Messages in this thread Patch in this message | | | Date | Wed, 28 Apr 2021 09:30:18 -0400 | From | Steven Rostedt <> | Subject | Re: [syzbot] possible deadlock in vm_mmap_pgoff |
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On Wed, 28 Apr 2021 14:15:22 +0800 Hillf Danton <hdanton@sina.com> wrote:
> On Tue, 27 Apr 2021 08:18:27 > > Hello, > > > > syzbot found the following issue on: > > > > HEAD commit: 7af08140 Revert "gcov: clang: fix clang-11+ build" > > git tree: upstream > > console output: https://syzkaller.appspot.com/x/log.txt?x=17d57dfed00000 > > kernel config: https://syzkaller.appspot.com/x/.config?x=76c0382ceab56d34 > > dashboard link: https://syzkaller.appspot.com/bug?extid=f619f7c0a2a5f87694e6 > > > > Unfortunately, I don't have any reproducer for this issue yet. > > > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > > Reported-by: syzbot+f619f7c0a2a5f87694e6@syzkaller.appspotmail.com > > > > ====================================================== > > WARNING: possible circular locking dependency detected > > 5.12.0-rc8-syzkaller #0 Not tainted > > ------------------------------------------------------ > > syz-executor.1/16055 is trying to acquire lock: > > ffffffff8bfe2bc8 (event_mutex){+.+.}-{3:3}, at: perf_trace_destroy+0x23/0xf0 kernel/trace/trace_event_perf.c:241 > > > > but task is already holding lock: > > ffff88801b887258 (&mm->mmap_lock#2){++++}-{3:3}, at: mmap_write_lock_killable include/linux/mmap_lock.h:87 [inline] > > ffff88801b887258 (&mm->mmap_lock#2){++++}-{3:3}, at: vm_mmap_pgoff+0x15c/0x290 mm/util.c:517 > > > > which lock already depends on the new lock. > > > > > > the existing dependency chain (in reverse order) is: > > > > -> #3 (&mm->mmap_lock#2){++++}-{3:3}: > > down_write_killable+0x95/0x170 kernel/locking/rwsem.c:1417 > > mmap_write_lock_killable include/linux/mmap_lock.h:87 [inline] > > dup_mmap kernel/fork.c:480 [inline] > > dup_mm+0x12e/0x1380 kernel/fork.c:1368 > > copy_mm kernel/fork.c:1424 [inline] > > copy_process+0x2bc8/0x71a0 kernel/fork.c:2113 > > kernel_clone+0xe7/0xab0 kernel/fork.c:2500 > > __do_sys_clone+0xc8/0x110 kernel/fork.c:2617 > > do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46 > > entry_SYSCALL_64_after_hwframe+0x44/0xae > > > > -> #2 (dup_mmap_sem){++++}-{0:0}: > > percpu_down_write+0x95/0x440 kernel/locking/percpu-rwsem.c:217 > > register_for_each_vma+0x2c/0xc10 kernel/events/uprobes.c:1040 > > __uprobe_register+0x5c2/0x850 kernel/events/uprobes.c:1181 > > trace_uprobe_enable kernel/trace/trace_uprobe.c:1065 [inline] > > probe_event_enable+0x357/0xa00 kernel/trace/trace_uprobe.c:1134 > > trace_uprobe_register+0x443/0x880 kernel/trace/trace_uprobe.c:1461 > > perf_trace_event_reg kernel/trace/trace_event_perf.c:129 [inline] > > perf_trace_event_init+0x549/0xa20 kernel/trace/trace_event_perf.c:204 > > perf_uprobe_init+0x16f/0x210 kernel/trace/trace_event_perf.c:336 > > perf_uprobe_event_init+0xff/0x1c0 kernel/events/core.c:9754 > > perf_try_init_event+0x12a/0x560 kernel/events/core.c:11071 > > perf_init_event kernel/events/core.c:11123 [inline] > > perf_event_alloc.part.0+0xe3b/0x3960 kernel/events/core.c:11403 > > perf_event_alloc kernel/events/core.c:11785 [inline] > > __do_sys_perf_event_open+0x647/0x2e60 kernel/events/core.c:11883 > > do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46 > > entry_SYSCALL_64_after_hwframe+0x44/0xae > > > > -> #1 (&uprobe->register_rwsem){+.+.}-{3:3}: > > down_write+0x92/0x150 kernel/locking/rwsem.c:1406 > > __uprobe_register+0x531/0x850 kernel/events/uprobes.c:1177 > > trace_uprobe_enable kernel/trace/trace_uprobe.c:1065 [inline] > > probe_event_enable+0x357/0xa00 kernel/trace/trace_uprobe.c:1134 > > trace_uprobe_register+0x443/0x880 kernel/trace/trace_uprobe.c:1461 > > perf_trace_event_reg kernel/trace/trace_event_perf.c:129 [inline] > > perf_trace_event_init+0x549/0xa20 kernel/trace/trace_event_perf.c:204 > > perf_uprobe_init+0x16f/0x210 kernel/trace/trace_event_perf.c:336 > > perf_uprobe_event_init+0xff/0x1c0 kernel/events/core.c:9754 > > perf_try_init_event+0x12a/0x560 kernel/events/core.c:11071 > > perf_init_event kernel/events/core.c:11123 [inline] > > perf_event_alloc.part.0+0xe3b/0x3960 kernel/events/core.c:11403 > > perf_event_alloc kernel/events/core.c:11785 [inline] > > __do_sys_perf_event_open+0x647/0x2e60 kernel/events/core.c:11883 > > do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46 > > entry_SYSCALL_64_after_hwframe+0x44/0xae > > > > -> #0 (event_mutex){+.+.}-{3:3}: > > check_prev_add kernel/locking/lockdep.c:2937 [inline] > > check_prevs_add kernel/locking/lockdep.c:3060 [inline] > > validate_chain kernel/locking/lockdep.c:3675 [inline] > > __lock_acquire+0x2b14/0x54c0 kernel/locking/lockdep.c:4901 > > lock_acquire kernel/locking/lockdep.c:5511 [inline] > > lock_acquire+0x1ab/0x740 kernel/locking/lockdep.c:5476 > > __mutex_lock_common kernel/locking/mutex.c:949 [inline] > > __mutex_lock+0x139/0x1120 kernel/locking/mutex.c:1096 > > perf_trace_destroy+0x23/0xf0 kernel/trace/trace_event_perf.c:241 > > _free_event+0x2ee/0x1380 kernel/events/core.c:4863 > > put_event kernel/events/core.c:4957 [inline] > > perf_mmap_close+0x572/0xe10 kernel/events/core.c:6002 > > remove_vma+0xae/0x170 mm/mmap.c:180 > > remove_vma_list mm/mmap.c:2653 [inline] > > __do_munmap+0x74f/0x11a0 mm/mmap.c:2909 > > do_munmap mm/mmap.c:2917 [inline] > > munmap_vma_range mm/mmap.c:598 [inline] > > mmap_region+0x85a/0x1730 mm/mmap.c:1750 > > do_mmap+0xcff/0x11d0 mm/mmap.c:1581 > > vm_mmap_pgoff+0x1b7/0x290 mm/util.c:519 > > ksys_mmap_pgoff+0x49c/0x620 mm/mmap.c:1632 > > do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46 > > entry_SYSCALL_64_after_hwframe+0x44/0xae > > > > other info that might help us debug this: > > > > Chain exists of: > > event_mutex --> dup_mmap_sem --> &mm->mmap_lock#2 > > > > Possible unsafe locking scenario: > > > > CPU0 CPU1 > > ---- ---- > > lock(&mm->mmap_lock#2); > > lock(dup_mmap_sem); > > lock(&mm->mmap_lock#2); > > lock(event_mutex); > > > > *** DEADLOCK *** > > Break the lock chain by asking kworker to destroy perf event. > Thoughts other than workqueue are appreciated.
I think this could cause a problem with the delay.
This is called from event->destroy()
if (event->destroy) event->destroy(event); module_put(pmu->module);
What if this event is in that module, and we just unloaded it?
Then the workqueue would try to modify the module text that no longer exists. Right?
I Cc'd some people that understand this code better.
-- Steve
> > +++ x/kernel/trace/trace_event_perf.c > @@ -236,14 +236,22 @@ int perf_trace_init(struct perf_event *p > return ret; > } > > -void perf_trace_destroy(struct perf_event *p_event) > +static void perf_trace_destroy_work_fn(struct work_struct *w) > { > + struct perf_event *p_event = container_of(w, struct perf_event, > + destroy_work); > mutex_lock(&event_mutex); > perf_trace_event_close(p_event); > perf_trace_event_unreg(p_event); > mutex_unlock(&event_mutex); > } > > +void perf_trace_destroy(struct perf_event *p_event) > +{ > + INIT_WORK(&p_event->destroy_work, perf_trace_destroy_work_fn); > + queue_work(system_unbound_wq, &p_event->destroy_work); > +} > + > #ifdef CONFIG_KPROBE_EVENTS > int perf_kprobe_init(struct perf_event *p_event, bool is_retprobe) > {
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