_stack lib/dump_stack.c:16 [inline] > > dump_stack+0x194/0x257 lib/dump_stack.c:52 > > print_deadlock_bug kernel/locking/lockdep.c:1797 [inline] > > check_deadlock kernel/locking/lockdep.c:1844 [inline] > > validate_chain kernel/locking/lockdep.c:2453 [inline] > > __lock_acquire+0x1232/0x4620 kernel/locking/lockdep.c:3498 > > lock_acquire+0x1d5/0x580 kernel/locking/lockdep.c:4002 > > down_read+0x96/0x150 kernel/locking/rwsem.c:23 > > deliver_to_subscribers sound/core/seq/seq_clientmgr.c:666 [inline] > > snd_seq_deliver_event+0x279/0x790 sound/core/seq/seq_clientmgr.c:807 > > snd_seq_kernel_client_dispatch+0x11e/0x150 > > sound/core/seq/seq_clientmgr.c:2309 > > dummy_input+0x2c4/0x400 sound/core/seq/seq_dummy.c:104 > > snd_seq_deliver_single_event.constprop.11+0x2fb/0x940 > > sound/core/seq/seq_clientmgr.c:621 > > deliver_to_subscribers sound/core/seq/seq_clientmgr.c:676 [inline] > > snd_seq_deliver_event+0x318/0x790 sound/core/seq/seq_clientmgr.c:807 > > snd_seq_kernel_client_dispatch+0x11e/0x150 > > sound/core/seq/seq_clientmgr.c:2309 > > dummy_input+0x2c4/0x400 sound/core/seq/seq_dummy.c:104 > > snd_seq_deliver_single_event.constprop.11+0x2fb/0x940 > > sound/core/seq/seq_clientmgr.c:621 > > snd_seq_deliver_event+0x12c/0x790 sound/core/seq/seq_clientmgr.c:818 > > snd_seq_kernel_client_dispatch+0x11e/0x150 > > sound/core/seq/seq_clientmgr.c:2309 > > snd_seq_oss_dispatch sound/core/seq/oss/seq_oss_device.h:150 [inline] > > snd_seq_oss_midi_reset+0x44b/0x700 sound/core/seq/oss/seq_oss_midi.c:481 > > snd_seq_oss_synth_reset+0x398/0x980 sound/core/seq/oss/seq_oss_synth.c:416 > > snd_seq_oss_reset+0x6c/0x260 sound/core/seq/oss/seq_oss_init.c:448 > > snd_seq_oss_release+0x71/0x120 sound/core/seq/oss/seq_oss_init.c:425 > > odev_release+0x52/0x70 sound/core/seq/oss/seq_oss.c:153 > > __fput+0x333/0x7f0 fs/file_table.c:210 > > ____fput+0x15/0x20 fs/file_table.c:244 > > task_work_run+0x199/0x270 kernel/task_work.c:112 > > exit_task_work include/linux/task_work.h:21 [inline] > > do_exit+0xa52/0x1b40 kernel/exit.c:865 > > do_group_exit+0x149/0x400 kernel/exit.c:968 > > SYSC_exit_group kernel/exit.c:979 [inline] > > SyS_exit_group+0x1d/0x20 kernel/exit.c:977 > > entry_SYSCALL_64_fastpath+0x1f/0xbe > > RIP: 0033:0x442c58 > > RSP: 002b:00007ffd15d4f8d8 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7 > > RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 0000000000442c58 > > RDX: 0000000000000000 RSI: 000000000000003c RDI: 0000000000000000 > > RBP: 0000000000000082 R08: 00000000000000e7 R09: ffffffffffffffd0 > > R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000401ca0 > > R13: 0000000000401d30 R14 > > I've just re-reproduced this on upstream > 15f859ae5c43c7f0a064ed92d33f7a5bc5de6de0 (Oct 26): > > ============================================ > WARNING: possible recursive locking detected > 4.14.0-rc6+ #10 Not tainted > -------------------------------------------- > a.out/3062 is trying to acquire lock: > (&grp->list_mutex){++++}, at: [<ffffffff83d28879>] > deliver_to_subscribers sound/core/seq/seq_clientmgr.c:666 [inline] > (&grp->list_mutex){++++}, at: [<ffffffff83d28879>] > snd_seq_deliver_event+0x279/0x790 sound/core/seq/seq_clientmgr.c:807 > > but task is already holding lock: > (&grp->list_mutex){++++}, at: [<ffffffff83d28879>] > deliver_to_subscribers sound/core/seq/seq_clientmgr.c:666 [inline] > (&grp->list_mutex){++++}, at: [<ffffffff83d28879>] > snd_seq_deliver_event+0x279/0x790 sound/core/seq/seq_clientmgr.c:807 > > other info that might help us debug this: > Possible unsafe locking scenario: > > CPU0 > ---- > lock(&grp->list_mutex); > lock(&grp->list_mutex); > > *** DEADLOCK *** > > May be due to missing lock nesting notation Indeed, this looks more like a simply missing nesting annotation. A totally untested patch is below. thanks, Takashi --- diff --git a/sound/core/seq/seq_clientmgr.c b/sound/core/seq/seq_clientmgr.c index 6c9cba2166d9..d10c780dfd54 100644 --- a/sound/core/seq/seq_clientmgr.c +++ b/sound/core/seq/seq_clientmgr.c @@ -663,7 +663,7 @@ static int deliver_to_subscribers(struct snd_seq_client *client, if (atomic) read_lock(&grp->list_lock); else - down_read(&grp->list_mutex); + down_read_nested(&grp->list_mutex, hop); list_for_each_entry(subs, &grp->list_head, src_list) { /* both ports ready? */ if (atomic_read(&subs->ref_count) != 2) _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
