Hello, syzbot found the following crash on: HEAD commit: 63623fd4 Merge tag 'for-linus' of git://git.kernel.org/pub.. git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=160452c3e00000 kernel config: https://syzkaller.appspot.com/x/.config?x=9833e26bab355358 dashboard link: https://syzkaller.appspot.com/bug?extid=0abbad99bee187cf63d4 compiler: gcc (GCC) 9.0.0 20181231 (experimental) Unfortunately, I don't have any reproducer for this crash yet. IMPORTANT: if you fix the bug, please add the following tag to the commit: Reported-by: syzbot+0abbad99bee187cf63d4@xxxxxxxxxxxxxxxxxxxxxxxxx INFO: task syz-executor.5:27890 blocked for more than 143 seconds. Not tainted 5.6.0-rc3-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.5 D28072 27890 11077 0x00000004 Call Trace: context_switch kernel/sched/core.c:3380 [inline] __schedule+0x934/0x1f90 kernel/sched/core.c:4080 schedule+0xdc/0x2b0 kernel/sched/core.c:4154 schedule_timeout+0x717/0xc50 kernel/time/timer.c:1871 do_wait_for_common kernel/sched/completion.c:83 [inline] __wait_for_common kernel/sched/completion.c:104 [inline] wait_for_common kernel/sched/completion.c:115 [inline] wait_for_completion+0x29c/0x440 kernel/sched/completion.c:136 rdma_destroy_id+0x680/0xdd0 drivers/infiniband/core/cma.c:1850 ucma_close+0x115/0x310 drivers/infiniband/core/ucma.c:1762 __fput+0x2ff/0x890 fs/file_table.c:280 ____fput+0x16/0x20 fs/file_table.c:313 task_work_run+0x145/0x1c0 kernel/task_work.c:113 tracehook_notify_resume include/linux/tracehook.h:188 [inline] exit_to_usermode_loop+0x316/0x380 arch/x86/entry/common.c:164 prepare_exit_to_usermode arch/x86/entry/common.c:195 [inline] syscall_return_slowpath arch/x86/entry/common.c:278 [inline] do_syscall_64+0x676/0x790 arch/x86/entry/common.c:304 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x416011 Code: 49 89 fc 48 83 e7 0f 48 81 cf f0 00 00 00 49 8d 43 04 4c 39 d0 0f 83 ec 00 00 00 41 88 38 90 49 c1 ec 04 48 39 d6 74 5d 49 83 <f9> 08 73 48 0f b6 02 48 89 cf 4c 89 c9 48 d3 e0 49 09 c4 90 48 8d RSP: 002b:00007ffe941054c0 EFLAGS: 00000293 ORIG_RAX: 0000000000000003 RAX: 0000000000000000 RBX: 0000000000000004 RCX: 0000000000416011 RDX: 0000001b2fe20000 RSI: 0000000000000000 RDI: 0000000000000003 RBP: 0000000000000001 R08: 00000000b9fbf2f5 R09: 00000000b9fbf2f9 R10: 00007ffe941055a0 R11: 0000000000000293 R12: 000000000076c920 R13: 000000000076c920 R14: 0000000000264fc6 R15: 000000000076bfcc Showing all locks held in the system: 2 locks held by kworker/u4:2/99: #0: ffff8880ae937558 (&rq->lock){-.-.}, at: newidle_balance+0xa28/0xe80 kernel/sched/fair.c:10219 #1: ffffc90001217dc0 ((work_completion)(&(&bat_priv->nc.work)->work)){+.+.}, at: process_one_work+0x917/0x17a0 kernel/workqueue.c:2239 1 lock held by khungtaskd/1135: #0: ffffffff89bac340 (rcu_read_lock){....}, at: debug_show_all_locks+0x5f/0x279 kernel/locking/lockdep.c:5333 2 locks held by rsyslogd/10884: #0: ffff88809b6e6ba0 (&f->f_pos_lock){+.+.}, at: __fdget_pos+0xee/0x110 fs/file.c:821 #1: ffffffff89ba13f8 (logbuf_lock){-.-.}, at: is_bpf_image_address+0x0/0x290 kernel/bpf/trampoline.c:86 2 locks held by getty/11006: #0: ffff888094516090 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:340 #1: ffffc9000184b2e0 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x220/0x1bf0 drivers/tty/n_tty.c:2156 2 locks held by getty/11007: #0: ffff888094714090 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:340 #1: ffffc9000185b2e0 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x220/0x1bf0 drivers/tty/n_tty.c:2156 2 locks held by getty/11008: #0: ffff8880906b4090 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:340 #1: ffffc9000186b2e0 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x220/0x1bf0 drivers/tty/n_tty.c:2156 2 locks held by getty/11009: #0: ffff888092b2c090 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:340 #1: ffffc9000187b2e0 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x220/0x1bf0 drivers/tty/n_tty.c:2156 2 locks held by getty/11010: #0: ffff88807bf93090 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:340 #1: ffffc900017e72e0 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x220/0x1bf0 drivers/tty/n_tty.c:2156 2 locks held by getty/11011: #0: ffff88808599f090 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:340 #1: ffffc9000188b2e0 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x220/0x1bf0 drivers/tty/n_tty.c:2156 2 locks held by getty/11012: #0: ffff8880a2abd090 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:340 #1: ffffc900017db2e0 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x220/0x1bf0 drivers/tty/n_tty.c:2156 ============================================= NMI backtrace for cpu 0 CPU: 0 PID: 1135 Comm: khungtaskd Not tainted 5.6.0-rc3-syzkaller #0 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+0x197/0x210 lib/dump_stack.c:118 nmi_cpu_backtrace.cold+0x70/0xb2 lib/nmi_backtrace.c:101 nmi_trigger_cpumask_backtrace+0x23b/0x28b lib/nmi_backtrace.c:62 arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38 trigger_all_cpu_backtrace include/linux/nmi.h:146 [inline] check_hung_uninterruptible_tasks kernel/hung_task.c:205 [inline] watchdog+0xb11/0x10c0 kernel/hung_task.c:289 kthread+0x361/0x430 kernel/kthread.c:255 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352 Sending NMI from CPU 0 to CPUs 1: NMI backtrace for cpu 1 CPU: 1 PID: 99 Comm: kworker/u4:2 Not tainted 5.6.0-rc3-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Workqueue: bat_events batadv_nc_worker RIP: 0010:__read_once_size include/linux/compiler.h:199 [inline] RIP: 0010:arch_atomic_read arch/x86/include/asm/atomic.h:31 [inline] RIP: 0010:atomic_read include/asm-generic/atomic-instrumented.h:27 [inline] RIP: 0010:rcu_dynticks_curr_cpu_in_eqs+0x7a/0xb0 kernel/rcu/tree.c:301 Code: ec e8 51 00 4c 89 e2 48 b8 00 00 00 00 00 fc ff df 48 c1 ea 03 0f b6 14 02 4c 89 e0 83 e0 07 83 c0 03 38 d0 7c 04 84 d2 75 17 <8b> 83 d8 00 00 00 48 83 c4 08 5b 41 5c 5d d1 e8 83 f0 01 83 e0 01 RSP: 0018:ffffc90001217c98 EFLAGS: 00000246 RAX: 0000000000000003 RBX: ffff8880ae938300 RCX: ffffffff816226d4 RDX: 0000000000000000 RSI: 0000000000000004 RDI: ffff8880ae9383d8 RBP: ffffc90001217cb0 R08: 1ffff11015d2707b R09: ffffed1015d2707c R10: ffffed1015d2707b R11: ffff8880ae9383db R12: ffff8880ae9383d8 R13: 0000000000000363 R14: 0000000000000000 R15: dffffc0000000000 FS: 0000000000000000(0000) GS:ffff8880ae900000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: ffffffffff600400 CR3: 000000009b725000 CR4: 00000000001426e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: rcu_is_watching+0x10/0x30 kernel/rcu/tree.c:919 rcu_read_unlock include/linux/rcupdate.h:651 [inline] batadv_nc_purge_orig_hash net/batman-adv/network-coding.c:411 [inline] batadv_nc_worker+0x480/0x760 net/batman-adv/network-coding.c:718 process_one_work+0xa05/0x17a0 kernel/workqueue.c:2264 worker_thread+0x98/0xe40 kernel/workqueue.c:2410 kthread+0x361/0x430 kernel/kthread.c:255 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352 --- This bug is generated by a bot. 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