WARNING: possible circular locking dependency detected 5.4.0-syzkaller #0 Not tainted ------------------------------------------------------ syz-executor.0/14527 is trying to acquire lock: ffff888066f759a0 (&p->lock){+.+.}, at: seq_read+0x71/0x1110 fs/seq_file.c:161 but task is already holding lock: ffff888073254428 (sb_writers#4){.+.+}, at: file_start_write include/linux/fs.h:2885 [inline] ffff888073254428 (sb_writers#4){.+.+}, at: do_sendfile+0x9b9/0xd00 fs/read_write.c:1463 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #3 (sb_writers#4){.+.+}: percpu_down_read include/linux/percpu-rwsem.h:40 [inline] __sb_start_write+0x241/0x460 fs/super.c:1672 sb_start_write include/linux/fs.h:1650 [inline] mnt_want_write+0x3f/0xc0 fs/namespace.c:354 ovl_want_write+0x76/0xa0 fs/overlayfs/util.c:21 ovl_create_object+0xb3/0x2c0 fs/overlayfs/dir.c:596 ovl_create+0x28/0x30 fs/overlayfs/dir.c:627 lookup_open+0x12d5/0x1a90 fs/namei.c:3228 do_last fs/namei.c:3318 [inline] path_openat+0x14a7/0x4710 fs/namei.c:3529 do_filp_open+0x1a1/0x280 fs/namei.c:3559 do_sys_open+0x3fe/0x5d0 fs/open.c:1097 __do_sys_open fs/open.c:1115 [inline] __se_sys_open fs/open.c:1110 [inline] __x64_sys_open+0x7e/0xc0 fs/open.c:1110 do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294 entry_SYSCALL_64_after_hwframe+0x49/0xbe -> #2 (&ovl_i_mutex_dir_key[depth]){++++}: down_read+0x95/0x430 kernel/locking/rwsem.c:1495 inode_lock_shared include/linux/fs.h:801 [inline] do_last fs/namei.c:3317 [inline] path_openat+0x1e91/0x4710 fs/namei.c:3529 do_filp_open+0x1a1/0x280 fs/namei.c:3559 do_open_execat+0x137/0x690 fs/exec.c:856 __do_execve_file.isra.0+0x1702/0x22b0 fs/exec.c:1761 do_execveat_common fs/exec.c:1867 [inline] do_execve fs/exec.c:1884 [inline] __do_sys_execve fs/exec.c:1960 [inline] __se_sys_execve fs/exec.c:1955 [inline] __x64_sys_execve+0x8f/0xc0 fs/exec.c:1955 do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294 entry_SYSCALL_64_after_hwframe+0x49/0xbe -> #1 (&sig->cred_guard_mutex){+.+.}: __mutex_lock_common kernel/locking/mutex.c:959 [inline] __mutex_lock+0x156/0x13c0 kernel/locking/mutex.c:1106 mutex_lock_killable_nested+0x16/0x20 kernel/locking/mutex.c:1136 do_io_accounting+0x1f4/0x820 fs/proc/base.c:2773 proc_tgid_io_accounting+0x23/0x30 fs/proc/base.c:2822 proc_single_show+0xfd/0x1c0 fs/proc/base.c:756 seq_read+0x4ca/0x1110 fs/seq_file.c:229 do_loop_readv_writev fs/read_write.c:714 [inline] do_loop_readv_writev fs/read_write.c:701 [inline] do_iter_read+0x4a4/0x660 fs/read_write.c:935 vfs_readv+0xf0/0x160 fs/read_write.c:997 do_preadv+0x1c4/0x280 fs/read_write.c:1089 __do_sys_preadv fs/read_write.c:1139 [inline] __se_sys_preadv fs/read_write.c:1134 [inline] __x64_sys_preadv+0x9a/0xf0 fs/read_write.c:1134 do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294 entry_SYSCALL_64_after_hwframe+0x49/0xbe -> #0 (&p->lock){+.+.}: check_prev_add kernel/locking/lockdep.c:2476 [inline] check_prevs_add kernel/locking/lockdep.c:2581 [inline] validate_chain kernel/locking/lockdep.c:2971 [inline] __lock_acquire+0x2596/0x4a00 kernel/locking/lockdep.c:3955 lock_acquire+0x190/0x410 kernel/locking/lockdep.c:4485 __mutex_lock_common kernel/locking/mutex.c:959 [inline] __mutex_lock+0x156/0x13c0 kernel/locking/mutex.c:1106 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:1121 seq_read+0x71/0x1110 fs/seq_file.c:161 kernfs_fop_read+0xed/0x560 fs/kernfs/file.c:251 do_loop_readv_writev fs/read_write.c:714 [inline] do_loop_readv_writev fs/read_write.c:701 [inline] do_iter_read+0x4a4/0x660 fs/read_write.c:935 vfs_readv+0xf0/0x160 fs/read_write.c:997 kernel_readv fs/splice.c:365 [inline] default_file_splice_read+0x4fb/0xa20 fs/splice.c:422 do_splice_to+0x127/0x180 fs/splice.c:890 splice_direct_to_actor+0x320/0xa30 fs/splice.c:969 do_splice_direct+0x1da/0x2a0 fs/splice.c:1078 do_sendfile+0x597/0xd00 fs/read_write.c:1464 __do_sys_sendfile64 fs/read_write.c:1525 [inline] __se_sys_sendfile64 fs/read_write.c:1511 [inline] __x64_sys_sendfile64+0x1dd/0x220 fs/read_write.c:1511 do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294 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#4 Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(sb_writers#4); lock(&ovl_i_mutex_dir_key[depth]); lock(sb_writers#4); lock(&p->lock); *** DEADLOCK *** 1 lock held by syz-executor.0/14527: #0: ffff888073254428 (sb_writers#4){.+.+}, at: file_start_write include/linux/fs.h:2885 [inline] #0: ffff888073254428 (sb_writers#4){.+.+}, at: do_sendfile+0x9b9/0xd00 fs/read_write.c:1463 stack backtrace: CPU: 0 PID: 14527 Comm: syz-executor.0 Not tainted 5.4.0-syzkaller #0 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.12.0-59-gc9ba5276e321-prebuilt.qemu.org 04/01/2014 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x197/0x210 lib/dump_stack.c:118 print_circular_bug.isra.0.cold+0x163/0x172 kernel/locking/lockdep.c:1685 check_noncircular+0x32e/0x3e0 kernel/locking/lockdep.c:1809 check_prev_add kernel/locking/lockdep.c:2476 [inline] check_prevs_add kernel/locking/lockdep.c:2581 [inline] validate_chain kernel/locking/lockdep.c:2971 [inline] __lock_acquire+0x2596/0x4a00 kernel/locking/lockdep.c:3955 lock_acquire+0x190/0x410 kernel/locking/lockdep.c:4485 __mutex_lock_common kernel/locking/mutex.c:959 [inline] __mutex_lock+0x156/0x13c0 kernel/locking/mutex.c:1106 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:1121 seq_read+0x71/0x1110 fs/seq_file.c:161 kernfs_fop_read+0xed/0x560 fs/kernfs/file.c:251 do_loop_readv_writev fs/read_write.c:714 [inline] do_loop_readv_writev fs/read_write.c:701 [inline] do_iter_read+0x4a4/0x660 fs/read_write.c:935 vfs_readv+0xf0/0x160 fs/read_write.c:997 kernel_readv fs/splice.c:365 [inline] default_file_splice_read+0x4fb/0xa20 fs/splice.c:422 do_splice_to+0x127/0x180 fs/splice.c:890 splice_direct_to_actor+0x320/0xa30 fs/splice.c:969 do_splice_direct+0x1da/0x2a0 fs/splice.c:1078 do_sendfile+0x597/0xd00 fs/read_write.c:1464 __do_sys_sendfile64 fs/read_write.c:1525 [inline] __se_sys_sendfile64 fs/read_write.c:1511 [inline] __x64_sys_sendfile64+0x1dd/0x220 fs/read_write.c:1511 do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x45a759 Code: bd b1 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 8b b1 fb ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:00007fc3179e0c88 EFLAGS: 00000246 ORIG_RAX: 0000000000000028 RAX: ffffffffffffffda RBX: 000000000072bf00 RCX: 000000000045a759 RDX: 0000000000000000 RSI: 0000000000000004 RDI: 0000000000000005 RBP: 0000000000000004 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000080 R11: 0000000000000246 R12: 00007fc3179e16d4 R13: 00000000004afda0 R14: 00000000006f3d70 R15: 00000000ffffffff