====================================================== WARNING: possible circular locking dependency detected 4.14.166-syzkaller #0 Not tainted ------------------------------------------------------ syz-executor.0/8691 is trying to acquire lock: (&sig->cred_guard_mutex){+.+.}, at: [] do_io_accounting+0x1d6/0x7b0 fs/proc/base.c:2726 but task is already holding lock: (&p->lock){+.+.}, at: [] seq_read+0xc1/0x1280 fs/seq_file.c:165 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #3 (&p->lock){+.+.}: lock_acquire+0x16f/0x430 kernel/locking/lockdep.c:3994 __mutex_lock_common kernel/locking/mutex.c:756 [inline] __mutex_lock+0xe8/0x1470 kernel/locking/mutex.c:893 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908 seq_read+0xc1/0x1280 fs/seq_file.c:165 do_loop_readv_writev fs/read_write.c:695 [inline] do_loop_readv_writev fs/read_write.c:682 [inline] do_iter_read+0x3e2/0x5b0 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+0x421/0x870 fs/splice.c:416 do_splice_to+0x105/0x170 fs/splice.c:880 splice_direct_to_actor+0x222/0x7b0 fs/splice.c:952 do_splice_direct+0x18d/0x230 fs/splice.c:1061 EXT4-fs (loop5): VFS: Can't find ext4 filesystem do_sendfile+0x4db/0xbd0 fs/read_write.c:1441 SYSC_sendfile64 fs/read_write.c:1502 [inline] SyS_sendfile64+0x102/0x110 fs/read_write.c:1488 do_syscall_64+0x1e8/0x640 arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x42/0xb7 -> #2 (sb_writers#4){.+.+}: lock_acquire+0x16f/0x430 kernel/locking/lockdep.c:3994 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+0x1ae/0x2f0 fs/super.c:1363 sb_start_write include/linux/fs.h:1548 [inline] mnt_want_write+0x3f/0xb0 fs/namespace.c:386 ovl_want_write+0x76/0xa0 fs/overlayfs/util.c:25 ovl_xattr_set+0x4f/0x270 fs/overlayfs/inode.c:214 ovl_posix_acl_xattr_set+0x3f9/0x830 fs/overlayfs/super.c:762 __vfs_setxattr+0xd8/0x130 fs/xattr.c:150 __vfs_setxattr_noperm+0x102/0x3c0 fs/xattr.c:181 vfs_setxattr+0xc5/0xf0 fs/xattr.c:224 setxattr+0x1de/0x350 fs/xattr.c:453 path_setxattr+0x11f/0x140 fs/xattr.c:472 SYSC_lsetxattr fs/xattr.c:494 [inline] SyS_lsetxattr+0x38/0x50 fs/xattr.c:490 do_syscall_64+0x1e8/0x640 arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x42/0xb7 -> #1 (&ovl_i_mutex_dir_key[depth]){++++}: lock_acquire+0x16f/0x430 kernel/locking/lockdep.c:3994 down_read+0x3b/0xb0 kernel/locking/rwsem.c:24 inode_lock_shared include/linux/fs.h:728 [inline] do_last fs/namei.c:3330 [inline] path_openat+0x191c/0x3f70 fs/namei.c:3566 do_filp_open+0x18e/0x250 fs/namei.c:3600 do_open_execat+0xe7/0x4a0 fs/exec.c:849 do_execveat_common.isra.0+0x6d5/0x1dd0 fs/exec.c:1740 do_execve fs/exec.c:1847 [inline] SYSC_execve fs/exec.c:1928 [inline] SyS_execve+0x39/0x50 fs/exec.c:1923 do_syscall_64+0x1e8/0x640 arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x42/0xb7 -> #0 (&sig->cred_guard_mutex){+.+.}: check_prev_add kernel/locking/lockdep.c:1901 [inline] check_prevs_add kernel/locking/lockdep.c:2018 [inline] validate_chain kernel/locking/lockdep.c:2460 [inline] __lock_acquire+0x2cb3/0x4620 kernel/locking/lockdep.c:3487 lock_acquire+0x16f/0x430 kernel/locking/lockdep.c:3994 __mutex_lock_common kernel/locking/mutex.c:756 [inline] __mutex_lock+0xe8/0x1470 kernel/locking/mutex.c:893 mutex_lock_killable_nested+0x16/0x20 kernel/locking/mutex.c:923 do_io_accounting+0x1d6/0x7b0 fs/proc/base.c:2726 proc_tgid_io_accounting+0x23/0x30 fs/proc/base.c:2775 proc_single_show+0xf0/0x160 fs/proc/base.c:761 seq_read+0x51a/0x1280 fs/seq_file.c:237 do_loop_readv_writev fs/read_write.c:695 [inline] do_loop_readv_writev fs/read_write.c:682 [inline] do_iter_read+0x3e2/0x5b0 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+0x421/0x870 fs/splice.c:416 do_splice_to+0x105/0x170 fs/splice.c:880 splice_direct_to_actor+0x222/0x7b0 fs/splice.c:952 do_splice_direct+0x18d/0x230 fs/splice.c:1061 do_sendfile+0x4db/0xbd0 fs/read_write.c:1441 SYSC_sendfile64 fs/read_write.c:1502 [inline] SyS_sendfile64+0x102/0x110 fs/read_write.c:1488 do_syscall_64+0x1e8/0x640 arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x42/0xb7 other info that might help us debug this: Chain exists of: &sig->cred_guard_mutex --> sb_writers#4 --> &p->lock Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&p->lock); lock(sb_writers#4); lock(&p->lock); lock(&sig->cred_guard_mutex); *** DEADLOCK *** 1 lock held by syz-executor.0/8691: #0: (&p->lock){+.+.}, at: [] seq_read+0xc1/0x1280 fs/seq_file.c:165 stack backtrace: CPU: 0 PID: 8691 Comm: syz-executor.0 Not tainted 4.14.166-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+0x142/0x197 lib/dump_stack.c:58 print_circular_bug.isra.0.cold+0x1cc/0x28f kernel/locking/lockdep.c:1258 check_prev_add kernel/locking/lockdep.c:1901 [inline] check_prevs_add kernel/locking/lockdep.c:2018 [inline] validate_chain kernel/locking/lockdep.c:2460 [inline] __lock_acquire+0x2cb3/0x4620 kernel/locking/lockdep.c:3487 lock_acquire+0x16f/0x430 kernel/locking/lockdep.c:3994 __mutex_lock_common kernel/locking/mutex.c:756 [inline] __mutex_lock+0xe8/0x1470 kernel/locking/mutex.c:893 mutex_lock_killable_nested+0x16/0x20 kernel/locking/mutex.c:923 do_io_accounting+0x1d6/0x7b0 fs/proc/base.c:2726 proc_tgid_io_accounting+0x23/0x30 fs/proc/base.c:2775 proc_single_show+0xf0/0x160 fs/proc/base.c:761 seq_read+0x51a/0x1280 fs/seq_file.c:237 do_loop_readv_writev fs/read_write.c:695 [inline] do_loop_readv_writev fs/read_write.c:682 [inline] do_iter_read+0x3e2/0x5b0 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+0x421/0x870 fs/splice.c:416 do_splice_to+0x105/0x170 fs/splice.c:880 splice_direct_to_actor+0x222/0x7b0 fs/splice.c:952 do_splice_direct+0x18d/0x230 fs/splice.c:1061 do_sendfile+0x4db/0xbd0 fs/read_write.c:1441 SYSC_sendfile64 fs/read_write.c:1502 [inline] SyS_sendfile64+0x102/0x110 fs/read_write.c:1488 do_syscall_64+0x1e8/0x640 arch/x86/entry/common.c:292 entry_SYSCALL_64_after_hwframe+0x42/0xb7 RIP: 0033:0x45aff9 RSP: 002b:00007fe1af1d9c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000028 RAX: ffffffffffffffda RBX: 00007fe1af1da6d4 RCX: 000000000045aff9 RDX: 0000000000000000 RSI: 0000000000000004 RDI: 0000000000000005 RBP: 000000000075bfc8 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000100001 R11: 0000000000000246 R12: 00000000ffffffff R13: 00000000000008a2 R14: 00000000004c9bce R15: 000000000075bfd4 EXT4-fs (loop5): VFS: Can't find ext4 filesystem EXT4-fs (loop5): VFS: Can't find ext4 filesystem EXT4-fs (loop5): VFS: Can't find ext4 filesystem EXT4-fs (loop5): VFS: Can't find ext4 filesystem EXT4-fs (loop5): VFS: Can't find ext4 filesystem EXT4-fs (loop5): VFS: Can't find ext4 filesystem EXT4-fs (loop5): VFS: Can't find ext4 filesystem EXT4-fs (loop5): VFS: Can't find ext4 filesystem EXT4-fs (loop5): VFS: Can't find ext4 filesystem EXT4-fs (loop5): VFS: Can't find ext4 filesystem EXT4-fs (loop5): VFS: Can't find ext4 filesystem EXT4-fs (loop5): VFS: Can't find ext4 filesystem EXT4-fs (loop5): VFS: Can't find ext4 filesystem