bisecting fixing commit since 672481c2deffb371d8a7dfdc009e44c09864a869 building syzkaller on be5c2c81971442d623dd1b265dabf4644ceeb35b testing commit 672481c2deffb371d8a7dfdc009e44c09864a869 with gcc (GCC) 8.1.0 kernel signature: 88914823eb92ec14565a9e90da97fc721848a092eb18b33c3e7f772601d65733 all runs: crashed: possible deadlock in seq_read testing current HEAD 67957f12548c785d0e0b14fd104d2297f3a71835 testing commit 67957f12548c785d0e0b14fd104d2297f3a71835 with gcc (GCC) 8.1.0 kernel signature: 85f119e0a38259caa4fb9eaf18cb8104c71fde2adeb31aabbd7b27cb341762f8 all runs: crashed: possible deadlock in seq_read revisions tested: 2, total time: 29m33.624817798s (build: 21m10.483910114s, test: 6m23.68145138s) the crash still happens on HEAD commit msg: Linux 4.19.144 crash: possible deadlock in seq_read overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir ====================================================== WARNING: possible circular locking dependency detected 4.19.144-syzkaller #0 Not tainted ------------------------------------------------------ syz-executor.4/9346 is trying to acquire lock: 0000000088e217ea (&p->lock){+.+.}, at: seq_read+0x66/0x1000 fs/seq_file.c:161 but task is already holding lock: 00000000097bae87 (sb_writers#3){.+.+}, at: file_start_write include/linux/fs.h:2780 [inline] 00000000097bae87 (sb_writers#3){.+.+}, at: do_sendfile+0x81e/0xd00 fs/read_write.c:1446 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #3 (sb_writers#3){.+.+}: percpu_down_read_preempt_disable include/linux/percpu-rwsem.h:36 [inline] percpu_down_read include/linux/percpu-rwsem.h:59 [inline] __sb_start_write+0x17d/0x2a0 fs/super.c:1387 sb_start_write include/linux/fs.h:1579 [inline] mnt_want_write+0x3c/0xa0 fs/namespace.c:360 ovl_want_write+0x71/0x90 fs/overlayfs/util.c:24 ovl_create_object+0x8d/0x290 fs/overlayfs/dir.c:600 ovl_create+0x1e/0x20 fs/overlayfs/dir.c:631 lookup_open+0x102b/0x1d30 fs/namei.c:3235 do_last fs/namei.c:3327 [inline] path_openat+0xf40/0x3c60 fs/namei.c:3537 do_filp_open+0x177/0x250 fs/namei.c:3567 do_sys_open+0x1dd/0x350 fs/open.c:1085 __do_sys_open fs/open.c:1103 [inline] __se_sys_open fs/open.c:1098 [inline] __x64_sys_open+0x79/0xb0 fs/open.c:1098 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe -> #2 (&ovl_i_mutex_dir_key[depth]){++++}: down_read+0x3b/0xb0 kernel/locking/rwsem.c:24 inode_lock_shared include/linux/fs.h:758 [inline] do_last fs/namei.c:3326 [inline] path_openat+0x1667/0x3c60 fs/namei.c:3537 do_filp_open+0x177/0x250 fs/namei.c:3567 do_open_execat+0xe1/0x4b0 fs/exec.c:853 __do_execve_file.isra.31+0x116e/0x1d70 fs/exec.c:1757 do_execveat_common fs/exec.c:1866 [inline] do_execve fs/exec.c:1883 [inline] __do_sys_execve fs/exec.c:1964 [inline] __se_sys_execve fs/exec.c:1959 [inline] __x64_sys_execve+0x8a/0xb0 fs/exec.c:1959 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe -> #1 (&sig->cred_guard_mutex){+.+.}: __mutex_lock_common kernel/locking/mutex.c:925 [inline] __mutex_lock+0xf5/0x1210 kernel/locking/mutex.c:1072 mutex_lock_killable_nested+0x16/0x20 kernel/locking/mutex.c:1102 do_io_accounting+0x1ee/0xa60 fs/proc/base.c:2738 proc_tgid_io_accounting+0x14/0x20 fs/proc/base.c:2787 proc_single_show+0xf3/0x170 fs/proc/base.c:755 seq_read+0x3e2/0x1000 fs/seq_file.c:229 do_loop_readv_writev fs/read_write.c:701 [inline] do_iter_read+0x362/0x560 fs/read_write.c:925 vfs_readv+0xc9/0x130 fs/read_write.c:987 kernel_readv fs/splice.c:362 [inline] default_file_splice_read+0x411/0x900 fs/splice.c:417 do_splice_to+0xe3/0x120 fs/splice.c:881 splice_direct_to_actor+0x296/0x870 fs/splice.c:959 do_splice_direct+0x14c/0x270 fs/splice.c:1068 do_sendfile+0x481/0xd00 fs/read_write.c:1447 __do_sys_sendfile64 fs/read_write.c:1508 [inline] __se_sys_sendfile64 fs/read_write.c:1494 [inline] __x64_sys_sendfile64+0x198/0x1e0 fs/read_write.c:1494 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe -> #0 (&p->lock){+.+.}: lock_acquire+0x173/0x3d0 kernel/locking/lockdep.c:3907 __mutex_lock_common kernel/locking/mutex.c:925 [inline] __mutex_lock+0xf5/0x1210 kernel/locking/mutex.c:1072 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:1087 seq_read+0x66/0x1000 fs/seq_file.c:161 do_loop_readv_writev fs/read_write.c:701 [inline] do_iter_read+0x362/0x560 fs/read_write.c:925 vfs_readv+0xc9/0x130 fs/read_write.c:987 kernel_readv fs/splice.c:362 [inline] default_file_splice_read+0x411/0x900 fs/splice.c:417 do_splice_to+0xe3/0x120 fs/splice.c:881 splice_direct_to_actor+0x296/0x870 fs/splice.c:959 do_splice_direct+0x14c/0x270 fs/splice.c:1068 do_sendfile+0x481/0xd00 fs/read_write.c:1447 __do_sys_sendfile64 fs/read_write.c:1508 [inline] __se_sys_sendfile64 fs/read_write.c:1494 [inline] __x64_sys_sendfile64+0x198/0x1e0 fs/read_write.c:1494 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe other info that might help us debug this: Chain exists of: &p->lock --> &ovl_i_mutex_dir_key[depth] --> sb_writers#3 Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(sb_writers#3); lock(&ovl_i_mutex_dir_key[depth]); lock(sb_writers#3); lock(&p->lock); *** DEADLOCK *** 1 lock held by syz-executor.4/9346: #0: 00000000097bae87 (sb_writers#3){.+.+}, at: file_start_write include/linux/fs.h:2780 [inline] #0: 00000000097bae87 (sb_writers#3){.+.+}, at: do_sendfile+0x81e/0xd00 fs/read_write.c:1446 stack backtrace: CPU: 0 PID: 9346 Comm: syz-executor.4 Not tainted 4.19.144-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 print_circular_bug.isra.34.cold.55+0x1bd/0x27d kernel/locking/lockdep.c:1221 check_prev_add kernel/locking/lockdep.c:1865 [inline] check_prevs_add kernel/locking/lockdep.c:1978 [inline] validate_chain kernel/locking/lockdep.c:2419 [inline] __lock_acquire+0x30df/0x4980 kernel/locking/lockdep.c:3415 lock_acquire+0x173/0x3d0 kernel/locking/lockdep.c:3907 __mutex_lock_common kernel/locking/mutex.c:925 [inline] __mutex_lock+0xf5/0x1210 kernel/locking/mutex.c:1072 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:1087 seq_read+0x66/0x1000 fs/seq_file.c:161 do_loop_readv_writev fs/read_write.c:701 [inline] do_iter_read+0x362/0x560 fs/read_write.c:925 vfs_readv+0xc9/0x130 fs/read_write.c:987 kernel_readv fs/splice.c:362 [inline] default_file_splice_read+0x411/0x900 fs/splice.c:417 do_splice_to+0xe3/0x120 fs/splice.c:881 splice_direct_to_actor+0x296/0x870 fs/splice.c:959 do_splice_direct+0x14c/0x270 fs/splice.c:1068 do_sendfile+0x481/0xd00 fs/read_write.c:1447 __do_sys_sendfile64 fs/read_write.c:1508 [inline] __se_sys_sendfile64 fs/read_write.c:1494 [inline] __x64_sys_sendfile64+0x198/0x1e0 fs/read_write.c:1494 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x45a999 Code: 2d b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 fb b5 fb ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:00007f139f45ec78 EFLAGS: 00000246 ORIG_RAX: 0000000000000028 RAX: ffffffffffffffda RBX: 0000000000000004 RCX: 000000000045a999 RDX: 0000000000000000 RSI: 0000000000000005 RDI: 0000000000000006 RBP: 000000000075bfc8 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000209 R11: 0000000000000246 R12: 00007f139f45f6d4 R13: 00000000004c92de R14: 00000000004e1008 R15: 00000000ffffffff overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: './bus' not a directory overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir overlayfs: filesystem on './file0' not supported as upperdir