bisecting fixing commit since bfb9e5c03076a446b1f4f6a523ddc8d723c907a6 building syzkaller on 79b211f74b08737aeb4934c6ff69a263b3c38013 testing commit bfb9e5c03076a446b1f4f6a523ddc8d723c907a6 with gcc (GCC) 8.1.0 kernel signature: ab58466a5a3a4b973eb210cb9c6fbe9290f7737507cbb4374388480835139fd2 run #0: crashed: INFO: task hung in pipe_write run #1: crashed: INFO: task hung in pipe_write run #2: crashed: INFO: task hung in pipe_write run #3: crashed: INFO: task hung in pipe_write run #4: crashed: INFO: task hung in pipe_write run #5: crashed: INFO: task hung in pipe_write run #6: crashed: INFO: task hung in pipe_write run #7: crashed: INFO: task hung in pipe_write run #8: crashed: INFO: task hung in pipe_read run #9: OK testing current HEAD 98db2bf27b9ed2d5ed0b6c9c8a4bfcb127a19796 testing commit 98db2bf27b9ed2d5ed0b6c9c8a4bfcb127a19796 with gcc (GCC) 8.1.0 kernel signature: 01744428e833128cf0e07e702bfa402a0067254990fd3bc638006ac1d09cb37f run #0: crashed: INFO: task hung in pipe_write run #1: crashed: INFO: task hung in pipe_write run #2: crashed: INFO: task hung in pipe_write run #3: crashed: INFO: task hung in pipe_read run #4: crashed: INFO: task hung in pipe_write run #5: crashed: INFO: task hung in pipe_write run #6: crashed: INFO: task hung in pipe_read run #7: crashed: INFO: task hung in pipe_write run #8: crashed: INFO: task hung in pipe_write run #9: crashed: INFO: task hung in pipe_read revisions tested: 2, total time: 36m33.342887496s (build: 16m47.370457066s, test: 19m14.482440804s) the crash still happens on HEAD commit msg: Linux 4.14.171 crash: INFO: task hung in pipe_read INFO: task syz-execprog:16754 blocked for more than 140 seconds. Not tainted 4.14.171-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-execprog D28488 16754 6941 0x00000000 Call Trace: context_switch kernel/sched/core.c:2808 [inline] __schedule+0x780/0x1d20 kernel/sched/core.c:3384 schedule+0x7f/0x1b0 kernel/sched/core.c:3428 schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3486 __mutex_lock_common kernel/locking/mutex.c:833 [inline] __mutex_lock+0xabc/0x14c0 kernel/locking/mutex.c:893 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908 __pipe_lock fs/pipe.c:88 [inline] pipe_read+0xaa/0x7b0 fs/pipe.c:279 call_read_iter include/linux/fs.h:1771 [inline] new_sync_read fs/read_write.c:401 [inline] __vfs_read+0x410/0x840 fs/read_write.c:413 vfs_read+0xf5/0x300 fs/read_write.c:447 SYSC_read fs/read_write.c:574 [inline] SyS_read+0x100/0x250 fs/read_write.c:567 do_syscall_64+0x1c7/0x5b0 arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x42/0xb7 RIP: 0033:0x47ea10 RSP: 002b:000000c4201a3588 EFLAGS: 00000212 ORIG_RAX: 0000000000000000 RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 000000000047ea10 RDX: 0000000000010000 RSI: 000000c42026e000 RDI: 0000000000000019 RBP: 000000c4201a35e0 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000212 R12: 000000c42002cf50 R13: 0000000000000001 R14: 000000c4200d57a0 R15: 0000000000000001 INFO: task syz-executor.0:9637 blocked for more than 140 seconds. Not tainted 4.14.171-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.0 D29608 9637 6963 0x00000000 Call Trace: context_switch kernel/sched/core.c:2808 [inline] __schedule+0x780/0x1d20 kernel/sched/core.c:3384 schedule+0x7f/0x1b0 kernel/sched/core.c:3428 schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3486 __mutex_lock_common kernel/locking/mutex.c:833 [inline] __mutex_lock+0xabc/0x14c0 kernel/locking/mutex.c:893 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908 __pipe_lock fs/pipe.c:88 [inline] pipe_write+0xa6/0xd10 fs/pipe.c:385 call_write_iter include/linux/fs.h:1777 [inline] new_sync_write fs/read_write.c:469 [inline] __vfs_write+0x413/0x840 fs/read_write.c:482 vfs_write+0x150/0x4f0 fs/read_write.c:544 SYSC_write fs/read_write.c:590 [inline] SyS_write+0x100/0x250 fs/read_write.c:582 do_syscall_64+0x1c7/0x5b0 arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x42/0xb7 RIP: 0033:0x45a919 RSP: 002b:00007fa2f8766c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 000000000045a919 RDX: 000000010000000d RSI: 0000000020000000 RDI: 0000000000000000 RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00007fa2f87676d4 R13: 00000000004cbe11 R14: 00000000004e5be8 R15: 00000000ffffffff Showing all locks held in the system: 1 lock held by khungtaskd/1044: #0: (tasklist_lock){.+.+}, at: [] debug_show_all_locks+0x79/0x218 kernel/locking/lockdep.c:4544 2 locks held by getty/6845: #0: (&tty->ldisc_sem){++++}, at: [] ldsem_down_read+0x2d/0x40 drivers/tty/tty_ldsem.c:376 #1: (&ldata->atomic_read_lock){+.+.}, at: [] n_tty_read+0x1e6/0x18f0 drivers/tty/n_tty.c:2156 2 locks held by getty/6846: #0: (&tty->ldisc_sem){++++}, at: [] ldsem_down_read+0x2d/0x40 drivers/tty/tty_ldsem.c:376 #1: (&ldata->atomic_read_lock){+.+.}, at: [] n_tty_read+0x1e6/0x18f0 drivers/tty/n_tty.c:2156 2 locks held by getty/6847: #0: (&tty->ldisc_sem){++++}, at: [] ldsem_down_read+0x2d/0x40 drivers/tty/tty_ldsem.c:376 #1: (&ldata->atomic_read_lock){+.+.}, at: [] n_tty_read+0x1e6/0x18f0 drivers/tty/n_tty.c:2156 2 locks held by getty/6848: #0: (&tty->ldisc_sem){++++}, at: [] ldsem_down_read+0x2d/0x40 drivers/tty/tty_ldsem.c:376 #1: (&ldata->atomic_read_lock){+.+.}, at: [] n_tty_read+0x1e6/0x18f0 drivers/tty/n_tty.c:2156 2 locks held by getty/6849: #0: (&tty->ldisc_sem){++++}, at: [] ldsem_down_read+0x2d/0x40 drivers/tty/tty_ldsem.c:376 #1: (&ldata->atomic_read_lock){+.+.}, at: [] n_tty_read+0x1e6/0x18f0 drivers/tty/n_tty.c:2156 2 locks held by getty/6850: #0: (&tty->ldisc_sem){++++}, at: [] ldsem_down_read+0x2d/0x40 drivers/tty/tty_ldsem.c:376 #1: (&ldata->atomic_read_lock){+.+.}, at: [] n_tty_read+0x1e6/0x18f0 drivers/tty/n_tty.c:2156 2 locks held by getty/6851: #0: (&tty->ldisc_sem){++++}, at: [] ldsem_down_read+0x2d/0x40 drivers/tty/tty_ldsem.c:376 #1: (&ldata->atomic_read_lock){+.+.}, at: [] n_tty_read+0x1e6/0x18f0 drivers/tty/n_tty.c:2156 1 lock held by syz-execprog/16754: #0: (&pipe->mutex/1){+.+.}, at: [] __pipe_lock fs/pipe.c:88 [inline] #0: (&pipe->mutex/1){+.+.}, at: [] pipe_read+0xaa/0x7b0 fs/pipe.c:279 1 lock held by syz-executor.4/20732: #0: (&pipe->mutex/1){+.+.}, at: [] pipe_lock_nested fs/pipe.c:67 [inline] #0: (&pipe->mutex/1){+.+.}, at: [] pipe_lock fs/pipe.c:75 [inline] #0: (&pipe->mutex/1){+.+.}, at: [] pipe_wait+0x16c/0x190 fs/pipe.c:123 1 lock held by syz-executor.0/20889: #0: (&pipe->mutex/1){+.+.}, at: [] pipe_lock_nested fs/pipe.c:67 [inline] #0: (&pipe->mutex/1){+.+.}, at: [] pipe_lock fs/pipe.c:75 [inline] #0: (&pipe->mutex/1){+.+.}, at: [] pipe_wait+0x16c/0x190 fs/pipe.c:123 1 lock held by syz-executor.0/9637: #0: (&pipe->mutex/1){+.+.}, at: [] __pipe_lock fs/pipe.c:88 [inline] #0: (&pipe->mutex/1){+.+.}, at: [] pipe_write+0xa6/0xd10 fs/pipe.c:385 1 lock held by syz-executor.1/20363: #0: (&pipe->mutex/1){+.+.}, at: [] pipe_lock_nested fs/pipe.c:67 [inline] #0: (&pipe->mutex/1){+.+.}, at: [] pipe_lock fs/pipe.c:75 [inline] #0: (&pipe->mutex/1){+.+.}, at: [] pipe_wait+0x16c/0x190 fs/pipe.c:123 1 lock held by syz-executor.0/20364: #0: (&pipe->mutex/1){+.+.}, at: [] __pipe_lock fs/pipe.c:88 [inline] #0: (&pipe->mutex/1){+.+.}, at: [] pipe_write+0xa6/0xd10 fs/pipe.c:385 1 lock held by syz-executor.2/5458: #0: (&pipe->mutex/1){+.+.}, at: [] pipe_lock_nested fs/pipe.c:67 [inline] #0: (&pipe->mutex/1){+.+.}, at: [] pipe_lock fs/pipe.c:75 [inline] #0: (&pipe->mutex/1){+.+.}, at: [] pipe_wait+0x16c/0x190 fs/pipe.c:123 1 lock held by syz-executor.5/5511: #0: (&pipe->mutex/1){+.+.}, at: [] pipe_lock_nested fs/pipe.c:67 [inline] #0: (&pipe->mutex/1){+.+.}, at: [] pipe_lock fs/pipe.c:75 [inline] #0: (&pipe->mutex/1){+.+.}, at: [] pipe_wait+0x16c/0x190 fs/pipe.c:123 1 lock held by syz-executor.2/5783: #0: (&pipe->mutex/1){+.+.}, at: [] __pipe_lock fs/pipe.c:88 [inline] #0: (&pipe->mutex/1){+.+.}, at: [] pipe_write+0xa6/0xd10 fs/pipe.c:385 1 lock held by syz-executor.2/7283: #0: (&pipe->mutex/1){+.+.}, at: [] __pipe_lock fs/pipe.c:88 [inline] #0: (&pipe->mutex/1){+.+.}, at: [] pipe_write+0xa6/0xd10 fs/pipe.c:385 1 lock held by syz-executor.2/7301: #0: (&pipe->mutex/1){+.+.}, at: [] __pipe_lock fs/pipe.c:88 [inline] #0: (&pipe->mutex/1){+.+.}, at: [] pipe_write+0xa6/0xd10 fs/pipe.c:385 ============================================= NMI backtrace for cpu 1 CPU: 1 PID: 1044 Comm: khungtaskd Not tainted 4.14.171-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:17 [inline] dump_stack+0xf7/0x13b lib/dump_stack.c:58 nmi_cpu_backtrace.cold.4+0x3e/0x76 lib/nmi_backtrace.c:101 nmi_trigger_cpumask_backtrace+0xe5/0x119 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:140 [inline] check_hung_uninterruptible_tasks kernel/hung_task.c:195 [inline] watchdog+0x522/0xb40 kernel/hung_task.c:274 kthread+0x338/0x400 kernel/kthread.c:232 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404 Sending NMI from CPU 1 to CPUs 0: NMI backtrace for cpu 0 CPU: 0 PID: 5 Comm: kworker/u4:0 Not tainted 4.14.171-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Workqueue: bat_events batadv_nc_worker task: ffff8880a9cd2140 task.stack: ffff8880a9cd8000 RIP: 0010:debug_lockdep_rcu_enabled.part.3+0x0/0x60 kernel/rcu/update.c:300 RSP: 0018:ffff8880a9cdfcf8 EFLAGS: 00000202 RAX: 0000000000000001 RBX: ffff888089d99570 RCX: ffff8880a9cd29c0 RDX: 0000000000000004 RSI: ffff8880a9cd2a10 RDI: ffffffff88337fa0 RBP: ffff8880a9cdfd00 R08: ffff8880a9cd2a30 R09: 0000000000000000 R10: 0000000000000050 R11: ffff8880a9cd2140 R12: ffff88809e9964c0 R13: 000000000000023e R14: ffff88807f749330 R15: dffffc0000000000 FS: 0000000000000000(0000) GS:ffff8880aec00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f64fe9fb140 CR3: 00000000a7f1f000 CR4: 00000000001406f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: rcu_read_lock include/linux/rcupdate.h:630 [inline] batadv_nc_purge_orig_hash net/batman-adv/network-coding.c:416 [inline] batadv_nc_worker+0xf4/0x630 net/batman-adv/network-coding.c:726 process_one_work+0x79e/0x16c0 kernel/workqueue.c:2114 worker_thread+0xcc/0xee0 kernel/workqueue.c:2248 kthread+0x338/0x400 kernel/kthread.c:232 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404 Code: 00 e9 1c fe ff ff 4c 89 ef 48 89 45 a0 e8 79 9e 38 00 48 8b 45 a0 e9 bc fd ff ff 48 8b 7d d0 e8 67 9e 38 00 e9 95 fd ff ff 66 90 <48> b8 00 00 00 00 00 fc ff df 55 48 89 e5 53 65 48 8b 1c 25 40