======================================================
[ INFO: possible circular locking dependency detected ]
4.4.174+ #17 Not tainted
-------------------------------------------------------
syz-executor.0/4330 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.


the existing dependency chain (in reverse order) is:

       [<ffffffff81205f6e>] lock_acquire+0x15e/0x450 kernel/locking/lockdep.c:3592
       [<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

       [<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
       [<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.0/4330:
 #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: 4330 Comm: syz-executor.0 Not tainted 4.4.174+ #17
 0000000000000000 a7ca7879876ac962 ffff8801d7c4f020 ffffffff81aad1a1
 ffffffff84057a80 ffff8800b9295f00 ffffffff83ab86c0 ffffffff83abc020
 ffffffff83ac7d20 ffff8801d7c4f070 ffffffff813abcda ffffffff83e1eb80
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
input: syz1 as /devices/virtual/input/input14
input: syz1 as /devices/virtual/input/input15
netlink: 1 bytes leftover after parsing attributes in process `syz-executor.0'.
netlink: 1 bytes leftover after parsing attributes in process `syz-executor.0'.
netlink: 1 bytes leftover after parsing attributes in process `syz-executor.0'.
SELinux: unrecognized netlink message: protocol=0 nlmsg_type=0 sclass=netlink_route_socket
netlink: 1 bytes leftover after parsing attributes in process `syz-executor.0'.
netlink: 1 bytes leftover after parsing attributes in process `syz-executor.0'.
netlink: 1 bytes leftover after parsing attributes in process `syz-executor.0'.
netlink: 1 bytes leftover after parsing attributes in process `syz-executor.0'.
netlink: 1 bytes leftover after parsing attributes in process `syz-executor.0'.
netlink: 1 bytes leftover after parsing attributes in process `syz-executor.0'.
netlink: 1 bytes leftover after parsing attributes in process `syz-executor.0'.
audit: type=1400 audit(1574636492.199:23): avc:  denied  { create } for  pid=4455 comm="syz-executor.1" scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=system_u:object_r:semanage_trans_lock_t:s0 tclass=udp_socket permissive=1
audit: type=1400 audit(1574636492.339:24): avc:  denied  { create } for  pid=4455 comm="syz-executor.1" scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=system_u:object_r:semanage_trans_lock_t:s0 tclass=packet_socket permissive=1
audit: type=1400 audit(1574636492.439:25): avc:  denied  { setopt } for  pid=4455 comm="syz-executor.1" scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=system_u:object_r:semanage_trans_lock_t:s0 tclass=packet_socket permissive=1
device sit0 entered promiscuous mode
device sit0 left promiscuous mode
device sit0 entered promiscuous mode
device sit0 left promiscuous mode
device sit0 entered promiscuous mode
device sit0 left promiscuous mode
device sit0 entered promiscuous mode
device sit0 left promiscuous mode
device sit0 entered promiscuous mode
device sit0 left promiscuous mode
device sit0 entered promiscuous mode
device sit0 left promiscuous mode
device sit0 entered promiscuous mode