audit: type=1400 audit(1574629714.224:390): avc:  denied  { create } for  pid=12579 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=netlink_generic_socket permissive=1
======================================================
[ INFO: possible circular locking dependency detected ]
4.4.174+ #17 Not tainted
-------------------------------------------------------
syz-executor.0/12585 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[  335.120869] audit: type=1400 audit(1574629714.494:391): avc:  denied  { create } for  pid=12566 comm="syz-executor.0" scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tclass=netlink_generic_socket permissive=1
audit: type=1400 audit(1574629714.494:392): avc:  denied  { write } for  pid=12566 comm="syz-executor.0" scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tclass=netlink_generic_socket permissive=1
){.+.+.+}, at: [<ffffffff8149a6b6>] file_start_write include/linux/fs.h:2543 [inline]
){.+.+.+}, 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
audit: type=1400 audit(1574629714.844:393): avc:  denied  { create } for  pid=12571 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=netlink_generic_socket permissive=1
audit: type=1400 audit(1574629714.844:394): avc:  denied  { write } for  pid=12571 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=netlink_generic_socket permissive=1
audit: type=1400 audit(1574629714.894:395): avc:  denied  { ioctl } for  pid=12571 comm="syz-executor.5" path="socket:[38737]" dev="sockfs" ino=38737 ioctlcmd=4c00 scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tclass=netlink_generic_socket permissive=1
audit: type=1400 audit(1574629714.894:396): avc:  denied  { read write } for  pid=12571 comm="syz-executor.5" path="socket:[38737]" dev="sockfs" ino=38737 scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tclass=netlink_generic_socket permissive=1
       [<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
       [<ffffffff8149c401>] C_SYSC_sendfile fs/read_write.c:1305 [inline]
       [<ffffffff8149c401>] compat_SyS_sendfile+0xd1/0x160 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.0/12585:
 #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: 1 PID: 12585 Comm: syz-executor.0 Not tainted 4.4.174+ #17
 0000000000000000 a035033d59655db3 ffff8800b4257020 ffffffff81aad1a1
 ffffffff84057a80 ffff8800b48fdf00 ffffffff83ab8a20 ffffffff83abc380
 ffffffff83ac8080 ffff8800b4257070 ffffffff813abcda ffffffff83e1ef80
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
 [<ffffffff8149c401>] C_SYSC_sendfile fs/read_write.c:1305 [inline]
 [<ffffffff8149c401>] compat_SyS_sendfile+0xd1/0x160 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
audit: type=1400 audit(1574629715.814:397): avc:  denied  { write } for  pid=12579 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=netlink_generic_socket permissive=1
input: syz0 as /devices/virtual/input/input56
uinput: write device info first
input: syz0 as /devices/virtual/input/input58
audit_printk_skb: 1659 callbacks suppressed
audit: type=1400 audit(1574629719.234:951): avc:  denied  { create } for  pid=12692 comm="syz-executor.3" scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tclass=netlink_netfilter_socket permissive=1
input: syz0 as /devices/virtual/input/input60
input: syz0 as /devices/virtual/input/input61
input: syz0 as /devices/virtual/input/input59
audit: type=1400 audit(1574629720.484:952): avc:  denied  { create } for  pid=12748 comm="syz-executor.1" scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tclass=netlink_netfilter_socket permissive=1
audit: type=1400 audit(1574629720.634:953): avc:  denied  { create } for  pid=12748 comm="syz-executor.1" scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tclass=netlink_netfilter_socket permissive=1
audit: type=1400 audit(1574629721.064:954): avc:  denied  { create } for  pid=12748 comm="syz-executor.1" scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tclass=netlink_netfilter_socket permissive=1
audit: type=1400 audit(1574629721.144:955): avc:  denied  { create } for  pid=12748 comm="syz-executor.1" scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tclass=netlink_netfilter_socket permissive=1
input: syz0 as /devices/virtual/input/input62
input: syz0 as /devices/virtual/input/input63
input: syz0 as /devices/virtual/input/input64
input: syz0 as /devices/virtual/input/input65
input: syz0 as /devices/virtual/input/input66
uinput: write device info first
audit: type=1400 audit(1574629722.994:956): avc:  denied  { create } for  pid=12839 comm="syz-executor.0" scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tclass=netlink_fib_lookup_socket permissive=1
input: syz1 as /devices/virtual/input/input68
audit: type=1400 audit(1574629723.284:957): avc:  denied  { create } for  pid=12839 comm="syz-executor.0" scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tclass=netlink_fib_lookup_socket permissive=1
uinput: write device info first
input: syz1 as /devices/virtual/input/input72
audit: type=1400 audit(1574629723.994:958): avc:  denied  { create } for  pid=12876 comm="syz-executor.0" scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tclass=netlink_generic_socket permissive=1
audit: type=1400 audit(1574629724.244:959): avc:  denied  { write } for  pid=12876 comm="syz-executor.0" scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tclass=netlink_generic_socket permissive=1
uinput: write device info first