======================================================
[ INFO: possible circular locking dependency detected ]
4.4.174+ #17 Not tainted
-------------------------------------------------------
syz-executor.1/4497 is trying to acquire lock:
 (sel_mutex){+.+.+.}, at: [<ffffffff81977109>] sel_read_policy+0x59/0x110 security/selinux/selinuxfs.c:441

but task is already holding lock:
 (sb_writers#4){.+.+.+}, at: [<ffffffff8149a6b6>] file_start_write include/linux/fs.h:2543 [inline]
 (sb_writers#4){.+.+.+}, at: [<ffffffff8149a6b6>] do_sendfile+0x8a6/0xba0 fs/read_write.c:1228

which lock already depends on the new lock.

netlink: 8 bytes leftover after parsing attributes in process `syz-executor.4'.
netlink: 8 bytes leftover after parsing attributes in process `syz-executor.4'.
audit: type=1400 audit(1575182238.528:21): avc:  denied  { transfer } for  pid=4503 comm="syz-executor.5" scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tclass=binder permissive=1
binder: 4503:4504 got transaction with invalid handle, 0
binder: 4503:4504 transaction failed 29201/-22, size 88-24 line 3228
binder: BINDER_SET_CONTEXT_MGR already set
binder: 4503:4504 ioctl 40046207 0 returned -16
binder_alloc: 4503: binder_alloc_buf, no vma
binder: 4503:4505 transaction failed 29189/-3, size 88-24 line 3137
binder: BINDER_SET_CONTEXT_MGR already set
binder: 4506:4507 ioctl 40046207 0 returned -16
binder_alloc: 4503: binder_alloc_buf, no vma
binder: 4506:4507 transaction failed 29189/-3, size 88-24 line 3137

the existing dependency chain (in reverse order) is:

       [<ffffffff81205f6e>] lock_acquire+0x15e/0x450 kernel/locking/lockdep.c:3592
       [  121.571369] binder: BINDER_SET_CONTEXT_MGR already set
binder: 4508:4509 ioctl 40046207 0 returned -16
binder_alloc: 4503: binder_alloc_buf, no vma
binder: 4508:4509 transaction failed 29189/-3, size 88-24 line 3137
[<ffffffff8149ea2f>] percpu_down_read include/linux/percpu-rwsem.h:26 [inline]
[<ffffffff8149ea2f>] __sb_start_write+0x1af/0x310 fs/super.c:1239
       [<ffffffff816c3af4>] sb_start_write include/linux/fs.h:1517 [inline]
       [<ffffffff816c3af4>] ext4_run_li_request fs/ext4/super.c:2685 [inline]
       [<ffffffff816c3af4>] ext4_lazyinit_thread fs/ext4/super.c:2784 [inline]
       [<ffffffff816c3af4>] ext4_lazyinit_thread+0x1e4/0x7b0 fs/ext4/super.c:2760
       [<ffffffff811342c3>] kthread+0x273/0x310 kernel/kthread.c:211
       [<ffffffff82718fc5>] ret_from_fork+0x55/0x80 arch/x86/entry/entry_64.S:537

binder: 4510:4511 ioctl 40046207 0 returned -16
binder_alloc: 4503: binder_alloc_buf, no vma
binder: 4510:4511 transaction failed 29189/-3, size 88-24 line 3137
 (&eli->li_list_mtx){+.+...}:
       [<ffffffff81205f6e>] lock_acquire+0x15e/0x450 kernel/locking/lockdep.c:3592
       [<ffffffff8270c191>] __mutex_lock_common kernel/locking/mutex.c:521 [inline]
       [<ffffffff8270c191>] mutex_lock_nested+0xc1/0xb80 kernel/locking/mutex.c:621
       [<ffffffff816cdacd>] ext4_register_li_request+0x2fd/0x7d0 fs/ext4/super.c:2972
       [<ffffffff816cf306>] ext4_remount+0x1366/0x1b90 fs/ext4/super.c:4922
       [<ffffffff814a1ccb>] do_remount_sb2+0x41b/0x7a0 fs/super.c:781
       [<ffffffff815028ab>] do_remount fs/namespace.c:2347 [inline]
       [<ffffffff815028ab>] do_mount+0xfdb/0x2a40 fs/namespace.c:2860
       [<ffffffff81504d00>] SYSC_mount fs/namespace.c:3063 [inline]
       [<ffffffff81504d00>] SyS_mount+0x130/0x1d0 fs/namespace.c:3041
binder: undelivered TRANSACTION_ERROR: 29189
binder: undelivered TRANSACTION_ERROR: 29189
binder: undelivered TRANSACTION_ERROR: 29189
binder: undelivered TRANSACTION_ERROR: 29189
binder: undelivered TRANSACTION_ERROR: 29201
       [<ffffffff82718ba1>] entry_SYSCALL_64_fastpath+0x1e/0x9a

       [<ffffffff81205f6e>] lock_acquire+0x15e/0x450 kernel/locking/lockdep.c:3592
       [<ffffffff8270c191>] __mutex_lock_common kernel/locking/mutex.c:521 [inline]
       [<ffffffff8270c191>] mutex_lock_nested+0xc1/0xb80 kernel/locking/mutex.c:621
       [<ffffffff816cd859>] ext4_register_li_request+0x89/0x7d0 fs/ext4/super.c:2945
       [<ffffffff816cf306>] ext4_remount+0x1366/0x1b90 fs/ext4/super.c:4922
       [<ffffffff814a1ccb>] do_remount_sb2+0x41b/0x7a0 fs/super.c:781
       [<ffffffff815028ab>] do_remount fs/namespace.c:2347 [inline]
       [<ffffffff815028ab>] do_mount+0xfdb/0x2a40 fs/namespace.c:2860
       [<ffffffff81504d00>] SYSC_mount fs/namespace.c:3063 [inline]
       [<ffffffff81504d00>] SyS_mount+0x130/0x1d0 fs/namespace.c:3041
       [<ffffffff82718ba1>] entry_SYSCALL_64_fastpath+0x1e/0x9a

       [<ffffffff81205f6e>] lock_acquire+0x15e/0x450 kernel/locking/lockdep.c:3592
       [<ffffffff827139a2>] down_read+0x42/0x60 kernel/locking/rwsem.c:22
       [<ffffffff814a1411>] iterate_supers+0xe1/0x250 fs/super.c:547
       [<ffffffff819b19f7>] selinux_complete_init+0x2f/0x31 security/selinux/hooks.c:6154
       [<ffffffff819a353d>] security_load_policy+0x69d/0x9c0 security/selinux/ss/services.c:2060
       [<ffffffff81979e55>] sel_write_load+0x175/0xf90 security/selinux/selinuxfs.c:535
       [<ffffffff81496916>] __vfs_write+0x116/0x3d0 fs/read_write.c:491
       [<ffffffff81498612>] vfs_write+0x182/0x4e0 fs/read_write.c:540
       [<ffffffff8149ac4c>] SYSC_write fs/read_write.c:587 [inline]
       [<ffffffff8149ac4c>] SyS_write+0xdc/0x1c0 fs/read_write.c:579
       [<ffffffff82718ba1>] entry_SYSCALL_64_fastpath+0x1e/0x9a

       [<ffffffff81202d86>] check_prev_add kernel/locking/lockdep.c:1853 [inline]
       [<ffffffff81202d86>] check_prevs_add kernel/locking/lockdep.c:1958 [inline]
       [<ffffffff81202d86>] validate_chain kernel/locking/lockdep.c:2144 [inline]
       [<ffffffff81202d86>] __lock_acquire+0x37d6/0x4f50 kernel/locking/lockdep.c:3213
       [<ffffffff81205f6e>] lock_acquire+0x15e/0x450 kernel/locking/lockdep.c:3592
       [<ffffffff8270c191>] __mutex_lock_common kernel/locking/mutex.c:521 [inline]
       [<ffffffff8270c191>] mutex_lock_nested+0xc1/0xb80 kernel/locking/mutex.c:621
       [<ffffffff81977109>] sel_read_policy+0x59/0x110 security/selinux/selinuxfs.c:441
       [<ffffffff81497088>] do_loop_readv_writev+0x148/0x1e0 fs/read_write.c:682
       [<ffffffff81498ee3>] do_readv_writev+0x573/0x6e0 fs/read_write.c:812
       [<ffffffff814990ca>] vfs_readv+0x7a/0xb0 fs/read_write.c:836
       [<ffffffff8153601c>] kernel_readv fs/splice.c:586 [inline]
       [<ffffffff8153601c>] default_file_splice_read+0x3ac/0x8b0 fs/splice.c:662
       [<ffffffff815321ff>] do_splice_to+0xff/0x160 fs/splice.c:1154
       [<ffffffff815324a9>] splice_direct_to_actor+0x249/0x850 fs/splice.c:1226
       [<ffffffff81532c55>] do_splice_direct+0x1a5/0x260 fs/splice.c:1337
       [<ffffffff8149a2fd>] do_sendfile+0x4ed/0xba0 fs/read_write.c:1229
       [<ffffffff8149c474>] C_SYSC_sendfile fs/read_write.c:1311 [inline]
       [<ffffffff8149c474>] compat_SyS_sendfile+0x144/0x160 fs/read_write.c:1294
       [<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
       [<ffffffff8271a350>] sysenter_flags_fixed+0xd/0x1a

other info that might help us debug this:

Chain exists of:
 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(sb_writers#4);
                               lock(&eli->li_list_mtx);
                               lock(sb_writers#4);
  lock(sel_mutex);

 *** DEADLOCK ***

1 lock held by syz-executor.1/4497:
 #0:  (sb_writers#4){.+.+.+}, at: [<ffffffff8149a6b6>] file_start_write include/linux/fs.h:2543 [inline]
 #0:  (sb_writers#4){.+.+.+}, at: [<ffffffff8149a6b6>] do_sendfile+0x8a6/0xba0 fs/read_write.c:1228

stack backtrace:
CPU: 0 PID: 4497 Comm: syz-executor.1 Not tainted 4.4.174+ #17
 0000000000000000 735ba8f5f3097364 ffff8800ba727020 ffffffff81aad1a1
 ffffffff84057a80 ffff8801d74cdf00 ffffffff83ab8a20 ffffffff83abc380
 ffffffff83ac8080 ffff8800ba727070 ffffffff813abcda ffffffff83e1ee80
Call Trace:
 [<ffffffff81aad1a1>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81aad1a1>] dump_stack+0xc1/0x120 lib/dump_stack.c:51
 [<ffffffff813abcda>] print_circular_bug.cold+0x2f7/0x44e kernel/locking/lockdep.c:1226
 [<ffffffff81202d86>] check_prev_add kernel/locking/lockdep.c:1853 [inline]
 [<ffffffff81202d86>] check_prevs_add kernel/locking/lockdep.c:1958 [inline]
 [<ffffffff81202d86>] validate_chain kernel/locking/lockdep.c:2144 [inline]
 [<ffffffff81202d86>] __lock_acquire+0x37d6/0x4f50 kernel/locking/lockdep.c:3213
 [<ffffffff81205f6e>] lock_acquire+0x15e/0x450 kernel/locking/lockdep.c:3592
 [<ffffffff8270c191>] __mutex_lock_common kernel/locking/mutex.c:521 [inline]
 [<ffffffff8270c191>] mutex_lock_nested+0xc1/0xb80 kernel/locking/mutex.c:621
 [<ffffffff81977109>] sel_read_policy+0x59/0x110 security/selinux/selinuxfs.c:441
 [<ffffffff81497088>] do_loop_readv_writev+0x148/0x1e0 fs/read_write.c:682
 [<ffffffff81498ee3>] do_readv_writev+0x573/0x6e0 fs/read_write.c:812
 [<ffffffff814990ca>] vfs_readv+0x7a/0xb0 fs/read_write.c:836
 [<ffffffff8153601c>] kernel_readv fs/splice.c:586 [inline]
 [<ffffffff8153601c>] default_file_splice_read+0x3ac/0x8b0 fs/splice.c:662
 [<ffffffff815321ff>] do_splice_to+0xff/0x160 fs/splice.c:1154
 [<ffffffff815324a9>] splice_direct_to_actor+0x249/0x850 fs/splice.c:1226
 [<ffffffff81532c55>] do_splice_direct+0x1a5/0x260 fs/splice.c:1337
 [<ffffffff8149a2fd>] do_sendfile+0x4ed/0xba0 fs/read_write.c:1229
 [<ffffffff8149c474>] C_SYSC_sendfile fs/read_write.c:1311 [inline]
 [<ffffffff8149c474>] compat_SyS_sendfile+0x144/0x160 fs/read_write.c:1294
 [<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
 [<ffffffff8271a350>] sysenter_flags_fixed+0xd/0x1a
binder: 4519:4520 got transaction with invalid handle, 0
binder: 4519:4520 transaction failed 29201/-22, size 88-24 line 3228
input: syz1 as /devices/virtual/input/input24
binder: undelivered TRANSACTION_ERROR: 29201
binder: 4529:4534 got transaction with invalid handle, 0
binder: 4532:4535 got transaction with invalid handle, 0
binder: 4532:4535 transaction failed 29201/-22, size 88-24 line 3228
binder: 4529:4534 transaction failed 29201/-22, size 88-24 line 3228
binder: undelivered TRANSACTION_ERROR: 29201
binder: undelivered TRANSACTION_ERROR: 29201
binder: 4549:4551 got transaction with invalid handle, 0
binder: 4552:4555 got transaction with invalid handle, 0
binder: 4549:4551 transaction failed 29201/-22, size 88-24 line 3228
binder: 4552:4555 transaction failed 29201/-22, size 88-24 line 3228
binder: undelivered TRANSACTION_ERROR: 29201
binder: undelivered TRANSACTION_ERROR: 29201
binder: 4569:4572 got transaction with invalid handle, 0
binder: 4573:4574 got transaction with invalid handle, 0
binder: 4573:4574 transaction failed 29201/-22, size 88-24 line 3228
binder_alloc: 4570: binder_alloc_buf, no vma
binder: undelivered TRANSACTION_ERROR: 29201
binder: 4570:4576 transaction failed 29189/-3, size 88-24 line 3137
binder: 4583:4586 got transaction with invalid handle, 0
binder: 4569:4572 transaction failed 29201/-22, size 88-24 line 3228
binder: undelivered TRANSACTION_ERROR: 29189
binder: undelivered TRANSACTION_ERROR: 29201
binder: 4583:4586 transaction failed 29201/-22, size 88-24 line 3228
binder: undelivered TRANSACTION_ERROR: 29201
binder: 4596:4599 transaction failed 29189/-22, size 88-24 line 3014
binder: 4598:4602 got transaction with invalid handle, 0
binder: undelivered TRANSACTION_ERROR: 29189
binder: 4598:4602 transaction failed 29201/-22, size 88-24 line 3228
binder: undelivered TRANSACTION_ERROR: 29201
binder: 4610:4613 transaction failed 29189/-22, size 88-24 line 3014
binder: undelivered TRANSACTION_ERROR: 29189
binder: 4637:4646 transaction failed 29189/-22, size 88-24 line 3014
binder: undelivered TRANSACTION_ERROR: 29189
binder: 4754:4758 transaction failed 29189/-22, size 88-24 line 3014
binder: undelivered TRANSACTION_ERROR: 29189
binder: 4772:4778 transaction failed 29189/-22, size 88-24 line 3014
binder: undelivered TRANSACTION_ERROR: 29189
binder: 4789:4791 transaction failed 29189/-22, size 88-24 line 3014
binder: undelivered TRANSACTION_ERROR: 29189
binder: 4839:4840 ioctl c0306201 0 returned -14
binder: 4864:4866 ioctl c0306201 0 returned -14
binder: 4877:4878 ioctl c0306201 0 returned -14
binder_alloc: 4948: binder_alloc_buf, no vma
binder: 4948:4955 transaction failed 29189/-3, size 0-24 line 3137
binder: undelivered TRANSACTION_ERROR: 29189
binder_alloc: 4968: binder_alloc_buf, no vma
binder: 4968:4972 transaction failed 29189/-3, size 0-0 line 3137
binder: undelivered TRANSACTION_ERROR: 29189