====================================================== WARNING: possible circular locking dependency detected 5.1.0-rc5-next-20190418 #28 Not tainted ------------------------------------------------------ syz-executor.3/25027 is trying to acquire lock: 000000006d875c90 (&ovl_i_mutex_dir_key[depth]){++++}, at: inode_lock_shared include/linux/fs.h:782 [inline] 000000006d875c90 (&ovl_i_mutex_dir_key[depth]){++++}, at: lookup_slow+0x4a/0x80 fs/namei.c:1685 but task is already holding lock: 0000000092588d8a (&sig->cred_guard_mutex){+.+.}, at: prepare_bprm_creds fs/exec.c:1407 [inline] 0000000092588d8a (&sig->cred_guard_mutex){+.+.}, at: __do_execve_file.isra.0+0x376/0x23f0 fs/exec.c:1750 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #3 (&sig->cred_guard_mutex){+.+.}: lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:4200 __mutex_lock_common kernel/locking/mutex.c:925 [inline] __mutex_lock+0xf7/0x1310 kernel/locking/mutex.c:1072 mutex_lock_killable_nested+0x16/0x20 kernel/locking/mutex.c:1102 do_io_accounting+0x1f4/0x830 fs/proc/base.c:2739 proc_tgid_io_accounting+0x23/0x30 fs/proc/base.c:2788 proc_single_show+0xf6/0x170 fs/proc/base.c:743 seq_read+0x4db/0x1130 fs/seq_file.c:229 do_loop_readv_writev fs/read_write.c:701 [inline] do_loop_readv_writev fs/read_write.c:688 [inline] do_iter_read+0x4a9/0x660 fs/read_write.c:922 vfs_readv+0xf0/0x160 fs/read_write.c:984 do_preadv+0x1c4/0x280 fs/read_write.c:1068 __do_sys_preadv fs/read_write.c:1118 [inline] __se_sys_preadv fs/read_write.c:1113 [inline] __x64_sys_preadv+0x9a/0xf0 fs/read_write.c:1113 do_syscall_64+0x103/0x670 arch/x86/entry/common.c:298 entry_SYSCALL_64_after_hwframe+0x49/0xbe -> #2 (&p->lock){+.+.}: lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:4200 __mutex_lock_common kernel/locking/mutex.c:925 [inline] __mutex_lock+0xf7/0x1310 kernel/locking/mutex.c:1072 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:1087 seq_read+0x71/0x1130 fs/seq_file.c:161 do_loop_readv_writev fs/read_write.c:701 [inline] do_loop_readv_writev fs/read_write.c:688 [inline] do_iter_read+0x4a9/0x660 fs/read_write.c:922 vfs_readv+0xf0/0x160 fs/read_write.c:984 kernel_readv fs/splice.c:358 [inline] default_file_splice_read+0x475/0x890 fs/splice.c:413 do_splice_to+0x12a/0x190 fs/splice.c:876 splice_direct_to_actor+0x2d2/0x970 fs/splice.c:953 do_splice_direct+0x1da/0x2a0 fs/splice.c:1062 do_sendfile+0x597/0xd00 fs/read_write.c:1443 __do_sys_sendfile64 fs/read_write.c:1504 [inline] __se_sys_sendfile64 fs/read_write.c:1490 [inline] __x64_sys_sendfile64+0x1dd/0x220 fs/read_write.c:1490 do_syscall_64+0x103/0x670 arch/x86/entry/common.c:298 entry_SYSCALL_64_after_hwframe+0x49/0xbe -> #1 (sb_writers#3){.+.+}: lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:4200 percpu_down_read include/linux/percpu-rwsem.h:36 [inline] __sb_start_write+0x20b/0x360 fs/super.c:1613 sb_start_write include/linux/fs.h:1621 [inline] mnt_want_write+0x3f/0xc0 fs/namespace.c:358 ovl_want_write+0x76/0xa0 fs/overlayfs/util.c:24 ovl_create_object+0xb3/0x2c0 fs/overlayfs/dir.c:599 ovl_create+0x28/0x30 fs/overlayfs/dir.c:630 lookup_open+0x12e0/0x1b10 fs/namei.c:3232 do_last fs/namei.c:3322 [inline] path_openat+0x14ac/0x46e0 fs/namei.c:3533 do_filp_open+0x1a1/0x280 fs/namei.c:3563 do_sys_open+0x3fe/0x5d0 fs/open.c:1069 ksys_open include/linux/syscalls.h:1373 [inline] __do_sys_creat fs/open.c:1127 [inline] __se_sys_creat fs/open.c:1125 [inline] __x64_sys_creat+0x61/0x80 fs/open.c:1125 do_syscall_64+0x103/0x670 arch/x86/entry/common.c:298 entry_SYSCALL_64_after_hwframe+0x49/0xbe -> #0 (&ovl_i_mutex_dir_key[depth]){++++}: check_prevs_add kernel/locking/lockdep.c:2322 [inline] validate_chain kernel/locking/lockdep.c:2703 [inline] __lock_acquire+0x239c/0x3fb0 kernel/locking/lockdep.c:3690 lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:4200 down_read+0x3f/0x1a0 kernel/locking/rwsem.c:24 inode_lock_shared include/linux/fs.h:782 [inline] lookup_slow+0x4a/0x80 fs/namei.c:1685 walk_component+0x74b/0x2000 fs/namei.c:1808 link_path_walk.part.0+0x980/0x1340 fs/namei.c:2139 link_path_walk fs/namei.c:2070 [inline] path_openat+0x202/0x46e0 fs/namei.c:3532 do_filp_open+0x1a1/0x280 fs/namei.c:3563 do_open_execat+0x137/0x690 fs/exec.c:856 __do_execve_file.isra.0+0x178d/0x23f0 fs/exec.c:1758 do_execveat_common fs/exec.c:1865 [inline] do_execve fs/exec.c:1882 [inline] __do_sys_execve fs/exec.c:1958 [inline] __se_sys_execve fs/exec.c:1953 [inline] __x64_sys_execve+0x8f/0xc0 fs/exec.c:1953 do_syscall_64+0x103/0x670 arch/x86/entry/common.c:298 entry_SYSCALL_64_after_hwframe+0x49/0xbe other info that might help us debug this: Chain exists of: &ovl_i_mutex_dir_key[depth] --> &p->lock --> &sig->cred_guard_mutex Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&sig->cred_guard_mutex); lock(&p->lock); lock(&sig->cred_guard_mutex); lock(&ovl_i_mutex_dir_key[depth]); *** DEADLOCK *** 1 lock held by syz-executor.3/25027: #0: 0000000092588d8a (&sig->cred_guard_mutex){+.+.}, at: prepare_bprm_creds fs/exec.c:1407 [inline] #0: 0000000092588d8a (&sig->cred_guard_mutex){+.+.}, at: __do_execve_file.isra.0+0x376/0x23f0 fs/exec.c:1750 stack backtrace: CPU: 0 PID: 25027 Comm: syz-executor.3 Not tainted 5.1.0-rc5-next-20190418 #28 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+0x172/0x1f0 lib/dump_stack.c:113 print_circular_bug.isra.0.cold+0x1cc/0x28f kernel/locking/lockdep.c:1560 check_prev_add.constprop.0+0xf11/0x23c0 kernel/locking/lockdep.c:2209 check_prevs_add kernel/locking/lockdep.c:2322 [inline] validate_chain kernel/locking/lockdep.c:2703 [inline] __lock_acquire+0x239c/0x3fb0 kernel/locking/lockdep.c:3690 lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:4200 down_read+0x3f/0x1a0 kernel/locking/rwsem.c:24 inode_lock_shared include/linux/fs.h:782 [inline] lookup_slow+0x4a/0x80 fs/namei.c:1685 walk_component+0x74b/0x2000 fs/namei.c:1808 link_path_walk.part.0+0x980/0x1340 fs/namei.c:2139 link_path_walk fs/namei.c:2070 [inline] path_openat+0x202/0x46e0 fs/namei.c:3532 do_filp_open+0x1a1/0x280 fs/namei.c:3563 do_open_execat+0x137/0x690 fs/exec.c:856 __do_execve_file.isra.0+0x178d/0x23f0 fs/exec.c:1758 do_execveat_common fs/exec.c:1865 [inline] do_execve fs/exec.c:1882 [inline] __do_sys_execve fs/exec.c:1958 [inline] __se_sys_execve fs/exec.c:1953 [inline] __x64_sys_execve+0x8f/0xc0 fs/exec.c:1953 do_syscall_64+0x103/0x670 arch/x86/entry/common.c:298 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x458c29 Code: ad b8 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 7b b8 fb ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:00007fc265fd8c78 EFLAGS: 00000246 ORIG_RAX: 000000000000003b RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000458c29 RDX: 0000000020000840 RSI: 0000000020000500 RDI: 0000000020000100 RBP: 000000000073bf00 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00007fc265fd96d4 R13: 00000000004bf216 R14: 00000000004d0458 R15: 00000000ffffffff overlayfs: './file0' not a directory