====================================================== WARNING: possible circular locking dependency detected 5.0.0-rc4+ #52 Not tainted ------------------------------------------------------ syz-executor3/18254 is trying to acquire lock: 00000000e8474e02 (&sig->cred_guard_mutex){+.+.}, at: lock_trace+0x4a/0xe0 fs/proc/base.c:384 but task is already holding lock: 000000004fb7471f (&p->lock){+.+.}, at: seq_read+0x71/0x1130 fs/seq_file.c:161 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #3 (&p->lock){+.+.}: __mutex_lock_common kernel/locking/mutex.c:925 [inline] __mutex_lock+0x12f/0x1670 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:700 [inline] do_loop_readv_writev fs/read_write.c:687 [inline] do_iter_read+0x4a9/0x660 fs/read_write.c:921 vfs_readv+0x175/0x1c0 fs/read_write.c:983 kernel_readv fs/splice.c:362 [inline] default_file_splice_read+0x50c/0xac0 fs/splice.c:417 do_splice_to+0x12a/0x190 fs/splice.c:880 splice_direct_to_actor+0x31b/0x9d0 fs/splice.c:957 do_splice_direct+0x2c7/0x420 fs/splice.c:1066 do_sendfile+0x61a/0xe60 fs/read_write.c:1436 __do_sys_sendfile64 fs/read_write.c:1497 [inline] __se_sys_sendfile64 fs/read_write.c:1483 [inline] __x64_sys_sendfile64+0x1f8/0x240 fs/read_write.c:1483 do_syscall_64+0x1a3/0x800 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x49/0xbe -> #2 (sb_writers#5){.+.+}: 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+0x20b/0x360 fs/super.c:1389 sb_start_write include/linux/fs.h:1602 [inline] mnt_want_write+0x3f/0xc0 fs/namespace.c:357 ovl_want_write+0x76/0xa0 fs/overlayfs/util.c:24 ovl_do_remove+0x12d/0xee0 fs/overlayfs/dir.c:840 ovl_rmdir+0x1b/0x20 fs/overlayfs/dir.c:890 vfs_rmdir fs/namei.c:3879 [inline] vfs_rmdir+0x19c/0x470 fs/namei.c:3858 do_rmdir+0x474/0x580 fs/namei.c:3940 __do_sys_rmdir fs/namei.c:3958 [inline] __se_sys_rmdir fs/namei.c:3956 [inline] __x64_sys_rmdir+0x36/0x40 fs/namei.c:3956 do_syscall_64+0x1a3/0x800 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x49/0xbe -> #1 (&ovl_i_mutex_dir_key[depth]){++++}: down_read+0x8d/0x120 kernel/locking/rwsem.c:24 inode_lock_shared include/linux/fs.h:767 [inline] lookup_slow+0x4a/0x80 fs/namei.c:1687 walk_component+0x8e5/0x26a0 fs/namei.c:1810 lookup_last fs/namei.c:2273 [inline] path_lookupat.isra.0+0x1f5/0xba0 fs/namei.c:2318 filename_lookup+0x27a/0x530 fs/namei.c:2348 kern_path+0x36/0x40 fs/namei.c:2434 create_local_trace_uprobe+0x93/0x610 kernel/trace/trace_uprobe.c:1357 perf_uprobe_init+0x1a2/0x290 kernel/trace/trace_event_perf.c:316 perf_uprobe_event_init+0x106/0x1a0 kernel/events/core.c:8503 perf_try_init_event+0x137/0x2f0 kernel/events/core.c:9770 perf_init_event kernel/events/core.c:9801 [inline] perf_event_alloc.part.0+0x20bf/0x3520 kernel/events/core.c:10074 perf_event_alloc kernel/events/core.c:10430 [inline] __do_sys_perf_event_open+0xbb5/0x2f00 kernel/events/core.c:10531 __se_sys_perf_event_open kernel/events/core.c:10420 [inline] __x64_sys_perf_event_open+0xbe/0x150 kernel/events/core.c:10420 do_syscall_64+0x1a3/0x800 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x49/0xbe -> #0 (&sig->cred_guard_mutex){+.+.}: lock_acquire+0x1db/0x570 kernel/locking/lockdep.c:3841 __mutex_lock_common kernel/locking/mutex.c:925 [inline] __mutex_lock+0x12f/0x1670 kernel/locking/mutex.c:1072 mutex_lock_killable_nested+0x16/0x20 kernel/locking/mutex.c:1102 lock_trace+0x4a/0xe0 fs/proc/base.c:384 proc_pid_stack+0x1e6/0x430 fs/proc/base.c:434 proc_single_show+0xf6/0x180 fs/proc/base.c:739 seq_read+0x4db/0x1130 fs/seq_file.c:229 do_loop_readv_writev fs/read_write.c:700 [inline] do_loop_readv_writev fs/read_write.c:687 [inline] do_iter_read+0x4a9/0x660 fs/read_write.c:921 vfs_readv+0x175/0x1c0 fs/read_write.c:983 do_preadv+0x1c4/0x280 fs/read_write.c:1067 __do_sys_preadv fs/read_write.c:1117 [inline] __se_sys_preadv fs/read_write.c:1112 [inline] __x64_sys_preadv+0x9a/0xf0 fs/read_write.c:1112 do_syscall_64+0x1a3/0x800 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x49/0xbe other info that might help us debug this: Chain exists of: &sig->cred_guard_mutex --> sb_writers#5 --> &p->lock Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&p->lock); lock(sb_writers#5); lock(&p->lock); lock(&sig->cred_guard_mutex); *** DEADLOCK *** 1 lock held by syz-executor3/18254: #0: 000000004fb7471f (&p->lock){+.+.}, at: seq_read+0x71/0x1130 fs/seq_file.c:161 stack backtrace: CPU: 1 PID: 18254 Comm: syz-executor3 Not tainted 5.0.0-rc4+ #52 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+0x1db/0x2d0 lib/dump_stack.c:113 print_circular_bug.isra.0.cold+0x1cc/0x28f kernel/locking/lockdep.c:1224 check_prev_add kernel/locking/lockdep.c:1866 [inline] check_prevs_add kernel/locking/lockdep.c:1979 [inline] validate_chain kernel/locking/lockdep.c:2350 [inline] __lock_acquire+0x3014/0x4a30 kernel/locking/lockdep.c:3338 lock_acquire+0x1db/0x570 kernel/locking/lockdep.c:3841 __mutex_lock_common kernel/locking/mutex.c:925 [inline] __mutex_lock+0x12f/0x1670 kernel/locking/mutex.c:1072 mutex_lock_killable_nested+0x16/0x20 kernel/locking/mutex.c:1102 lock_trace+0x4a/0xe0 fs/proc/base.c:384 proc_pid_stack+0x1e6/0x430 fs/proc/base.c:434 proc_single_show+0xf6/0x180 fs/proc/base.c:739 seq_read+0x4db/0x1130 fs/seq_file.c:229 do_loop_readv_writev fs/read_write.c:700 [inline] do_loop_readv_writev fs/read_write.c:687 [inline] do_iter_read+0x4a9/0x660 fs/read_write.c:921 vfs_readv+0x175/0x1c0 fs/read_write.c:983 do_preadv+0x1c4/0x280 fs/read_write.c:1067 __do_sys_preadv fs/read_write.c:1117 [inline] __se_sys_preadv fs/read_write.c:1112 [inline] __x64_sys_preadv+0x9a/0xf0 fs/read_write.c:1112 do_syscall_64+0x1a3/0x800 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x458089 Code: 6d b7 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 3b b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:00007f92758c3c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000127 RAX: ffffffffffffffda RBX: 0000000000000004 RCX: 0000000000458089 RDX: 100000000000013f RSI: 0000000020000480 RDI: 0000000000000004 RBP: 000000000073bf00 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00007f92758c46d4 R13: 00000000004c4b47 R14: 00000000004d82c0 R15: 00000000ffffffff ------------[ cut here ]------------ downgrading a read lock WARNING: CPU: 0 PID: 18252 at kernel/locking/lockdep.c:3553 __lock_downgrade kernel/locking/lockdep.c:3553 [inline] WARNING: CPU: 0 PID: 18252 at kernel/locking/lockdep.c:3553 lock_downgrade+0x4d2/0x910 kernel/locking/lockdep.c:3816