======================================================
[ INFO: possible circular locking dependency detected ]
4.4.169+ #1 Not tainted
-------------------------------------------------------
syz-executor4/9296 is trying to acquire lock:
 (&sig->cred_guard_mutex){+.+.+.}, at: [<ffffffff815e4632>] do_io_accounting+0x1f2/0x7f0 fs/proc/base.c:2666

but task is already holding lock:
 (&p->lock){+.+.+.}, at: [<ffffffff815075d6>] seq_read+0xd6/0x1240 fs/seq_file.c:178

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

       [<ffffffff81205d7e>] lock_acquire+0x15e/0x450 kernel/locking/lockdep.c:3592
       [<ffffffff82708c01>] __mutex_lock_common kernel/locking/mutex.c:521 [inline]
       [<ffffffff82708c01>] mutex_lock_nested+0xc1/0xb80 kernel/locking/mutex.c:621
       [<ffffffff815075d6>] seq_read+0xd6/0x1240 fs/seq_file.c:178
       [<ffffffff81496a58>] do_loop_readv_writev+0x148/0x1e0 fs/read_write.c:680
       [<ffffffff814988b3>] do_readv_writev+0x573/0x6e0 fs/read_write.c:810
       [<ffffffff81498a9a>] vfs_readv+0x7a/0xb0 fs/read_write.c:834
       [<ffffffff8153598c>] kernel_readv fs/splice.c:586 [inline]
       [<ffffffff8153598c>] default_file_splice_read+0x3ac/0x8b0 fs/splice.c:662
       [<ffffffff81531b6f>] do_splice_to+0xff/0x160 fs/splice.c:1154
       [<ffffffff81531e19>] splice_direct_to_actor+0x249/0x850 fs/splice.c:1226
       [<ffffffff815325c5>] do_splice_direct+0x1a5/0x260 fs/splice.c:1337
       [<ffffffff81499ccd>] do_sendfile+0x4ed/0xba0 fs/read_write.c:1227
       [<ffffffff8149be44>] C_SYSC_sendfile fs/read_write.c:1309 [inline]
       [<ffffffff8149be44>] compat_SyS_sendfile+0x144/0x160 fs/read_write.c:1292
       [<ffffffff8100603d>] do_syscall_32_irqs_on arch/x86/entry/common.c:330 [inline]
       [<ffffffff8100603d>] do_fast_syscall_32+0x32d/0xa90 arch/x86/entry/common.c:397
       [<ffffffff82716b50>] sysenter_flags_fixed+0xd/0x1a

       [<ffffffff81205d7e>] lock_acquire+0x15e/0x450 kernel/locking/lockdep.c:3592
       [<ffffffff8149e39f>] percpu_down_read include/linux/percpu-rwsem.h:26 [inline]
       [<ffffffff8149e39f>] __sb_start_write+0x1af/0x310 fs/super.c:1221
       [<ffffffff816c27d4>] sb_start_write include/linux/fs.h:1517 [inline]
       [<ffffffff816c27d4>] ext4_run_li_request fs/ext4/super.c:2674 [inline]
       [<ffffffff816c27d4>] ext4_lazyinit_thread fs/ext4/super.c:2773 [inline]
       [<ffffffff816c27d4>] ext4_lazyinit_thread+0x1e4/0x7b0 fs/ext4/super.c:2749
       [<ffffffff811340d3>] kthread+0x273/0x310 kernel/kthread.c:211
       [<ffffffff827157c5>] ret_from_fork+0x55/0x80 arch/x86/entry/entry_64.S:537

       [<ffffffff81205d7e>] lock_acquire+0x15e/0x450 kernel/locking/lockdep.c:3592
       [<ffffffff82708c01>] __mutex_lock_common kernel/locking/mutex.c:521 [inline]
       [<ffffffff82708c01>] mutex_lock_nested+0xc1/0xb80 kernel/locking/mutex.c:621
       [<ffffffff816cc7dd>] ext4_register_li_request+0x2fd/0x7d0 fs/ext4/super.c:2961
       [<ffffffff816ce016>] ext4_remount+0x1366/0x1b90 fs/ext4/super.c:4911
       [<ffffffff814a163b>] do_remount_sb2+0x41b/0x7a0 fs/super.c:771
       [<ffffffff8150221b>] do_remount fs/namespace.c:2347 [inline]
       [<ffffffff8150221b>] do_mount+0xfdb/0x2a40 fs/namespace.c:2860
       [<ffffffff81504670>] SYSC_mount fs/namespace.c:3063 [inline]
       [<ffffffff81504670>] SyS_mount+0x130/0x1d0 fs/namespace.c:3041
       [<ffffffff827153a1>] entry_SYSCALL_64_fastpath+0x1e/0x9a

       [<ffffffff81205d7e>] lock_acquire+0x15e/0x450 kernel/locking/lockdep.c:3592
       [<ffffffff82708c01>] __mutex_lock_common kernel/locking/mutex.c:521 [inline]
       [<ffffffff82708c01>] mutex_lock_nested+0xc1/0xb80 kernel/locking/mutex.c:621
       [<ffffffff816cc569>] ext4_register_li_request+0x89/0x7d0 fs/ext4/super.c:2934
       [<ffffffff816ce016>] ext4_remount+0x1366/0x1b90 fs/ext4/super.c:4911
       [<ffffffff814a163b>] do_remount_sb2+0x41b/0x7a0 fs/super.c:771
       [<ffffffff8150221b>] do_remount fs/namespace.c:2347 [inline]
       [<ffffffff8150221b>] do_mount+0xfdb/0x2a40 fs/namespace.c:2860
       [<ffffffff81504670>] SYSC_mount fs/namespace.c:3063 [inline]
       [<ffffffff81504670>] SyS_mount+0x130/0x1d0 fs/namespace.c:3041
       [<ffffffff827153a1>] entry_SYSCALL_64_fastpath+0x1e/0x9a

       [<ffffffff81205d7e>] lock_acquire+0x15e/0x450 kernel/locking/lockdep.c:3592
       [<ffffffff82710412>] down_read+0x42/0x60 kernel/locking/rwsem.c:22
       [<ffffffff814a0d81>] iterate_supers+0xe1/0x250 fs/super.c:537
       [<ffffffff819b0297>] selinux_complete_init+0x2f/0x31 security/selinux/hooks.c:6154
       [<ffffffff819a1ddd>] security_load_policy+0x69d/0x9c0 security/selinux/ss/services.c:2060
       [<ffffffff81978705>] sel_write_load+0x175/0xf90 security/selinux/selinuxfs.c:535
       [<ffffffff814962e6>] __vfs_write+0x116/0x3d0 fs/read_write.c:489
       [<ffffffff81497fe2>] vfs_write+0x182/0x4e0 fs/read_write.c:538
       [<ffffffff8149a61c>] SYSC_write fs/read_write.c:585 [inline]
       [<ffffffff8149a61c>] SyS_write+0xdc/0x1c0 fs/read_write.c:577
       [<ffffffff827153a1>] entry_SYSCALL_64_fastpath+0x1e/0x9a

       [<ffffffff81205d7e>] lock_acquire+0x15e/0x450 kernel/locking/lockdep.c:3592
       [<ffffffff82708c01>] __mutex_lock_common kernel/locking/mutex.c:521 [inline]
       [<ffffffff82708c01>] mutex_lock_nested+0xc1/0xb80 kernel/locking/mutex.c:621
       [<ffffffff819762e9>] sel_commit_bools_write+0x89/0x260 security/selinux/selinuxfs.c:1142
       [<ffffffff814962e6>] __vfs_write+0x116/0x3d0 fs/read_write.c:489
       [<ffffffff814966b2>] __kernel_write+0x112/0x370 fs/read_write.c:511
       [<ffffffff815327dd>] write_pipe_buf+0x15d/0x1f0 fs/splice.c:1074
       [<ffffffff815334de>] splice_from_pipe_feed fs/splice.c:776 [inline]
       [<ffffffff815334de>] __splice_from_pipe+0x37e/0x7a0 fs/splice.c:901
       [<ffffffff81536558>] splice_from_pipe+0x108/0x170 fs/splice.c:936
       [<ffffffff8153664c>] default_file_splice_write+0x3c/0x80 fs/splice.c:1086
       [<ffffffff815376a1>] do_splice_from fs/splice.c:1128 [inline]
       [<ffffffff815376a1>] do_splice fs/splice.c:1404 [inline]
       [<ffffffff815376a1>] SYSC_splice fs/splice.c:1707 [inline]
       [<ffffffff815376a1>] SyS_splice+0xd71/0x13a0 fs/splice.c:1690
       [<ffffffff8100603d>] do_syscall_32_irqs_on arch/x86/entry/common.c:330 [inline]
       [<ffffffff8100603d>] do_fast_syscall_32+0x32d/0xa90 arch/x86/entry/common.c:397
       [<ffffffff82716b50>] sysenter_flags_fixed+0xd/0x1a

       [<ffffffff81205d7e>] lock_acquire+0x15e/0x450 kernel/locking/lockdep.c:3592
       [<ffffffff82708c01>] __mutex_lock_common kernel/locking/mutex.c:521 [inline]
       [<ffffffff82708c01>] mutex_lock_nested+0xc1/0xb80 kernel/locking/mutex.c:621
       [<ffffffff814b226d>] __pipe_lock fs/pipe.c:86 [inline]
       [<ffffffff814b226d>] fifo_open+0x15d/0xa00 fs/pipe.c:896
       [<ffffffff8149103f>] do_dentry_open+0x38f/0xbd0 fs/open.c:749
       [<ffffffff8149482b>] vfs_open+0x10b/0x210 fs/open.c:862
       [<ffffffff814c574f>] do_last fs/namei.c:3269 [inline]
       [<ffffffff814c574f>] path_openat+0x136f/0x4470 fs/namei.c:3406
       [<ffffffff814cc421>] do_filp_open+0x1a1/0x270 fs/namei.c:3440
       [<ffffffff814a75fc>] do_open_execat+0x10c/0x6e0 fs/exec.c:805
       [<ffffffff814acc76>] do_execveat_common.isra.0+0x6f6/0x1e90 fs/exec.c:1577
       [<ffffffff814aee58>] compat_do_execve fs/exec.c:1710 [inline]
       [<ffffffff814aee58>] C_SYSC_execve fs/exec.c:1785 [inline]
       [<ffffffff814aee58>] compat_SyS_execve+0x48/0x60 fs/exec.c:1781
       [<ffffffff8100603d>] do_syscall_32_irqs_on arch/x86/entry/common.c:330 [inline]
       [<ffffffff8100603d>] do_fast_syscall_32+0x32d/0xa90 arch/x86/entry/common.c:397
       [<ffffffff82716b50>] sysenter_flags_fixed+0xd/0x1a

       [<ffffffff81202b96>] check_prev_add kernel/locking/lockdep.c:1853 [inline]
       [<ffffffff81202b96>] check_prevs_add kernel/locking/lockdep.c:1958 [inline]
       [<ffffffff81202b96>] validate_chain kernel/locking/lockdep.c:2144 [inline]
       [<ffffffff81202b96>] __lock_acquire+0x37d6/0x4f50 kernel/locking/lockdep.c:3213
       [<ffffffff81205d7e>] lock_acquire+0x15e/0x450 kernel/locking/lockdep.c:3592
       [<ffffffff8270a312>] __mutex_lock_common kernel/locking/mutex.c:521 [inline]
       [<ffffffff8270a312>] mutex_lock_killable_nested+0xd2/0xd00 kernel/locking/mutex.c:641
       [<ffffffff815e4632>] do_io_accounting+0x1f2/0x7f0 fs/proc/base.c:2666
       [<ffffffff815e4c53>] proc_tgid_io_accounting+0x23/0x30 fs/proc/base.c:2715
       [<ffffffff815e27d6>] proc_single_show+0xf6/0x160 fs/proc/base.c:805
       [<ffffffff815079cd>] seq_read+0x4cd/0x1240 fs/seq_file.c:240
       [<ffffffff81495f26>] __vfs_read+0x116/0x3c0 fs/read_write.c:432
       [<ffffffff81497c34>] vfs_read+0x134/0x360 fs/read_write.c:454
       [<ffffffff8149a83f>] SYSC_pread64 fs/read_write.c:607 [inline]
       [<ffffffff8149a83f>] SyS_pread64+0x13f/0x170 fs/read_write.c:594
       [<ffffffff810be6f9>] sys32_pread+0x39/0x50 arch/x86/ia32/sys_ia32.c:179
       [<ffffffff8100603d>] do_syscall_32_irqs_on arch/x86/entry/common.c:330 [inline]
       [<ffffffff8100603d>] do_fast_syscall_32+0x32d/0xa90 arch/x86/entry/common.c:397
       [<ffffffff82716b50>] sysenter_flags_fixed+0xd/0x1a

other info that might help us debug this:

Chain exists of:
 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-executor4/9296:
 #0:  (&p->lock){+.+.+.}, at: [<ffffffff815075d6>] seq_read+0xd6/0x1240 fs/seq_file.c:178

stack backtrace:
CPU: 1 PID: 9296 Comm: syz-executor4 Not tainted 4.4.169+ #1
 0000000000000000 1f5fff581ffdd1de ffff8801bde3f630 ffffffff81aab9c1
 ffffffff84055ac0 ffff8801d85b2f80 ffffffff83ab46b0 ffffffff83ab6000
 ffffffff83aba1d0 ffff8801bde3f680 ffffffff813abaf4 ffffffff83e23f80
Call Trace:
 [<ffffffff81aab9c1>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81aab9c1>] dump_stack+0xc1/0x120 lib/dump_stack.c:51
 [<ffffffff813abaf4>] print_circular_bug.cold+0x2f7/0x44e kernel/locking/lockdep.c:1226
 [<ffffffff81202b96>] check_prev_add kernel/locking/lockdep.c:1853 [inline]
 [<ffffffff81202b96>] check_prevs_add kernel/locking/lockdep.c:1958 [inline]
 [<ffffffff81202b96>] validate_chain kernel/locking/lockdep.c:2144 [inline]
 [<ffffffff81202b96>] __lock_acquire+0x37d6/0x4f50 kernel/locking/lockdep.c:3213
 [<ffffffff81205d7e>] lock_acquire+0x15e/0x450 kernel/locking/lockdep.c:3592
 [<ffffffff8270a312>] __mutex_lock_common kernel/locking/mutex.c:521 [inline]
 [<ffffffff8270a312>] mutex_lock_killable_nested+0xd2/0xd00 kernel/locking/mutex.c:641
 [<ffffffff815e4632>] do_io_accounting+0x1f2/0x7f0 fs/proc/base.c:2666
 [<ffffffff815e4c53>] proc_tgid_io_accounting+0x23/0x30 fs/proc/base.c:2715
 [<ffffffff815e27d6>] proc_single_show+0xf6/0x160 fs/proc/base.c:805
 [<ffffffff815079cd>] seq_read+0x4cd/0x1240 fs/seq_file.c:240
 [<ffffffff81495f26>] __vfs_read+0x116/0x3c0 fs/read_write.c:432
 [<ffffffff81497c34>] vfs_read+0x134/0x360 fs/read_write.c:454
 [<ffffffff8149a83f>] SYSC_pread64 fs/read_write.c:607 [inline]
 [<ffffffff8149a83f>] SyS_pread64+0x13f/0x170 fs/read_write.c:594
 [<ffffffff810be6f9>] sys32_pread+0x39/0x50 arch/x86/ia32/sys_ia32.c:179
 [<ffffffff8100603d>] do_syscall_32_irqs_on arch/x86/entry/common.c:330 [inline]
 [<ffffffff8100603d>] do_fast_syscall_32+0x32d/0xa90 arch/x86/entry/common.c:397
 [<ffffffff82716b50>] sysenter_flags_fixed+0xd/0x1a
input: syz1 as /devices/virtual/input/input30
uinput: write device info first
netlink: 64 bytes leftover after parsing attributes in process `syz-executor1'.
netlink: 64 bytes leftover after parsing attributes in process `syz-executor3'.