On Thu, Oct 1, 2020 at 12:35 PM syzbot syzbot+69904c3b4a09e8fa2e1b@syzkaller.appspotmail.com wrote:

Hello,

syzbot found the following issue on:

HEAD commit: fffe3ae0 Merge tag 'for-linus-hmm' of git://git.kernel.org.. git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=17e03342900000 kernel config: https://syzkaller.appspot.com/x/.config?x=226c7a97d80bec54 dashboard link: https://syzkaller.appspot.com/bug?extid=69904c3b4a09e8fa2e1b compiler: clang version 10.0.0 (https://github.com/llvm/llvm-project/ c2443155a0fb245c8f17f2c1c72b6ea391e86e81)

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+69904c3b4a09e8fa2e1b@syzkaller.appspotmail.com

+batadv maintainers

May be related to: KMSAN: uninit-value in batadv_nc_worker https://syzkaller.appspot.com/bug?extid=da9194708de785081f11

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks: rcu: 0-...!: (1 GPs behind) idle=22e/1/0x4000000000000000 softirq=85361/85365 fqs=8 (detected by 1, t=10502 jiffies, g=114061, q=1511) Sending NMI from CPU 1 to CPUs 0: NMI backtrace for cpu 0 CPU: 0 PID: 194 Comm: kworker/u4:4 Not tainted 5.8.0-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Workqueue: bat_events batadv_nc_worker RIP: 0010:arch_local_save_flags arch/x86/include/asm/paravirt.h:765 [inline] RIP: 0010:arch_local_irq_save arch/x86/include/asm/paravirt.h:787 [inline] RIP: 0010:__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:108 [inline] RIP: 0010:_raw_spin_lock_irqsave+0x3c/0xc0 kernel/locking/spinlock.c:159 Code: 03 49 bf 00 00 00 00 00 fc ff df 42 80 3c 38 00 74 0c 48 c7 c7 b0 d5 4b 89 e8 a0 97 92 f9 48 83 3d 38 61 2a 01 00 74 79 9c 58 <0f> 1f 44 00 00 49 89 c6 48 c7 c0 c0 d5 4b 89 48 c1 e8 03 42 80 3c RSP: 0018:ffffc90000007d40 EFLAGS: 00000082 RAX: 0000000000000082 RBX: ffffffff8ba182b8 RCX: 000000000000d6e0 RDX: 0000000080010001 RSI: ffffffff894eec80 RDI: ffffffff8ba182b8 RBP: ffffffff894eec80 R08: ffffffff816542f4 R09: fffff52000000fb0 R10: fffff52000000fb0 R11: 0000000000000000 R12: dffffc0000000000 R13: 1ffff11015d04ed2 R14: dffffc0000000000 R15: dffffc0000000000 FS: 0000000000000000(0000) GS:ffff8880ae800000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00000000004ddaf0 CR3: 0000000090ca1000 CR4: 00000000001506f0 DR0: 0000000020000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000600 Call Trace:

<IRQ> debug_object_activate+0x62/0x5f0 lib/debugobjects.c:636 debug_hrtimer_activate kernel/time/hrtimer.c:416 [inline] debug_activate kernel/time/hrtimer.c:476 [inline] enqueue_hrtimer kernel/time/hrtimer.c:965 [inline] __run_hrtimer kernel/time/hrtimer.c:1537 [inline] __hrtimer_run_queues+0x510/0x930 kernel/time/hrtimer.c:1584 hrtimer_interrupt+0x373/0xd60 kernel/time/hrtimer.c:1646 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1080 [inline] __sysvec_apic_timer_interrupt+0xf0/0x260 arch/x86/kernel/apic/apic.c:1097 asm_call_on_stack+0xf/0x20 arch/x86/entry/entry_64.S:706 </IRQ> __run_on_irqstack arch/x86/include/asm/irq_stack.h:22 [inline] run_on_irqstack_cond arch/x86/include/asm/irq_stack.h:48 [inline] sysvec_apic_timer_interrupt+0x94/0xf0 arch/x86/kernel/apic/apic.c:1091 asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:581 RIP: 0010:arch_local_irq_restore arch/x86/include/asm/paravirt.h:770 [inline] RIP: 0010:lock_release+0x3c4/0x750 kernel/locking/lockdep.c:5026 Code: 48 c1 e8 03 42 80 3c 28 00 74 0c 48 c7 c7 b8 d5 4b 89 e8 3f 0b 5a 00 48 83 3d df d4 f1 07 00 0f 84 5c 03 00 00 4c 89 e7 57 9d <0f> 1f 44 00 00 65 48 8b 04 25 28 00 00 00 48 3b 44 24 50 0f 85 40 RSP: 0018:ffffc90001037bf8 EFLAGS: 00000282 RAX: 1ffffffff1297ab7 RBX: 1ffff110151d2949 RCX: ffff8880a8e94180 RDX: ffff8880a8e94a48 RSI: ffffffff894ea290 RDI: 0000000000000282 RBP: 9644b5a36c253f0c R08: dffffc0000000000 R09: fffffbfff131b08e R10: fffffbfff131b08e R11: 0000000000000000 R12: 0000000000000282 R13: dffffc0000000000 R14: dffffc0000000000 R15: ffff8880a8e94a4c rcu_read_unlock include/linux/rcupdate.h:688 [inline] batadv_nc_purge_orig_hash net/batman-adv/network-coding.c:411 [inline] batadv_nc_worker+0x261/0x5c0 net/batman-adv/network-coding.c:718 process_one_work+0x789/0xfc0 kernel/workqueue.c:2269 worker_thread+0xaa4/0x1460 kernel/workqueue.c:2415 kthread+0x37e/0x3a0 drivers/block/aoe/aoecmd.c:1234 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294 rcu: rcu_preempt kthread starved for 10486 jiffies! g114061 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402 ->cpu=1 rcu: Unless rcu_preempt kthread gets sufficient CPU time, OOM is now expected behavior. rcu: RCU grace-period kthread stack dump: rcu_preempt I28608 10 2 0x00004000 Call Trace: context_switch kernel/sched/core.c:3778 [inline] __schedule+0x979/0xce0 kernel/sched/core.c:4527

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