====================================================== WARNING: possible circular locking dependency detected 4.14.183-syzkaller #0 Not tainted ------------------------------------------------------ syz-executor.3/6954 is trying to acquire lock: (&sig->cred_guard_mutex){+.+.}, at: [] lock_trace+0x3f/0xc0 fs/proc/base.c:407 but task is already holding lock: (&p->lock){+.+.}, at: [] seq_read+0xba/0x1130 fs/seq_file.c:165 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:756 [inline] __mutex_lock+0xe8/0x1430 kernel/locking/mutex.c:893 seq_read+0xba/0x1130 fs/seq_file.c:165 proc_reg_read+0xf2/0x160 fs/proc/inode.c:217 do_loop_readv_writev fs/read_write.c:695 [inline] do_loop_readv_writev fs/read_write.c:682 [inline] do_iter_read+0x3e3/0x5a0 fs/read_write.c:919 vfs_readv+0xd3/0x130 fs/read_write.c:981 kernel_readv fs/splice.c:361 [inline] default_file_splice_read+0x41d/0x870 fs/splice.c:416 do_splice_to+0xfb/0x150 fs/splice.c:880 splice_direct_to_actor+0x20a/0x730 fs/splice.c:952 do_splice_direct+0x164/0x210 fs/splice.c:1061 do_sendfile+0x469/0xaf0 fs/read_write.c:1441 SYSC_sendfile64 fs/read_write.c:1502 [inline] SyS_sendfile64+0xff/0x110 fs/read_write.c:1488 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x46/0xbb -> #2 (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+0x1a1/0x2e0 fs/super.c:1363 sb_start_write include/linux/fs.h:1549 [inline] mnt_want_write+0x3a/0xb0 fs/namespace.c:386 ovl_setattr+0x52/0x500 fs/overlayfs/inode.c:38 notify_change+0x56b/0xd10 fs/attr.c:313 utimes_common.isra.0+0x28a/0x510 fs/utimes.c:91 do_utimes+0x16f/0x270 fs/utimes.c:156 SYSC_utime fs/utimes.c:35 [inline] SyS_utime+0xe8/0x130 fs/utimes.c:24 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x46/0xbb -> #1 (&ovl_i_mutex_dir_key[depth]){++++}: down_read+0x37/0xa0 kernel/locking/rwsem.c:24 inode_lock_shared include/linux/fs.h:729 [inline] do_last fs/namei.c:3333 [inline] path_openat+0x148c/0x2aa0 fs/namei.c:3569 do_filp_open+0x18e/0x250 fs/namei.c:3603 do_open_execat+0xda/0x440 fs/exec.c:849 do_execveat_common.isra.0+0x680/0x1c50 fs/exec.c:1742 do_execve fs/exec.c:1847 [inline] SYSC_execve fs/exec.c:1928 [inline] SyS_execve+0x34/0x40 fs/exec.c:1923 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x46/0xbb -> #0 (&sig->cred_guard_mutex){+.+.}: lock_acquire+0x170/0x3f0 kernel/locking/lockdep.c:3998 __mutex_lock_common kernel/locking/mutex.c:756 [inline] __mutex_lock+0xe8/0x1430 kernel/locking/mutex.c:893 lock_trace+0x3f/0xc0 fs/proc/base.c:407 proc_pid_syscall+0x81/0x1f0 fs/proc/base.c:639 proc_single_show+0xe7/0x150 fs/proc/base.c:761 seq_read+0x4d2/0x1130 fs/seq_file.c:237 __vfs_read+0xe4/0x610 fs/read_write.c:411 vfs_read+0x131/0x330 fs/read_write.c:447 SYSC_read fs/read_write.c:574 [inline] SyS_read+0xf2/0x210 fs/read_write.c:567 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x46/0xbb other info that might help us debug this: Chain exists of: &sig->cred_guard_mutex --> sb_writers#3 --> &p->lock Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&p->lock); lock(sb_writers#3); lock(&p->lock); lock(&sig->cred_guard_mutex); *** DEADLOCK *** 2 locks held by syz-executor.3/6954: #0: (&f->f_pos_lock){+.+.}, at: [] __fdget_pos+0xa6/0xc0 fs/file.c:769 #1: (&p->lock){+.+.}, at: [] seq_read+0xba/0x1130 fs/seq_file.c:165 stack backtrace: CPU: 1 PID: 6954 Comm: syz-executor.3 Not tainted 4.14.183-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:17 [inline] dump_stack+0x1b2/0x283 lib/dump_stack.c:58 print_circular_bug.isra.0.cold+0x2dc/0x425 kernel/locking/lockdep.c:1258 check_prev_add kernel/locking/lockdep.c:1905 [inline] check_prevs_add kernel/locking/lockdep.c:2022 [inline] validate_chain kernel/locking/lockdep.c:2464 [inline] __lock_acquire+0x3057/0x42a0 kernel/locking/lockdep.c:3491 lock_acquire+0x170/0x3f0 kernel/locking/lockdep.c:3998 __mutex_lock_common kernel/locking/mutex.c:756 [inline] __mutex_lock+0xe8/0x1430 kernel/locking/mutex.c:893 lock_trace+0x3f/0xc0 fs/proc/base.c:407 proc_pid_syscall+0x81/0x1f0 fs/proc/base.c:639 proc_single_show+0xe7/0x150 fs/proc/base.c:761 seq_read+0x4d2/0x1130 fs/seq_file.c:237 __vfs_read+0xe4/0x610 fs/read_write.c:411 vfs_read+0x131/0x330 fs/read_write.c:447 SYSC_read fs/read_write.c:574 [inline] SyS_read+0xf2/0x210 fs/read_write.c:567 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x46/0xbb RIP: 0033:0x45ca69 RSP: 002b:00007fd115cfdc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000000 RAX: ffffffffffffffda RBX: 00000000004fad40 RCX: 000000000045ca69 RDX: 0000000000000092 RSI: 0000000020000240 RDI: 000000000000000d RBP: 000000000078bf00 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff R13: 000000000000087b R14: 00000000004c9ff4 R15: 00007fd115cfe6d4 XFS (nullb0): Invalid superblock magic number FAT-fs (loop5): bogus number of reserved sectors FAT-fs (loop5): Can't find a valid FAT filesystem XFS (nullb0): Invalid superblock magic number XFS (nullb0): Invalid superblock magic number XFS (nullb0): Invalid superblock magic number XFS (nullb0): Invalid superblock magic number XFS (nullb0): Invalid superblock magic number FAT-fs (loop5): bogus number of reserved sectors FAT-fs (loop5): Can't find a valid FAT filesystem FAT-fs (loop5): bogus number of reserved sectors FAT-fs (loop5): Can't find a valid FAT filesystem XFS (nullb0): Invalid superblock magic number FAT-fs (loop5): bogus number of reserved sectors FAT-fs (loop5): Can't find a valid FAT filesystem XFS (nullb0): Invalid superblock magic number FAT-fs (loop5): bogus number of reserved sectors FAT-fs (loop5): Can't find a valid FAT filesystem XFS (nullb0): Invalid superblock magic number XFS (nullb0): Invalid superblock magic number XFS (nullb0): Invalid superblock magic number FAT-fs (loop5): bogus number of reserved sectors FAT-fs (loop5): Can't find a valid FAT filesystem XFS (nullb0): Invalid superblock magic number FAT-fs (loop5): bogus number of reserved sectors FAT-fs (loop5): Can't find a valid FAT filesystem