On Tue, Sep 6, 2016 at 3:43 PM, Takashi Iwai tiwai@suse.de wrote:
On Tue, 06 Sep 2016 15:09:25 +0200, Dmitry Vyukov wrote:
On Tue, Sep 6, 2016 at 3:00 PM, Takashi Iwai tiwai@suse.de wrote:
On Sat, 03 Sep 2016 14:35:15 +0200, Dmitry Vyukov wrote:
Hello,
The following program causes either division error or hangs kernel:
https://gist.githubusercontent.com/dvyukov/b1f33be3bfcc15d629e10db483bee1e4/...
divide error: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN Dumping ftrace buffer: (ftrace buffer empty) Modules linked in: CPU: 1 PID: 27320 Comm: syz-executor Not tainted 4.8.0-rc3-next-20160825+ #8 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 task: ffff88003c9b2280 task.stack: ffff880027280000 RIP: 0010:[<ffffffff858e1a6c>] [< inline >] ktime_divns include/linux/ktime.h:195 RIP: 0010:[<ffffffff858e1a6c>] [<ffffffff858e1a6c>] snd_hrtimer_callback+0x1bc/0x3c0 sound/core/hrtimer.c:62 RSP: 0018:ffff88003ed07dd8 EFLAGS: 00010006 RAX: 0000000000004801 RBX: ffff88003d3a0a88 RCX: 0000000000000000 RDX: 0000000000000000 RSI: ffff88003d3a0aa0 RDI: ffffffff886b69a8 RBP: ffff88003ed07e30 R08: 0000010e85417665 R09: ffff88007fff7048 R10: ffff88007fff7058 R11: ffff88007fff7050 R12: ffff88003d00f840 R13: ffff88003d00f8f4 R14: ffff88003d00f970 R15: ffff88003d3a0a80 FS: 0000000000000000(0000) GS:ffff88003ed00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f4152126db8 CR3: 000000006b896000 CR4: 00000000000006e0 DR0: 000000000000001e DR1: 000000000000001e DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600 Stack: 0000000000000000 ffff88003d3a0aa0 ffff88003d00f8f8 0000000000004801 ffff88003d3a0ae0 0000000000000000 ffff88003d3a0a88 0000000000000001 ffff88003ed1b400 dffffc0000000000 0000000000000001 ffff88003ed07f28 Call Trace:
<IRQ> [< inline >] __run_hrtimer kernel/time/hrtimer.c:1238 [<ffffffff81504335>] __hrtimer_run_queues+0x325/0xe70 kernel/time/hrtimer.c:1302 [<ffffffff81506ceb>] hrtimer_interrupt+0x18b/0x420 kernel/time/hrtimer.c:1336 [<ffffffff8126d8df>] local_apic_timer_interrupt+0x6f/0xe0 arch/x86/kernel/apic/apic.c:933 [<ffffffff86e13056>] smp_apic_timer_interrupt+0x76/0xa0 arch/x86/kernel/apic/apic.c:957 [<ffffffff86e1210c>] apic_timer_interrupt+0x8c/0xa0 arch/x86/entry/entry_64.S:487 <EOI> [< inline >] rcu_lock_release include/linux/rcupdate.h:494 [< inline >] rcu_read_unlock include/linux/rcupdate.h:927 [<ffffffff81839f55>] unlock_page_memcg+0x95/0x130 mm/memcontrol.c:1680 [< inline >] page_remove_file_rmap mm/rmap.c:1343 [<ffffffff817b742c>] page_remove_rmap+0x1cc/0x8e0 mm/rmap.c:1394 [< inline >] zap_pte_range mm/memory.c:1170 [< inline >] zap_pmd_range mm/memory.c:1257 [< inline >] zap_pud_range mm/memory.c:1278 [<ffffffff81789119>] unmap_page_range+0xf89/0x1ba0 mm/memory.c:1299 [<ffffffff81789e31>] unmap_single_vma+0x101/0x260 mm/memory.c:1344 [<ffffffff8178a741>] unmap_vmas+0xf1/0x1b0 [<ffffffff817a5aab>] exit_mmap+0x22b/0x420 mm/mmap.c:2787 [< inline >] __mmput kernel/fork.c:770 [<ffffffff8137c576>] mmput+0xd6/0x3c0 kernel/fork.c:790 [< inline >] exit_mm kernel/exit.c:512 [<ffffffff813940e8>] do_exit+0x738/0x2e70 kernel/exit.c:815 [<ffffffff81396998>] do_group_exit+0x108/0x330 kernel/exit.c:958 [<ffffffff813ba4aa>] get_signal+0x62a/0x15d0 kernel/signal.c:2307 [<ffffffff81202333>] do_signal+0x83/0x1f60 arch/x86/kernel/signal.c:805 [<ffffffff81006345>] exit_to_usermode_loop+0x1a5/0x210 arch/x86/entry/common.c:163 [< inline >] prepare_exit_to_usermode arch/x86/entry/common.c:198 [< inline >] syscall_return_slowpath arch/x86/entry/common.c:267 [<ffffffff81008be0>] do_syscall_64+0x4c0/0x640 arch/x86/entry/common.c:293 [<ffffffff86e107c3>] entry_SYSCALL64_slow_path+0x25/0x25 Code: cb a2 ce fb 8b 0d f5 21 70 05 48 0f af 4d d0 48 85 c9 0f 88 6a 01 00 00 48 89 4d a8 e8 ae a2 ce fb 48 8b 45 c0 48 8b 4d a8 48 99 <48> f7 f9 48 01 45 d0 e8 98 a2 ce fb 4c 89 fa 48 b8 00 00 00 00 RIP [< inline >] ktime_divns include/linux/ktime.h:195 RIP [<ffffffff858e1a6c>] snd_hrtimer_callback+0x1bc/0x3c0 sound/core/hrtimer.c:62 RSP <ffff88003ed07dd8> ---[ end trace e1a6d1e5a6136d50 ]---
or:
INFO: rcu_sched detected stalls on CPUs/tasks: 0-...: (1 GPs behind) idle=203/140000000000001/0 softirq=923090/923091 fqs=6490 (detected by 1, t=26002 jiffies, g=508022, c=508021, q=20) Task dump for CPU 0: a.out R running task 28848 31756 4047 0x0000000a 0000000000000000 0000000000000282 0000000000000000 ffff880066a9b430 ffff880066a9b430 ffff8800667cfae0 0000000000000282 0000000000000000 0000000000000000 0000000000000000 000003a0184674dd dffffc0000000000 Call Trace: [< inline >] spin_unlock_irqrestore ./include/linux/spinlock.h:362 [<ffffffff858db3dd>] snd_timer_start1+0xdd/0x740 sound/core/timer.c:477 [<ffffffff858dbb25>] snd_timer_continue+0x45/0x80 sound/core/timer.c:606 [< inline >] snd_timer_user_continue sound/core/timer.c:1835 [< inline >] __snd_timer_user_ioctl sound/core/timer.c:1902 [<ffffffff858df299>] snd_timer_user_ioctl+0xe99/0x2470 sound/core/timer.c:1917 [< inline >] vfs_ioctl fs/ioctl.c:43 [<ffffffff818a1dfc>] do_vfs_ioctl+0x18c/0x1080 fs/ioctl.c:675 [< inline >] SYSC_ioctl fs/ioctl.c:690 [<ffffffff818a2d7f>] SyS_ioctl+0x8f/0xc0 fs/ioctl.c:681 [<ffffffff86e10700>] entry_SYSCALL_64_fastpath+0x23/0xc1 arch/x86/entry/entry_64.S:208
I am on 0f98f121e1670eaa2a2fbb675e07d6ba7f0e146f of linux-next with the following diff in sound/core/timer.c (one is a fix for another division by 0):
diff --git a/sound/core/timer.c b/sound/core/timer.c index 9a6157e..3e55c6d 100644 --- a/sound/core/timer.c +++ b/sound/core/timer.c @@ -813,6 +813,7 @@ int snd_timer_new(struct snd_card *card, char *id, struct snd_timer_id *tid, timer->tmr_subdevice = tid->subdevice; if (id) strlcpy(timer->id, id, sizeof(timer->id));
timer->sticks = 1; INIT_LIST_HEAD(&timer->device_list); INIT_LIST_HEAD(&timer->open_list_head); INIT_LIST_HEAD(&timer->active_list_head);@@ -1958,6 +1959,7 @@ static ssize_t snd_timer_user_read(struct file *file, char __user *buffer, tu->qused--; spin_unlock_irq(&tu->qlock);
mutex_lock(&tu->ioctl_lock); if (tu->tread) { if (copy_to_user(buffer, &tu->tqueue[qhead], sizeof(struct snd_timer_tread)))@@ -1967,6 +1969,7 @@ static ssize_t snd_timer_user_read(struct file *file, char __user *buffer, sizeof(struct snd_timer_read))) err = -EFAULT; }
mutex_unlock(&tu->ioctl_lock); spin_lock_irq(&tu->qlock); if (err < 0)I couldn't trigger the bug any longer after merging for-linus branch of sound.git tree: git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound.git
But I thought it got fixed by sticks=1 in the above. Maybe it's a combination, as it contains yet another timer fix by Vegard.
You mean that my local changes are a combination of two patches? But I would not expect that addition of mutex_lock/unlock can affect division by 0. Or you mean that there some other fix by Vegard? What is it?
There is another fix 8ddc05638ee42b18ba4fe99b5fb647fa3ad20456 ALSA: timer: fix NULL pointer dereference on memory allocation failure But it's likely irrelevant.
I retested now, and could see the latter stack trace, the rcu tall, while running the program, although it doesn't lead to a complete freeze and the system is restored once after the program quits.
Do you really see the zero-division error with sticks=1 fix? That's unexpected.
Yes, just reproduced it again. I am on 0693c28cfc8e25f18c25b65a8942c026f1854a3c of linux-next now, so I already have: commit 6b760bb2c63a9e322c0e4a0b5daf335ad93d5a33 ALSA: timer: fix division by zero after SNDRV_TIMER_IOCTL_CONTINUE
Compiled the program verbatim and run it using stress utility (http s://godoc.org/golang.org/x/tools/cmd/stress namely just runs the program in parallel loop) and instantly get the following crash.
Attaching my config just in case. I start qemu as:
qemu-system-x86_64 -net user,host=10.0.2.10,hostfwd=tcp::10022-:22 -net nic \ -no-reboot -display none -serial stdio -kernel arch/x86/boot/bzImage \ -fsdev local,id=fsdev0,path=/,security_model=none,readonly \ -device virtio-9p-pci,fsdev=fsdev0,mount_tag=/dev/root \ -enable-kvm -pidfile vm_pid -m 2G -numa node,nodeid=0,cpus=0-1 -numa node,nodeid=1,cpus=2-3 -smp sockets=2,cores=2,threads=1 \ -usb -usbdevice mouse -usbdevice tablet -soundhw all \ -append "console=ttyS0 debug oops=panic panic_on_warn=1 panic=-1 earlyprintk=serial slub_debug=UZ root=/dev/root rootfstype=9p rootflags=trans=virtio,version=9p2000.L,cache=loose init=/usr/local/google/home/dvyukov/bin/9p/init.sh"
sound dir is:
-bash-4.3# ls -lt /dev/snd/ total 0 crw------- 1 root 0 116, 20 Sep 6 14:03 hwC4D0 crw------- 1 root 0 116, 19 Sep 6 14:03 pcmC4D0c crw------- 1 root 0 116, 18 Sep 6 14:03 pcmC4D0p crw------- 1 root 0 116, 17 Sep 6 14:03 controlC4 crw------- 1 root 0 116, 16 Sep 6 14:03 pcmC3D0p crw------- 1 root 0 116, 15 Sep 6 14:03 controlC3 crw------- 1 root 0 116, 14 Sep 6 14:03 midiC2D3 crw------- 1 root 0 116, 13 Sep 6 14:03 midiC2D2 crw------- 1 root 0 116, 12 Sep 6 14:03 midiC2D1 crw------- 1 root 0 116, 11 Sep 6 14:03 midiC2D0 crw------- 1 root 0 116, 10 Sep 6 14:03 controlC2 crw------- 1 root 0 116, 9 Sep 6 14:03 pcmC1D1c crw------- 1 root 0 116, 8 Sep 6 14:03 pcmC1D1p crw------- 1 root 0 116, 7 Sep 6 14:03 pcmC1D0c crw------- 1 root 0 116, 6 Sep 6 14:03 pcmC1D0p crw------- 1 root 0 116, 5 Sep 6 14:03 controlC1 crw------- 1 root 0 116, 4 Sep 6 14:03 pcmC0D0c crw------- 1 root 0 116, 3 Sep 6 14:03 pcmC0D0p crw------- 1 root 0 116, 2 Sep 6 14:03 controlC0 crw------- 1 root 0 116, 1 Sep 6 14:03 seq crw------- 1 root 0 116, 33 Sep 6 14:03 timer
[ 134.435009] divide error: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN [ 134.435009] Modules linked in: [ 134.435009] CPU: 3 PID: 4965 Comm: a.out Not tainted 4.8.0-rc5-next-20160905+ #14 [ 134.435009] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 [ 134.435009] task: ffff880038b6e200 task.stack: ffff880036c48000 [ 134.435009] RIP: 0010:[<ffffffff858e147c>] [<ffffffff858e147c>] snd_hrtimer_callback+0x1bc/0x3c0 [ 134.435009] RSP: 0018:ffff88006d307dd8 EFLAGS: 00010006 [ 134.435009] RAX: 00000000002b5b0c RBX: ffff88006bb7d608 RCX: 0000000000000000 [ 134.435009] RDX: 0000000000000000 RSI: ffff88006bb7d620 RDI: ffffffff886b69a8 [ 134.435009] RBP: ffff88006d307e30 R08: 0000002066910785 R09: ffff88007fff70c8 [ 134.435009] R10: ffff88007fff70d8 R11: ffff88007fff70d0 R12: ffff880038ae3d00 [ 134.435009] R13: ffff880038ae3db4 R14: ffff880038ae3e30 R15: ffff88006bb7d600 [ 134.435009] FS: 00000000009f6940(0000) GS:ffff88006d300000(0000) knlGS:0000000000000000 [ 134.435009] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 134.435009] CR2: 000000002000ffb0 CR3: 000000006a816000 CR4: 00000000000006e0 [ 134.435009] Stack: [ 134.435009] 0000000000000000 ffff88006bb7d620 ffff880038ae3db8 00000000002b5b0c [ 134.435009] ffff88006bb7d660 0000000000000000 ffff88006bb7d608 0000000000000003 [ 134.435009] ffff88006d31b400 dffffc0000000000 0000000000000003 ffff88006d307f28 [ 134.447443] Call Trace: [ 134.447443] <IRQ> [ 134.447443] [<ffffffff81504425>] __hrtimer_run_queues+0x325/0xe70 [ 134.447443] [<ffffffff858e12c0>] ? snd_hrtimer_close+0x130/0x130 [ 134.447443] [<ffffffff81504100>] ? enqueue_hrtimer+0x3d0/0x3d0 [ 134.447443] [<ffffffff81506ddb>] hrtimer_interrupt+0x18b/0x420 [ 134.447443] [<ffffffff8126ceff>] local_apic_timer_interrupt+0x6f/0xe0 [ 134.450051] [<ffffffff86e1d216>] smp_apic_timer_interrupt+0x76/0xa0 [ 134.450051] [<ffffffff86e1c2cc>] apic_timer_interrupt+0x8c/0xa0 [ 134.450051] <EOI> [ 134.450051] [<ffffffff86e1a63e>] ? _raw_spin_unlock_irqrestore+0x5e/0xc0 [ 134.450051] [<ffffffff858daded>] snd_timer_start1+0xdd/0x740 [ 134.450051] [<ffffffff858db535>] snd_timer_continue+0x45/0x80 [ 134.450051] [<ffffffff858deca9>] snd_timer_user_ioctl+0xe99/0x2470 [ 134.450051] [<ffffffff858dde10>] ? snd_timer_user_params.isra.22+0xa30/0xa30 [ 134.450051] [<ffffffff8183bca0>] ? mem_cgroup_count_precharge_pte_range+0x530/0x530 [ 134.450051] [<ffffffff8183c03f>] ? get_mem_cgroup_from_mm+0x39f/0x4a0 [ 134.450051] [<ffffffff817129b4>] ? __lru_cache_add+0x174/0x210 [ 134.450051] [<ffffffff81715f49>] ? lru_cache_add+0xd9/0x1e0 [ 134.450051] [<ffffffff81791a30>] ? handle_mm_fault+0x28a0/0x34e0 [ 134.450051] [<ffffffff86e19c92>] ? _raw_spin_unlock+0x22/0x30 [ 134.450051] [<ffffffff8178fb40>] ? handle_mm_fault+0x9b0/0x34e0 [ 134.450051] [<ffffffff8178f2ca>] ? handle_mm_fault+0x13a/0x34e0 [ 134.450051] [<ffffffff8178f190>] ? __pmd_alloc+0x3f0/0x3f0 [ 134.450051] [<ffffffff818c902d>] ? __fd_install+0x24d/0x590 [ 134.450051] [<ffffffff818c8de0>] ? get_unused_fd_flags+0xd0/0xd0 [ 134.450051] [<ffffffff858dde10>] ? snd_timer_user_params.isra.22+0xa30/0xa30 [ 134.450051] [<ffffffff818a331c>] do_vfs_ioctl+0x18c/0x1080 [ 134.450051] [<ffffffff8129d19c>] ? __do_page_fault+0x2cc/0xbb0 [ 134.450051] [<ffffffff818a3190>] ? ioctl_preallocate+0x210/0x210 [ 134.450051] [<ffffffff8129d349>] ? __do_page_fault+0x479/0xbb0 [ 134.450051] [<ffffffff8148ef0a>] ? up_read+0x1a/0x40 [ 134.450051] [<ffffffff8129d068>] ? __do_page_fault+0x198/0xbb0 [ 134.450051] [<ffffffff82ad1dc9>] ? security_file_ioctl+0x89/0xb0 [ 134.450051] [<ffffffff818a429f>] SyS_ioctl+0x8f/0xc0 [ 134.450051] [<ffffffff86e1a8c0>] entry_SYSCALL_64_fastpath+0x23/0xc1 [ 134.450051] Code: 7b ad ce fb 8b 0d e5 f1 6f 05 48 0f af 4d d0 48 85 c9 0f 88 6a 01 00 00 48 89 4d a8 e8 5e ad ce fb 48 8b 45 c0 48 8b 4d a8 48 99 <48> f7 f9 48 01 45 d0 e8 48 ad ce fb 4c 89 fa 48 b8 00 00 00 00 [ 134.450051] RIP [<ffffffff858e147c>] snd_hrtimer_callback+0x1bc/0x3c0 [ 134.450051] RSP <ffff88006d307dd8> [ 134.450051] ---[ end trace 8614aafe29f5fee0 ]--- [ 134.450051] Kernel panic - not syncing: Fatal exception in interrupt [ 134.450051] Kernel Offset: disabled