bisecting fixing commit since 4707d8e5727387e36ea99c74d5ff0ad227700fd0 building syzkaller on e6b89e4e5adde15c0dc0a241e03dc215f2e249b3 testing commit 4707d8e5727387e36ea99c74d5ff0ad227700fd0 compiler: gcc version 8.4.1 20210217 (GCC) kernel signature: 365417d2ee33621cb144d05c030df952ca8f948b21dce47ad962081da2fae0aa run #0: crashed: INFO: task hung in pipe_write run #1: crashed: INFO: task hung in vfs_unlink run #2: crashed: INFO: task hung in pipe_read run #3: crashed: INFO: task hung in vfs_unlink 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_write run #9: crashed: INFO: task hung in vfs_unlink run #10: OK run #11: OK run #12: OK run #13: OK run #14: OK run #15: OK run #16: OK run #17: OK run #18: OK run #19: OK testing current HEAD 2950c9c5e0df6bd34af45a5168bbee345e95eae2 testing commit 2950c9c5e0df6bd34af45a5168bbee345e95eae2 compiler: gcc version 8.4.1 20210217 (GCC) kernel signature: b243f184012ae5f25835a3b0991c7a434bf29dd2bd9943c4c1b65826f2897371 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 vfs_unlink run #6: OK run #7: OK run #8: OK run #9: OK revisions tested: 2, total time: 36m8.393067537s (build: 17m43.290647973s, test: 17m53.549945826s) the crash still happens on HEAD commit msg: Linux 4.19.207 crash: INFO: task hung in vfs_unlink IPv6: ADDRCONF(NETDEV_CHANGE): batadv_slave_1: link becomes ready IPv6: ADDRCONF(NETDEV_CHANGE): veth1_to_batadv: link becomes ready INFO: task syz-executor.3:5869 blocked for more than 140 seconds. Not tainted 4.19.207-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.3 D23016 5869 1 0x00000004 Call Trace: context_switch kernel/sched/core.c:2828 [inline] __schedule+0x80c/0x1f70 kernel/sched/core.c:3517 schedule+0x7f/0x1b0 kernel/sched/core.c:3561 __rwsem_down_write_failed_common kernel/locking/rwsem-xadd.c:589 [inline] rwsem_down_write_failed+0x3bb/0x780 kernel/locking/rwsem-xadd.c:618 call_rwsem_down_write_failed+0x17/0x30 arch/x86/lib/rwsem.S:117 __down_write arch/x86/include/asm/rwsem.h:142 [inline] down_write+0x53/0x90 kernel/locking/rwsem.c:72 inode_lock include/linux/fs.h:748 [inline] vfs_unlink+0xb3/0x430 fs/namei.c:3993 do_unlinkat+0x422/0x650 fs/namei.c:4065 __do_sys_unlink fs/namei.c:4112 [inline] __se_sys_unlink fs/namei.c:4110 [inline] __x64_sys_unlink+0x39/0x50 fs/namei.c:4110 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x463cf7 Code: Bad RIP value. RSP: 002b:00007ffc4a2cc908 EFLAGS: 00000206 ORIG_RAX: 0000000000000057 RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 0000000000463cf7 RDX: 00007ffc4a2cc940 RSI: 00007ffc4a2cc940 RDI: 00007ffc4a2cc9d0 RBP: 00007ffc4a2cc9d0 R08: 0000000000000001 R09: 00007ffc4a2cc7a0 R10: 0000000000dd67c3 R11: 0000000000000206 R12: 00000000004ad490 R13: 00007ffc4a2cda80 R14: 0000000000dd66f0 R15: 0000000000000009 Showing all locks held in the system: 1 lock held by khungtaskd/1088: #0: 00000000dd42eec1 (rcu_read_lock){....}, at: debug_show_all_locks+0x5b/0x27a kernel/locking/lockdep.c:4443 1 lock held by in:imklog/5550: 3 locks held by syz-executor.3/5869: #0: 000000002edd7e7e (sb_writers#3){.+.+}, at: sb_start_write include/linux/fs.h:1579 [inline] #0: 000000002edd7e7e (sb_writers#3){.+.+}, at: mnt_want_write+0x3c/0xa0 fs/namespace.c:360 #1: 0000000033c0467d (&type->i_mutex_dir_key#3/1){+.+.}, at: inode_lock_nested include/linux/fs.h:783 [inline] #1: 0000000033c0467d (&type->i_mutex_dir_key#3/1){+.+.}, at: do_unlinkat+0x24a/0x650 fs/namei.c:4051 #2: 00000000d7f0795a (&sb->s_type->i_mutex_key#13){+.+.}, at: inode_lock include/linux/fs.h:748 [inline] #2: 00000000d7f0795a (&sb->s_type->i_mutex_key#13){+.+.}, at: vfs_unlink+0xb3/0x430 fs/namei.c:3993 2 locks held by syz-executor.3/9478: #0: 000000002edd7e7e (sb_writers#3){.+.+}, at: file_start_write include/linux/fs.h:2779 [inline] #0: 000000002edd7e7e (sb_writers#3){.+.+}, at: vfs_write+0x378/0x4d0 fs/read_write.c:548 #1: 00000000d7f0795a (&sb->s_type->i_mutex_key#13){+.+.}, at: inode_trylock include/linux/fs.h:768 [inline] #1: 00000000d7f0795a (&sb->s_type->i_mutex_key#13){+.+.}, at: ext4_file_write_iter+0x1e2/0xe50 fs/ext4/file.c:238 ============================================= NMI backtrace for cpu 1 CPU: 1 PID: 1088 Comm: khungtaskd Not tainted 4.19.207-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+0x17c/0x226 lib/dump_stack.c:118 nmi_cpu_backtrace.cold.0+0x3c/0x78 lib/nmi_backtrace.c:101 nmi_trigger_cpumask_backtrace+0xf5/0x120 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+0x347/0x410 kernel/kthread.c:259 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 skipped: idling at native_safe_halt+0x12/0x20 arch/x86/include/asm/irqflags.h:60