bisecting fixing commit since e109a984cf380b4b80418b7477c970bfeb428325 building syzkaller on cf9c3a505dd23f7f4e391c0c24c9a9d3b9b26385 testing commit e109a984cf380b4b80418b7477c970bfeb428325 with gcc (GCC) 8.1.0 kernel signature: 96ec45853db5e1f0bfabbf958c7af352417e7746371d01831aad3180787f6fb7 all runs: crashed: INFO: task hung in do_exit testing current HEAD a083db76118d20d070794ecf79af17843406c3f6 testing commit a083db76118d20d070794ecf79af17843406c3f6 with gcc (GCC) 8.1.0 kernel signature: 0b14b6fe5968f21847dc894415c1f368a802838df378c1cc1bbb2a5d823c2b4c all runs: crashed: INFO: task hung in do_exit revisions tested: 2, total time: 30m13.940468094s (build: 17m22.05623391s, test: 11m52.252856915s) the crash still happens on HEAD commit msg: Linux 4.19.107 crash: INFO: task hung in do_exit IPv6: ADDRCONF(NETDEV_UP): vxcan1: link is not ready 8021q: adding VLAN 0 to HW filter on device batadv0 IPv6: ADDRCONF(NETDEV_UP): vxcan1: link is not ready 8021q: adding VLAN 0 to HW filter on device batadv0 INFO: task syz-executor.2:7127 blocked for more than 140 seconds. Not tainted 4.19.107-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.2 D28136 7127 7077 0x80000004 Call Trace: context_switch kernel/sched/core.c:2826 [inline] __schedule+0x78c/0x1c10 kernel/sched/core.c:3515 schedule+0x7f/0x1b0 kernel/sched/core.c:3559 __rwsem_down_read_failed_common kernel/locking/rwsem-xadd.c:292 [inline] rwsem_down_read_failed+0x21c/0x3e0 kernel/locking/rwsem-xadd.c:309 call_rwsem_down_read_failed+0x18/0x30 arch/x86/lib/rwsem.S:94 __down_read arch/x86/include/asm/rwsem.h:83 [inline] down_read+0x49/0xb0 kernel/locking/rwsem.c:26 exit_mm kernel/exit.c:512 [inline] do_exit+0x617/0x2d20 kernel/exit.c:867 do_group_exit+0xf4/0x2f0 kernel/exit.c:983 get_signal+0x313/0x1a00 kernel/signal.c:2583 do_signal+0x87/0x1960 arch/x86/kernel/signal.c:821 exit_to_usermode_loop+0x114/0x200 arch/x86/entry/common.c:163 prepare_exit_to_usermode arch/x86/entry/common.c:198 [inline] syscall_return_slowpath arch/x86/entry/common.c:271 [inline] do_syscall_64+0x413/0x4e0 arch/x86/entry/common.c:296 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x4592ca Code: Bad RIP value. RSP: 002b:00007ffe1f2c24c8 EFLAGS: 00000246 ORIG_RAX: 0000000000000009 RAX: fffffffffffffffc RBX: 0000000000000003 RCX: 00000000004592ca RDX: 0000000000000003 RSI: 0000000000021000 RDI: 0000000000000000 RBP: ffffffffffffffff R08: ffffffffffffffff R09: 0000000000000000 R10: 0000000000020022 R11: 0000000000000246 R12: 0000000000000000 R13: 0000000000021000 R14: 0000000000020022 R15: 0000000000000000 INFO: task syz-executor.2:7136 blocked for more than 140 seconds. Not tainted 4.19.107-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.2 D28616 7136 7077 0x80000004 Call Trace: context_switch kernel/sched/core.c:2826 [inline] __schedule+0x78c/0x1c10 kernel/sched/core.c:3515 schedule+0x7f/0x1b0 kernel/sched/core.c:3559 __rwsem_down_read_failed_common kernel/locking/rwsem-xadd.c:292 [inline] rwsem_down_read_failed+0x21c/0x3e0 kernel/locking/rwsem-xadd.c:309 call_rwsem_down_read_failed+0x18/0x30 arch/x86/lib/rwsem.S:94 __down_read arch/x86/include/asm/rwsem.h:83 [inline] down_read+0x49/0xb0 kernel/locking/rwsem.c:26 exit_mm kernel/exit.c:512 [inline] do_exit+0x617/0x2d20 kernel/exit.c:867 do_group_exit+0xf4/0x2f0 kernel/exit.c:983 get_signal+0x313/0x1a00 kernel/signal.c:2583 do_signal+0x87/0x1960 arch/x86/kernel/signal.c:821 exit_to_usermode_loop+0x114/0x200 arch/x86/entry/common.c:163 prepare_exit_to_usermode arch/x86/entry/common.c:198 [inline] syscall_return_slowpath arch/x86/entry/common.c:271 [inline] do_syscall_64+0x413/0x4e0 arch/x86/entry/common.c:296 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x459279 Code: Bad RIP value. RSP: 002b:00007fe6dd744c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000009 RAX: fffffffffffffffc RBX: 0000000000000006 RCX: 0000000000459279 RDX: 0000000001000000 RSI: 0000000000001000 RDI: 0000000020ffd000 RBP: 000000000075bfc0 R08: 0000000000000004 R09: 0000000000000000 R10: 0000000000000011 R11: 0000000000000246 R12: 00007fe6dd7456d4 R13: 00000000004c5567 R14: 00000000004d9918 R15: 00000000ffffffff Showing all locks held in the system: 1 lock held by khungtaskd/1036: #0: 000000005e9a90ba (rcu_read_lock){....}, at: debug_show_all_locks+0x5b/0x27a kernel/locking/lockdep.c:4438 1 lock held by rsyslogd/6833: #0: 000000002b82a7d7 (&f->f_pos_lock){+.+.}, at: __fdget_pos+0xa7/0xd0 fs/file.c:767 2 locks held by getty/6955: #0: 00000000633e1473 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x2d/0x40 drivers/tty/tty_ldsem.c:362 #1: 0000000034a4311a (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x1ee/0x1910 drivers/tty/n_tty.c:2154 2 locks held by getty/6956: #0: 00000000cd335a42 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x2d/0x40 drivers/tty/tty_ldsem.c:362 #1: 00000000fe499e94 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x1ee/0x1910 drivers/tty/n_tty.c:2154 2 locks held by getty/6957: #0: 00000000d6ad00a5 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x2d/0x40 drivers/tty/tty_ldsem.c:362 #1: 0000000038ddd384 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x1ee/0x1910 drivers/tty/n_tty.c:2154 2 locks held by getty/6958: #0: 0000000086353ef3 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x2d/0x40 drivers/tty/tty_ldsem.c:362 #1: 00000000d09b0bc0 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x1ee/0x1910 drivers/tty/n_tty.c:2154 2 locks held by getty/6959: #0: 000000006043454d (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x2d/0x40 drivers/tty/tty_ldsem.c:362 #1: 00000000c00d98b9 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x1ee/0x1910 drivers/tty/n_tty.c:2154 2 locks held by getty/6960: #0: 000000007828dfdd (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x2d/0x40 drivers/tty/tty_ldsem.c:362 #1: 0000000062d81521 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x1ee/0x1910 drivers/tty/n_tty.c:2154 2 locks held by getty/6961: #0: 0000000011addbcd (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x2d/0x40 drivers/tty/tty_ldsem.c:362 #1: 000000002b313271 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x1ee/0x1910 drivers/tty/n_tty.c:2154 1 lock held by syz-executor.2/7127: #0: 000000009b4cb2ac (&mm->mmap_sem){++++}, at: exit_mm kernel/exit.c:512 [inline] #0: 000000009b4cb2ac (&mm->mmap_sem){++++}, at: do_exit+0x617/0x2d20 kernel/exit.c:867 1 lock held by syz-executor.2/7128: 1 lock held by syz-executor.2/7136: #0: 000000009b4cb2ac (&mm->mmap_sem){++++}, at: exit_mm kernel/exit.c:512 [inline] #0: 000000009b4cb2ac (&mm->mmap_sem){++++}, at: do_exit+0x617/0x2d20 kernel/exit.c:867 ============================================= NMI backtrace for cpu 1 CPU: 1 PID: 1036 Comm: khungtaskd Not tainted 4.19.107-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+0x123/0x177 lib/dump_stack.c:118 nmi_cpu_backtrace.cold.4+0x3e/0x76 lib/nmi_backtrace.c:101 nmi_trigger_cpumask_backtrace+0xe6/0x11a 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:203 [inline] watchdog+0x5c3/0xb40 kernel/hung_task.c:287 kthread+0x324/0x3e0 kernel/kthread.c:246 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415 Sending NMI from CPU 1 to CPUs 0: NMI backtrace for cpu 0 CPU: 0 PID: 7 Comm: kworker/u4:0 Not tainted 4.19.107-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Workqueue: bat_events batadv_nc_worker RIP: 0010:mark_held_locks+0xc7/0x130 kernel/locking/lockdep.c:2805 Code: 03 83 e2 07 42 0f b6 04 38 38 d0 7f 04 84 c0 75 5e 0f b6 46 22 8b 55 d4 a8 03 0f 45 55 d0 a8 04 74 0c 4c 89 f7 e8 f9 eb ff ff <85> c0 74 1e 41 0f b6 45 00 83 c3 01 84 c0 74 04 3c 03 7e 40 41 39 RSP: 0018:ffff8880aa31fba0 EFLAGS: 00000082 RAX: 0000000000000001 RBX: 0000000000000001 RCX: 1ffff11015461951 RDX: 1ffffffff12c5108 RSI: ffff8880aa30ca68 RDI: ffffffff89628840 RBP: ffff8880aa31fbe0 R08: ffff8880aa30ca88 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: ffff8880aa30ca40 R13: ffffed1015461947 R14: ffff8880aa30c1c0 R15: dffffc0000000000 FS: 0000000000000000(0000) GS:ffff8880aea00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: ffffffffff600400 CR3: 000000008fd35000 CR4: 00000000001406f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: __trace_hardirqs_on_caller kernel/locking/lockdep.c:2834 [inline] lockdep_hardirqs_on+0x421/0x5c0 kernel/locking/lockdep.c:2879 trace_hardirqs_on+0x28/0x190 kernel/trace/trace_preemptirq.c:30 __local_bh_enable_ip+0x160/0x260 kernel/softirq.c:194 __raw_spin_unlock_bh include/linux/spinlock_api_smp.h:176 [inline] _raw_spin_unlock_bh+0x30/0x40 kernel/locking/spinlock.c:200 spin_unlock_bh include/linux/spinlock.h:374 [inline] batadv_nc_purge_paths+0x1d6/0x2f0 net/batman-adv/network-coding.c:482 batadv_nc_worker+0x1f3/0x630 net/batman-adv/network-coding.c:731 process_one_work+0x830/0x1670 kernel/workqueue.c:2153 worker_thread+0x85/0xb60 kernel/workqueue.c:2296 kthread+0x324/0x3e0 kernel/kthread.c:246 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415