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Date: Sun, 28 Oct 2018 10:44:00 -0700
From: Eric Dumazet <eric.dumazet@...il.com>
To: Dmitry Vyukov <dvyukov@...gle.com>,
syzbot <syzbot+6e682caa546b7c96c859@...kaller.appspotmail.com>,
Eric Dumazet <edumazet@...gle.com>
Cc: Alexei Starovoitov <ast@...nel.org>,
Daniel Borkmann <daniel@...earbox.net>,
David Miller <davem@...emloft.net>,
LKML <linux-kernel@...r.kernel.org>,
netdev <netdev@...r.kernel.org>, syzkaller-bugs@...glegroups.com
Subject: Re: WARNING in __debug_object_init (3)
On 10/28/2018 08:13 AM, Dmitry Vyukov wrote:
> On Sun, Oct 28, 2018 at 3:18 AM, syzbot
> <syzbot+6e682caa546b7c96c859@...kaller.appspotmail.com> wrote:
>> Hello,
>>
>> syzbot found the following crash on:
>>
>> HEAD commit: 8c60c36d0b8c Add linux-next specific files for 20181019
>> git tree: linux-next
>> console output: https://syzkaller.appspot.com/x/log.txt?x=100feec5400000
>> kernel config: https://syzkaller.appspot.com/x/.config?x=8b6d7c4c81535e89
>> dashboard link: https://syzkaller.appspot.com/bug?extid=6e682caa546b7c96c859
>> compiler: gcc (GCC) 8.0.1 20180413 (experimental)
>> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=13579abd400000
>> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=13654f6b400000
>>
>> IMPORTANT: if you fix the bug, please add the following tag to the commit:
>> Reported-by: syzbot+6e682caa546b7c96c859@...kaller.appspotmail.com
>
> +Eric knows what's wrong here. Something about "bpf: add tests for
> direct packet access from CGROUP_SKB" commit. Was is amended to fix a
> bug?
>
I know little.
It seems that this linux-next tree contains a (buggy) pre-version of
this commit :
commit 2cb494a36c98279c5c6ce8e99cf9776f15449ade
Author: Song Liu <songliubraving@...com>
Date: Fri Oct 19 09:57:58 2018 -0700
bpf: add tests for direct packet access from CGROUP_SKB
Tests are added to make sure CGROUP_SKB cannot access:
tc_classid, data_meta, flow_keys
and can read and write:
mark, prority, and cb[0-4]
and can read other fields.
To make selftest with skb->sk work, a dummy sk is added in
bpf_prog_test_run_skb().
Signed-off-by: Song Liu <songliubraving@...com>
Signed-off-by: Alexei Starovoitov <ast@...nel.org>
Maybe bpf maintainers chose to pre-submit a buggy patch and rebased their tree.
The buggy patch in linux-next was :
commit 75079847e9d05d4cc1b7e09b29e22cbc8318a6b7
Author: Song Liu <songliubraving@...com>
Date: Thu Oct 18 09:06:49 2018 -0700
bpf: add tests for direct packet access from CGROUP_SKB
Tests are added to make sure CGROUP_SKB cannot access:
tc_classid, data_meta, flow_keys
and can read and write:
mark, prority, and cb[0-4]
and can read other fields.
To make selftest with skb->sk work, a dummy sk is added in
bpf_prog_test_run_skb().
Signed-off-by: Song Liu <songliubraving@...com>
Signed-off-by: Alexei Starovoitov <ast@...nel.org>
>
>> ODEBUG: object 0000000015e9012c is on stack 00000000115bcb67, but NOT
>> annotated.
>> WARNING: CPU: 0 PID: 5594 at lib/debugobjects.c:369 debug_object_is_on_stack
>> lib/debugobjects.c:363 [inline]
>> WARNING: CPU: 0 PID: 5594 at lib/debugobjects.c:369
>> __debug_object_init.cold.14+0x51/0xdf lib/debugobjects.c:395
>> Kernel panic - not syncing: panic_on_warn set ...
>> CPU: 0 PID: 5594 Comm: syz-executor740 Not tainted 4.19.0-rc8-next-20181019+
>> #98
>> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
>> Google 01/01/2011
>> Call Trace:
>> __dump_stack lib/dump_stack.c:77 [inline]
>> dump_stack+0x244/0x39d lib/dump_stack.c:113
>> panic+0x2ad/0x55c kernel/panic.c:188
>> __warn.cold.8+0x20/0x45 kernel/panic.c:540
>> report_bug+0x254/0x2d0 lib/bug.c:186
>> fixup_bug arch/x86/kernel/traps.c:178 [inline]
>> do_error_trap+0x11b/0x200 arch/x86/kernel/traps.c:271
>> do_invalid_op+0x36/0x40 arch/x86/kernel/traps.c:290
>> invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:969
>> RIP: 0010:debug_object_is_on_stack lib/debugobjects.c:363 [inline]
>> RIP: 0010:__debug_object_init.cold.14+0x51/0xdf lib/debugobjects.c:395
>> Code: ea 03 80 3c 02 00 75 7c 49 8b 54 24 18 48 89 de 48 c7 c7 c0 f1 40 88
>> 4c 89 85 d0 fd ff ff e8 09 8c d1 fd 4c 8b 85 d0 fd ff ff <0f> 0b e9 09 d6 ff
>> ff 41 83 c4 01 b8 ff ff 37 00 44 89 25 b7 4e 66
>> RSP: 0018:ffff8801bb387308 EFLAGS: 00010086
>> RAX: 0000000000000050 RBX: ffff8801bb387af8 RCX: 0000000000000000
>> RDX: 0000000000000000 RSI: ffffffff816585a5 RDI: 0000000000000005
>> RBP: ffff8801bb387560 R08: ffff8801cb208a20 R09: ffffed003b5c5008
>> R10: ffffed003b5c5008 R11: ffff8801dae28047 R12: ffff8801d82ea300
>> R13: 0000000000069700 R14: ffff8801d82ea300 R15: ffff8801cb208a10
>> debug_object_init+0x16/0x20 lib/debugobjects.c:432
>> debug_timer_init kernel/time/timer.c:704 [inline]
>> debug_init kernel/time/timer.c:757 [inline]
>> init_timer_key+0xa9/0x480 kernel/time/timer.c:806
>> sock_init_data+0xe1/0xdc0 net/core/sock.c:2696
>> bpf_prog_test_run_skb+0x255/0xc40 net/bpf/test_run.c:144
>> bpf_prog_test_run+0x130/0x1a0 kernel/bpf/syscall.c:1790
>> __do_sys_bpf kernel/bpf/syscall.c:2427 [inline]
>> __se_sys_bpf kernel/bpf/syscall.c:2371 [inline]
>> __x64_sys_bpf+0x3d8/0x510 kernel/bpf/syscall.c:2371
>> do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
>> entry_SYSCALL_64_after_hwframe+0x49/0xbe
>> RIP: 0033:0x440259
>> Code: 18 89 d0 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 48 89 f8 48 89 f7
>> 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff
>> 0f 83 fb 13 fc ff c3 66 2e 0f 1f 84 00 00 00 00
>> RSP: 002b:00007ffc212cf818 EFLAGS: 00000213 ORIG_RAX: 0000000000000141
>> RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 0000000000440259
>> RDX: 0000000000000028 RSI: 0000000020000080 RDI: 000000000000000a
>> RBP: 00000000006ca018 R08: 0000000000000000 R09: 00000000004002c8
>> R10: 0000000000000000 R11: 0000000000000213 R12: 0000000000401ae0
>> R13: 0000000000401b70 R14: 0000000000000000 R15: 0000000000000000
>>
>> ======================================================
>> WARNING: possible circular locking dependency detected
>> 4.19.0-rc8-next-20181019+ #98 Not tainted
>> ------------------------------------------------------
>> syz-executor740/5594 is trying to acquire lock:
>> 00000000688fcc6b ((console_sem).lock){-.-.}, at: down_trylock+0x13/0x70
>> kernel/locking/semaphore.c:136
>>
>> but task is already holding lock:
>> 00000000505ead1b (&obj_hash[i].lock){-.-.}, at:
>> __debug_object_init+0x127/0x1290 lib/debugobjects.c:384
>>
>> which lock already depends on the new lock.
>>
>>
>> the existing dependency chain (in reverse order) is:
>>
>> -> #3 (&obj_hash[i].lock){-.-.}:
>> __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
>> _raw_spin_lock_irqsave+0x99/0xd0 kernel/locking/spinlock.c:152
>> __debug_object_init+0x127/0x1290 lib/debugobjects.c:384
>> debug_object_init+0x16/0x20 lib/debugobjects.c:432
>> debug_hrtimer_init kernel/time/hrtimer.c:410 [inline]
>> debug_init kernel/time/hrtimer.c:458 [inline]
>> hrtimer_init+0x97/0x490 kernel/time/hrtimer.c:1308
>> init_dl_task_timer+0x1b/0x50 kernel/sched/deadline.c:1057
>> __sched_fork+0x2ae/0x590 kernel/sched/core.c:2166
>> init_idle+0x75/0x740 kernel/sched/core.c:5382
>> sched_init+0xb33/0xc02 kernel/sched/core.c:6065
>> start_kernel+0x4be/0xa2b init/main.c:608
>> x86_64_start_reservations+0x2e/0x30 arch/x86/kernel/head64.c:472
>> x86_64_start_kernel+0x76/0x79 arch/x86/kernel/head64.c:451
>> secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:243
>>
>> -> #2 (&rq->lock){-.-.}:
>> __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
>> _raw_spin_lock+0x2d/0x40 kernel/locking/spinlock.c:144
>> rq_lock kernel/sched/sched.h:1127 [inline]
>> task_fork_fair+0xb0/0x6d0 kernel/sched/fair.c:9768
>> sched_fork+0x443/0xba0 kernel/sched/core.c:2359
>> copy_process+0x2585/0x8770 kernel/fork.c:1887
>> _do_fork+0x1cb/0x11c0 kernel/fork.c:2216
>> kernel_thread+0x34/0x40 kernel/fork.c:2275
>> rest_init+0x28/0x372 init/main.c:409
>> arch_call_rest_init+0xe/0x1b
>> start_kernel+0x9f0/0xa2b init/main.c:745
>> x86_64_start_reservations+0x2e/0x30 arch/x86/kernel/head64.c:472
>> x86_64_start_kernel+0x76/0x79 arch/x86/kernel/head64.c:451
>> secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:243
>>
>> -> #1 (&p->pi_lock){-.-.}:
>> __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
>> _raw_spin_lock_irqsave+0x99/0xd0 kernel/locking/spinlock.c:152
>> try_to_wake_up+0xd2/0x12e0 kernel/sched/core.c:1965
>> wake_up_process+0x10/0x20 kernel/sched/core.c:2129
>> __up.isra.1+0x1c0/0x2a0 kernel/locking/semaphore.c:262
>> up+0x13c/0x1c0 kernel/locking/semaphore.c:187
>> __up_console_sem+0xbe/0x1b0 kernel/printk/printk.c:236
>> console_unlock+0x80c/0x1190 kernel/printk/printk.c:2432
>> vprintk_emit+0x391/0x990 kernel/printk/printk.c:1922
>> vprintk_default+0x28/0x30 kernel/printk/printk.c:1964
>> vprintk_func+0x7e/0x181 kernel/printk/printk_safe.c:398
>> printk+0xa7/0xcf kernel/printk/printk.c:1997
>> check_stack_usage kernel/exit.c:755 [inline]
>> do_exit.cold.18+0x57/0x16f kernel/exit.c:916
>> do_group_exit+0x177/0x440 kernel/exit.c:970
>> __do_sys_exit_group kernel/exit.c:981 [inline]
>> __se_sys_exit_group kernel/exit.c:979 [inline]
>> __x64_sys_exit_group+0x3e/0x50 kernel/exit.c:979
>> do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
>> entry_SYSCALL_64_after_hwframe+0x49/0xbe
>>
>> -> #0 ((console_sem).lock){-.-.}:
>> lock_acquire+0x1ed/0x520 kernel/locking/lockdep.c:3844
>> __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
>> _raw_spin_lock_irqsave+0x99/0xd0 kernel/locking/spinlock.c:152
>> down_trylock+0x13/0x70 kernel/locking/semaphore.c:136
>> __down_trylock_console_sem+0xae/0x1f0 kernel/printk/printk.c:219
>> console_trylock+0x15/0xa0 kernel/printk/printk.c:2247
>> console_trylock_spinning kernel/printk/printk.c:1653 [inline]
>> vprintk_emit+0x372/0x990 kernel/printk/printk.c:1921
>> vprintk_default+0x28/0x30 kernel/printk/printk.c:1964
>> vprintk_func+0x7e/0x181 kernel/printk/printk_safe.c:398
>> printk+0xa7/0xcf kernel/printk/printk.c:1997
>> debug_object_is_on_stack lib/debugobjects.c:363 [inline]
>> __debug_object_init.cold.14+0x4a/0xdf lib/debugobjects.c:395
>> debug_object_init+0x16/0x20 lib/debugobjects.c:432
>> debug_timer_init kernel/time/timer.c:704 [inline]
>> debug_init kernel/time/timer.c:757 [inline]
>> init_timer_key+0xa9/0x480 kernel/time/timer.c:806
>> sock_init_data+0xe1/0xdc0 net/core/sock.c:2696
>> bpf_prog_test_run_skb+0x255/0xc40 net/bpf/test_run.c:144
>> bpf_prog_test_run+0x130/0x1a0 kernel/bpf/syscall.c:1790
>> __do_sys_bpf kernel/bpf/syscall.c:2427 [inline]
>> __se_sys_bpf kernel/bpf/syscall.c:2371 [inline]
>> __x64_sys_bpf+0x3d8/0x510 kernel/bpf/syscall.c:2371
>> do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
>> entry_SYSCALL_64_after_hwframe+0x49/0xbe
>>
>> other info that might help us debug this:
>>
>> Chain exists of:
>> (console_sem).lock --> &rq->lock --> &obj_hash[i].lock
>>
>> Possible unsafe locking scenario:
>>
>> CPU0 CPU1
>> ---- ----
>> lock(&obj_hash[i].lock);
>> lock(&rq->lock);
>> lock(&obj_hash[i].lock);
>> lock((console_sem).lock);
>>
>> *** DEADLOCK ***
>>
>> 1 lock held by syz-executor740/5594:
>> #0: 00000000505ead1b (&obj_hash[i].lock){-.-.}, at:
>> __debug_object_init+0x127/0x1290 lib/debugobjects.c:384
>>
>> stack backtrace:
>> CPU: 0 PID: 5594 Comm: syz-executor740 Not tainted 4.19.0-rc8-next-20181019+
>> #98
>> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
>> Google 01/01/2011
>> Call Trace:
>> __dump_stack lib/dump_stack.c:77 [inline]
>> dump_stack+0x244/0x39d lib/dump_stack.c:113
>> print_circular_bug.isra.35.cold.54+0x1bd/0x27d
>> kernel/locking/lockdep.c:1221
>> check_prev_add kernel/locking/lockdep.c:1863 [inline]
>> check_prevs_add kernel/locking/lockdep.c:1976 [inline]
>> validate_chain kernel/locking/lockdep.c:2347 [inline]
>> __lock_acquire+0x3399/0x4c20 kernel/locking/lockdep.c:3341
>> lock_acquire+0x1ed/0x520 kernel/locking/lockdep.c:3844
>> __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
>> _raw_spin_lock_irqsave+0x99/0xd0 kernel/locking/spinlock.c:152
>> down_trylock+0x13/0x70 kernel/locking/semaphore.c:136
>> __down_trylock_console_sem+0xae/0x1f0 kernel/printk/printk.c:219
>> console_trylock+0x15/0xa0 kernel/printk/printk.c:2247
>> console_trylock_spinning kernel/printk/printk.c:1653 [inline]
>> vprintk_emit+0x372/0x990 kernel/printk/printk.c:1921
>> vprintk_default+0x28/0x30 kernel/printk/printk.c:1964
>> vprintk_func+0x7e/0x181 kernel/printk/printk_safe.c:398
>> printk+0xa7/0xcf kernel/printk/printk.c:1997
>> debug_object_is_on_stack lib/debugobjects.c:363 [inline]
>> __debug_object_init.cold.14+0x4a/0xdf lib/debugobjects.c:395
>> debug_object_init+0x16/0x20 lib/debugobjects.c:432
>> debug_timer_init kernel/time/timer.c:704 [inline]
>> debug_init kernel/time/timer.c:757 [inline]
>> init_timer_key+0xa9/0x480 kernel/time/timer.c:806
>> sock_init_data+0xe1/0xdc0 net/core/sock.c:2696
>> bpf_prog_test_run_skb+0x255/0xc40 net/bpf/test_run.c:144
>> bpf_prog_test_run+0x130/0x1a0 kernel/bpf/syscall.c:1790
>> __do_sys_bpf kernel/bpf/syscall.c:2427 [inline]
>> __se_sys_bpf kernel/bpf/syscall.c:2371 [inline]
>> __x64_sys_bpf+0x3d8/0x510 kernel/bpf/syscall.c:2371
>> do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
>> entry_SYSCALL_64_after_hwframe+0x49/0xbe
>> RIP: 0033:0x440259
>> Code: 18 89 d0 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 48 89 f8 48 89 f7
>> 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff
>> 0f 83 fb 13 fc ff c3 66 2e 0f 1f 84 00 00 00 00
>> RSP: 002b:00007ffc212cf818 EFLAGS: 00000213 ORIG_RAX: 0000000000000141
>> RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 0000000000440259
>> RDX: 0000000000000028 RSI: 0000000020000080 RDI: 000000000000000a
>> RBP: 00000000006ca018 R08: 0000000000000000 R09: 00000000004002c8
>> R10: 0000000000000000 R11: 0000000000000213 R12: 0000000000401ae0
>> R13: 0000000000401b70 R14: 0000000000000000 R15: 0000000000000000
>> Kernel Offset: disabled
>> Rebooting in 86400 seconds..
>>
>>
>> ---
>> This bug is generated by a bot. It may contain errors.
>> See https://goo.gl/tpsmEJ for more information about syzbot.
>> syzbot engineers can be reached at syzkaller@...glegroups.com.
>>
>> syzbot will keep track of this bug report. See:
>> https://goo.gl/tpsmEJ#bug-status-tracking for how to communicate with
>> syzbot.
>> syzbot can test patches for this bug, for details see:
>> https://goo.gl/tpsmEJ#testing-patches
>>
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