====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Not tainted ------------------------------------------------------ syz.3.936/9160 is trying to acquire lock: ffff88803a4860a0 (&p->lock){+.+.}-{4:4}, at: seq_read_iter+0xe1/0x12d0 fs/seq_file.c:182 but task is already holding lock: ffff888026ab8868 (&pipe->mutex){+.+.}-{4:4}, at: pipe_lock fs/pipe.c:91 [inline] ffff888026ab8868 (&pipe->mutex){+.+.}-{4:4}, at: pipe_lock+0x64/0x80 fs/pipe.c:88 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #3 (&pipe->mutex){+.+.}-{4:4}: __mutex_lock_common kernel/locking/mutex.c:598 [inline] __mutex_lock+0x193/0x1060 kernel/locking/mutex.c:760 anon_pipe_write+0x15d/0x1bd0 fs/pipe.c:458 __kernel_write_iter+0x720/0xb10 fs/read_write.c:619 __kernel_write+0xf5/0x140 fs/read_write.c:639 autofs_write fs/autofs/waitq.c:57 [inline] autofs_notify_daemon+0x4db/0xd60 fs/autofs/waitq.c:164 autofs_wait+0x10ca/0x1a70 fs/autofs/waitq.c:426 autofs_mount_wait+0x132/0x380 fs/autofs/root.c:255 autofs_d_automount+0x390/0x7f0 fs/autofs/root.c:401 follow_automount fs/namei.c:1459 [inline] __traverse_mounts+0x1b9/0x830 fs/namei.c:1512 traverse_mounts fs/namei.c:1541 [inline] handle_mounts fs/namei.c:1644 [inline] step_into+0x5aa/0x21a0 fs/namei.c:1989 open_last_lookups fs/namei.c:3922 [inline] path_openat+0x6db/0x2cb0 fs/namei.c:4131 do_filp_open+0x20b/0x470 fs/namei.c:4161 do_sys_openat2+0x11b/0x1d0 fs/open.c:1437 do_sys_open fs/open.c:1452 [inline] __do_sys_openat fs/open.c:1468 [inline] __se_sys_openat fs/open.c:1463 [inline] __x64_sys_openat+0x174/0x210 fs/open.c:1463 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcd/0xfa0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #2 (&sbi->pipe_mutex){+.+.}-{4:4}: __mutex_lock_common kernel/locking/mutex.c:598 [inline] __mutex_lock+0x193/0x1060 kernel/locking/mutex.c:760 autofs_write fs/autofs/waitq.c:55 [inline] autofs_notify_daemon+0x4a6/0xd60 fs/autofs/waitq.c:164 autofs_wait+0x10ca/0x1a70 fs/autofs/waitq.c:426 autofs_mount_wait+0x132/0x380 fs/autofs/root.c:255 autofs_d_automount+0x390/0x7f0 fs/autofs/root.c:401 follow_automount fs/namei.c:1459 [inline] __traverse_mounts+0x1b9/0x830 fs/namei.c:1512 traverse_mounts fs/namei.c:1541 [inline] handle_mounts fs/namei.c:1644 [inline] step_into+0x5aa/0x21a0 fs/namei.c:1989 walk_component+0xfc/0x5b0 fs/namei.c:2157 lookup_last fs/namei.c:2652 [inline] path_lookupat+0x142/0x6d0 fs/namei.c:2676 filename_lookup+0x224/0x5f0 fs/namei.c:2705 kern_path+0x35/0x50 fs/namei.c:2863 lookup_bdev+0xd8/0x280 block/bdev.c:1205 resume_store+0x1d6/0x460 kernel/power/hibernate.c:1305 kobj_attr_store+0x58/0x80 lib/kobject.c:840 sysfs_kf_write+0xf2/0x150 fs/sysfs/file.c:142 kernfs_fop_write_iter+0x3af/0x570 fs/kernfs/file.c:352 new_sync_write fs/read_write.c:593 [inline] vfs_write+0x7d3/0x11d0 fs/read_write.c:686 ksys_write+0x12a/0x250 fs/read_write.c:738 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcd/0xfa0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #1 (&of->mutex){+.+.}-{4:4}: __mutex_lock_common kernel/locking/mutex.c:598 [inline] __mutex_lock+0x193/0x1060 kernel/locking/mutex.c:760 kernfs_seq_start+0x4f/0x2a0 fs/kernfs/file.c:172 seq_read_iter+0x2c1/0x12d0 fs/seq_file.c:225 kernfs_fop_read_iter+0x46c/0x610 fs/kernfs/file.c:297 copy_splice_read+0x618/0xc20 fs/splice.c:363 do_splice_read fs/splice.c:982 [inline] do_splice_read+0x285/0x370 fs/splice.c:956 splice_direct_to_actor+0x2a1/0xa30 fs/splice.c:1086 do_splice_direct_actor fs/splice.c:1204 [inline] do_splice_direct+0x174/0x240 fs/splice.c:1230 do_sendfile+0xb06/0xe50 fs/read_write.c:1370 __do_sys_sendfile64 fs/read_write.c:1431 [inline] __se_sys_sendfile64 fs/read_write.c:1417 [inline] __x64_sys_sendfile64+0x1d8/0x220 fs/read_write.c:1417 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcd/0xfa0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #0 (&p->lock){+.+.}-{4:4}: check_prev_add kernel/locking/lockdep.c:3165 [inline] check_prevs_add kernel/locking/lockdep.c:3284 [inline] validate_chain kernel/locking/lockdep.c:3908 [inline] __lock_acquire+0x126f/0x1c90 kernel/locking/lockdep.c:5237 lock_acquire kernel/locking/lockdep.c:5868 [inline] lock_acquire+0x179/0x350 kernel/locking/lockdep.c:5825 __mutex_lock_common kernel/locking/mutex.c:598 [inline] __mutex_lock+0x193/0x1060 kernel/locking/mutex.c:760 seq_read_iter+0xe1/0x12d0 fs/seq_file.c:182 proc_reg_read_iter+0x220/0x310 fs/proc/inode.c:299 copy_splice_read+0x618/0xc20 fs/splice.c:363 do_splice_read fs/splice.c:982 [inline] do_splice_read+0x285/0x370 fs/splice.c:956 splice_file_to_pipe+0x109/0x120 fs/splice.c:1292 do_sendfile+0x400/0xe50 fs/read_write.c:1376 __do_sys_sendfile64 fs/read_write.c:1431 [inline] __se_sys_sendfile64 fs/read_write.c:1417 [inline] __x64_sys_sendfile64+0x1d8/0x220 fs/read_write.c:1417 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcd/0xfa0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f other info that might help us debug this: Chain exists of: &p->lock --> &sbi->pipe_mutex --> &pipe->mutex Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&pipe->mutex); lock(&sbi->pipe_mutex); lock(&pipe->mutex); lock(&p->lock); *** DEADLOCK *** 1 lock held by syz.3.936/9160: #0: ffff888026ab8868 (&pipe->mutex){+.+.}-{4:4}, at: pipe_lock fs/pipe.c:91 [inline] #0: ffff888026ab8868 (&pipe->mutex){+.+.}-{4:4}, at: pipe_lock+0x64/0x80 fs/pipe.c:88 stack backtrace: CPU: 2 UID: 0 PID: 9160 Comm: syz.3.936 Not tainted syzkaller #0 PREEMPT(full) Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014 Call Trace: __dump_stack lib/dump_stack.c:94 [inline] dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120 print_circular_bug+0x275/0x350 kernel/locking/lockdep.c:2043 check_noncircular+0x14c/0x170 kernel/locking/lockdep.c:2175 check_prev_add kernel/locking/lockdep.c:3165 [inline] check_prevs_add kernel/locking/lockdep.c:3284 [inline] validate_chain kernel/locking/lockdep.c:3908 [inline] __lock_acquire+0x126f/0x1c90 kernel/locking/lockdep.c:5237 lock_acquire kernel/locking/lockdep.c:5868 [inline] lock_acquire+0x179/0x350 kernel/locking/lockdep.c:5825 __mutex_lock_common kernel/locking/mutex.c:598 [inline] __mutex_lock+0x193/0x1060 kernel/locking/mutex.c:760 seq_read_iter+0xe1/0x12d0 fs/seq_file.c:182 proc_reg_read_iter+0x220/0x310 fs/proc/inode.c:299 copy_splice_read+0x618/0xc20 fs/splice.c:363 do_splice_read fs/splice.c:982 [inline] do_splice_read+0x285/0x370 fs/splice.c:956 splice_file_to_pipe+0x109/0x120 fs/splice.c:1292 do_sendfile+0x400/0xe50 fs/read_write.c:1376 __do_sys_sendfile64 fs/read_write.c:1431 [inline] __se_sys_sendfile64 fs/read_write.c:1417 [inline] __x64_sys_sendfile64+0x1d8/0x220 fs/read_write.c:1417 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcd/0xfa0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f328a38efc9 Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 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 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007f328b200038 EFLAGS: 00000246 ORIG_RAX: 0000000000000028 RAX: ffffffffffffffda RBX: 00007f328a5e5fa0 RCX: 00007f328a38efc9 RDX: 0000000000000000 RSI: 0000000000000009 RDI: 0000000000000008 RBP: 00007f328a411f91 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000008 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f328a5e6038 R14: 00007f328a5e5fa0 R15: 00007ffcb4011c98