audit: type=1400 audit(1542023997.592:1548): avc:  denied  { ioctl } for  pid=26191 comm="syz-executor1" path="socket:[82918]" dev="sockfs" ino=82918 ioctlcmd=8903 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 ]
4.4.163+ #11 Not tainted
-------------------------------------------------------
syz-executor2/26241 is trying to acquire lock:
 (&pipe->mutex/1){+.+.+.}, at: [<ffffffff814a9d6e>] pipe_lock_nested fs/pipe.c:65 [inline]
 (&pipe->mutex/1){+.+.+.}, at: [<ffffffff814a9d6e>] pipe_lock+0x5e/0x70 fs/pipe.c:73

but task is already holding lock:
 (sb_writers#4){.+.+.+}, at: [<ffffffff815315ba>] file_start_write include/linux/fs.h:2541 [inline]
 (sb_writers#4){.+.+.+}, at: [<ffffffff815315ba>] do_splice fs/splice.c:1403 [inline]
 (sb_writers#4){.+.+.+}, at: [<ffffffff815315ba>] SYSC_splice fs/splice.c:1707 [inline]
 (sb_writers#4){.+.+.+}, at: [<ffffffff815315ba>] SyS_splice+0xfaa/0x1430 fs/splice.c:1690

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

       [<ffffffff8120301e>] lock_acquire+0x15e/0x450 kernel/locking/lockdep.c:3592
       [<ffffffff81498f1e>] percpu_down_read include/linux/percpu-rwsem.h:26 [inline]
       [<ffffffff81498f1e>] __sb_start_write+0x1ae/0x310 fs/super.c:1221
       [<ffffffff816bb237>] sb_start_write include/linux/fs.h:1515 [inline]
       [<ffffffff816bb237>] ext4_run_li_request fs/ext4/super.c:2674 [inline]
       [<ffffffff816bb237>] ext4_lazyinit_thread+0x1a7/0x750 fs/ext4/super.c:2773
       [<ffffffff811340d8>] kthread+0x268/0x300 kernel/kthread.c:211
       [<ffffffff827127c5>] ret_from_fork+0x55/0x80 arch/x86/entry/entry_64.S:510

       [<ffffffff8120301e>] lock_acquire+0x15e/0x450 kernel/locking/lockdep.c:3592
       [<ffffffff82706e5b>] __mutex_lock_common kernel/locking/mutex.c:521 [inline]
       [<ffffffff82706e5b>] mutex_lock_nested+0xbb/0x8d0 kernel/locking/mutex.c:621
       [<ffffffff816c5334>] ext4_register_li_request+0x304/0x7a0 fs/ext4/super.c:2961
       [<ffffffff816c6b38>] ext4_remount+0x1368/0x1bb0 fs/ext4/super.c:4911
       [<ffffffff8149c1c8>] do_remount_sb2+0x428/0x7d0 fs/super.c:771
       [<ffffffff814fc10e>] do_remount fs/namespace.c:2335 [inline]
       [<ffffffff814fc10e>] do_mount+0x101e/0x2a10 fs/namespace.c:2848
       [<ffffffff814fe651>] SYSC_mount fs/namespace.c:3051 [inline]
       [<ffffffff814fe651>] SyS_mount+0x191/0x1c0 fs/namespace.c:3029
       [<ffffffff827123e1>] entry_SYSCALL_64_fastpath+0x1e/0x9a

       [<ffffffff8120301e>] lock_acquire+0x15e/0x450 kernel/locking/lockdep.c:3592
       [<ffffffff82706e5b>] __mutex_lock_common kernel/locking/mutex.c:521 [inline]
       [<ffffffff82706e5b>] mutex_lock_nested+0xbb/0x8d0 kernel/locking/mutex.c:621
       [<ffffffff816c50b7>] ext4_register_li_request+0x87/0x7a0 fs/ext4/super.c:2934
       [<ffffffff816c6b38>] ext4_remount+0x1368/0x1bb0 fs/ext4/super.c:4911
       [<ffffffff8149c1c8>] do_remount_sb2+0x428/0x7d0 fs/super.c:771
       [<ffffffff814fc10e>] do_remount fs/namespace.c:2335 [inline]
       [<ffffffff814fc10e>] do_mount+0x101e/0x2a10 fs/namespace.c:2848
       [<ffffffff814fe651>] SYSC_mount fs/namespace.c:3051 [inline]
       [<ffffffff814fe651>] SyS_mount+0x191/0x1c0 fs/namespace.c:3029
       [<ffffffff827123e1>] entry_SYSCALL_64_fastpath+0x1e/0x9a

       [<ffffffff8120301e>] lock_acquire+0x15e/0x450 kernel/locking/lockdep.c:3592
       [<ffffffff8270d3d2>] down_read+0x42/0x60 kernel/locking/rwsem.c:22
       [<ffffffff8149b8e1>] iterate_supers+0xe1/0x260 fs/super.c:537
       [<ffffffff819aa1b4>] selinux_complete_init+0x2f/0x31 security/selinux/hooks.c:6154
       [<ffffffff8199be06>] security_load_policy+0x886/0x9b0 security/selinux/ss/services.c:2060
       [<ffffffff81971d31>] sel_write_load+0x191/0xfc0 security/selinux/selinuxfs.c:535
       [<ffffffff81490e8c>] __vfs_write+0x11c/0x3e0 fs/read_write.c:489
       [<ffffffff81492b3e>] vfs_write+0x17e/0x4e0 fs/read_write.c:538
       [<ffffffff81495179>] SYSC_write fs/read_write.c:585 [inline]
       [<ffffffff81495179>] SyS_write+0xd9/0x1c0 fs/read_write.c:577
       [<ffffffff827123e1>] entry_SYSCALL_64_fastpath+0x1e/0x9a

       [<ffffffff8120301e>] lock_acquire+0x15e/0x450 kernel/locking/lockdep.c:3592
       [<ffffffff82706e5b>] __mutex_lock_common kernel/locking/mutex.c:521 [inline]
       [<ffffffff82706e5b>] mutex_lock_nested+0xbb/0x8d0 kernel/locking/mutex.c:621
       [<ffffffff8196f817>] sel_commit_bools_write+0x87/0x250 security/selinux/selinuxfs.c:1142
       [<ffffffff81490e8c>] __vfs_write+0x11c/0x3e0 fs/read_write.c:489
       [<ffffffff8149125a>] __kernel_write+0x10a/0x350 fs/read_write.c:511
       [<ffffffff8152c2cd>] write_pipe_buf+0x15d/0x1f0 fs/splice.c:1074
       [<ffffffff8152d164>] splice_from_pipe_feed fs/splice.c:776 [inline]
       [<ffffffff8152d164>] __splice_from_pipe+0x364/0x790 fs/splice.c:901
       [<ffffffff81530229>] splice_from_pipe+0xf9/0x170 fs/splice.c:936
       [<ffffffff8153032c>] default_file_splice_write+0x3c/0x80 fs/splice.c:1086
       [<ffffffff815313f1>] do_splice_from fs/splice.c:1128 [inline]
       [<ffffffff815313f1>] do_splice fs/splice.c:1404 [inline]
       [<ffffffff815313f1>] SYSC_splice fs/splice.c:1707 [inline]
       [<ffffffff815313f1>] SyS_splice+0xde1/0x1430 fs/splice.c:1690
       [<ffffffff8100629e>] do_syscall_32_irqs_on arch/x86/entry/common.c:396 [inline]
       [<ffffffff8100629e>] do_fast_syscall_32+0x31e/0xa80 arch/x86/entry/common.c:463
       [<ffffffff82713b50>] sysenter_flags_fixed+0xd/0x1a

       [<ffffffff811ff43c>] check_prev_add kernel/locking/lockdep.c:1853 [inline]
       [<ffffffff811ff43c>] check_prevs_add kernel/locking/lockdep.c:1958 [inline]
       [<ffffffff811ff43c>] validate_chain kernel/locking/lockdep.c:2144 [inline]
       [<ffffffff811ff43c>] __lock_acquire+0x3e6c/0x5f10 kernel/locking/lockdep.c:3213
       [<ffffffff8120301e>] lock_acquire+0x15e/0x450 kernel/locking/lockdep.c:3592
       [<ffffffff82706e5b>] __mutex_lock_common kernel/locking/mutex.c:521 [inline]
       [<ffffffff82706e5b>] mutex_lock_nested+0xbb/0x8d0 kernel/locking/mutex.c:621
       [<ffffffff814a9d6e>] pipe_lock_nested fs/pipe.c:65 [inline]
       [<ffffffff814a9d6e>] pipe_lock+0x5e/0x70 fs/pipe.c:73
       [<ffffffff8152d8d0>] iter_file_splice_write+0x160/0xb90 fs/splice.c:974
       [<ffffffff815313f1>] do_splice_from fs/splice.c:1128 [inline]
       [<ffffffff815313f1>] do_splice fs/splice.c:1404 [inline]
       [<ffffffff815313f1>] SYSC_splice fs/splice.c:1707 [inline]
       [<ffffffff815313f1>] SyS_splice+0xde1/0x1430 fs/splice.c:1690
       [<ffffffff8100629e>] do_syscall_32_irqs_on arch/x86/entry/common.c:396 [inline]
       [<ffffffff8100629e>] do_fast_syscall_32+0x31e/0xa80 arch/x86/entry/common.c:463
       [<ffffffff82713b50>] 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(&pipe->mutex/1);

 *** DEADLOCK ***

1 lock held by syz-executor2/26241:
 #0:  (sb_writers#4){.+.+.+}, at: [<ffffffff815315ba>] file_start_write include/linux/fs.h:2541 [inline]
 #0:  (sb_writers#4){.+.+.+}, at: [<ffffffff815315ba>] do_splice fs/splice.c:1403 [inline]
 #0:  (sb_writers#4){.+.+.+}, at: [<ffffffff815315ba>] SYSC_splice fs/splice.c:1707 [inline]
 #0:  (sb_writers#4){.+.+.+}, at: [<ffffffff815315ba>] SyS_splice+0xfaa/0x1430 fs/splice.c:1690

stack backtrace:
CPU: 1 PID: 26241 Comm: syz-executor2 Not tainted 4.4.163+ #11
 0000000000000000 e3c9596a92010ad7 ffff8801c0f77898 ffffffff81aa556d
 ffffffff83ac08b0 ffffffff83ab4340 ffffffff83ab5270 ffff8800a7d208e8
 ffff8800a7d20000 ffff8801c0f778e0 ffffffff813a8827 0000000000000001
Call Trace:
 [<ffffffff81aa556d>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81aa556d>] dump_stack+0xc1/0x124 lib/dump_stack.c:51
 [<ffffffff813a8827>] print_circular_bug.cold.34+0x2f7/0x432 kernel/locking/lockdep.c:1226
 [<ffffffff811ff43c>] check_prev_add kernel/locking/lockdep.c:1853 [inline]
 [<ffffffff811ff43c>] check_prevs_add kernel/locking/lockdep.c:1958 [inline]
 [<ffffffff811ff43c>] validate_chain kernel/locking/lockdep.c:2144 [inline]
 [<ffffffff811ff43c>] __lock_acquire+0x3e6c/0x5f10 kernel/locking/lockdep.c:3213
 [<ffffffff8120301e>] lock_acquire+0x15e/0x450 kernel/locking/lockdep.c:3592
 [<ffffffff82706e5b>] __mutex_lock_common kernel/locking/mutex.c:521 [inline]
 [<ffffffff82706e5b>] mutex_lock_nested+0xbb/0x8d0 kernel/locking/mutex.c:621
 [<ffffffff814a9d6e>] pipe_lock_nested fs/pipe.c:65 [inline]
 [<ffffffff814a9d6e>] pipe_lock+0x5e/0x70 fs/pipe.c:73
 [<ffffffff8152d8d0>] iter_file_splice_write+0x160/0xb90 fs/splice.c:974
 [<ffffffff815313f1>] do_splice_from fs/splice.c:1128 [inline]
 [<ffffffff815313f1>] do_splice fs/splice.c:1404 [inline]
 [<ffffffff815313f1>] SYSC_splice fs/splice.c:1707 [inline]
 [<ffffffff815313f1>] SyS_splice+0xde1/0x1430 fs/splice.c:1690
 [<ffffffff8100629e>] do_syscall_32_irqs_on arch/x86/entry/common.c:396 [inline]
 [<ffffffff8100629e>] do_fast_syscall_32+0x31e/0xa80 arch/x86/entry/common.c:463
 [<ffffffff82713b50>] sysenter_flags_fixed+0xd/0x1a
nla_parse: 2 callbacks suppressed
netlink: 3 bytes leftover after parsing attributes in process `syz-executor3'.
netlink: 3 bytes leftover after parsing attributes in process `syz-executor3'.
audit: type=1400 audit(1542023999.692:1549): avc:  denied  { create } for  pid=26263 comm="syz-executor1" 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
binder: BINDER_SET_CONTEXT_MGR already set
binder: 26275:26277 ioctl 40046207 0 returned -16
binder: 26275:26277 ioctl 40084503 20000040 returned -22
binder: 26275:26277 unknown command -1759073019
binder: 26275:26277 ioctl c0306201 20007000 returned -22
audit: type=1400 audit(1542023999.782:1550): avc:  denied  { create } for  pid=26279 comm="syz-executor4" 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(1542023999.812:1551): avc:  denied  { write } for  pid=26279 comm="syz-executor4" 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(1542023999.842:1552): avc:  denied  { create } for  pid=26279 comm="syz-executor4" 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
netlink: 3 bytes leftover after parsing attributes in process `syz-executor3'.
netlink: 3 bytes leftover after parsing attributes in process `syz-executor3'.
audit: type=1400 audit(1542023999.992:1553): avc:  denied  { create } for  pid=26287 comm="syz-executor4" 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
binder: BINDER_SET_CONTEXT_MGR already set
binder: 26275:26296 ioctl 40084503 20000040 returned -22
binder: 26275:26295 ioctl 40046207 0 returned -16
binder: 26275:26295 unknown command -1759073019
binder: 26275:26295 ioctl c0306201 20007000 returned -22
audit: type=1400 audit(1542024000.632:1554): avc:  denied  { create } for  pid=26298 comm="syz-executor4" 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
netlink: 3 bytes leftover after parsing attributes in process `syz-executor3'.
netlink: 3 bytes leftover after parsing attributes in process `syz-executor3'.
audit: type=1400 audit(1542024000.802:1555): avc:  denied  { create } for  pid=26307 comm="syz-executor1" 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
netlink: 3 bytes leftover after parsing attributes in process `syz-executor3'.
netlink: 3 bytes leftover after parsing attributes in process `syz-executor3'.
binder_alloc: binder_alloc_mmap_handler: 26341 20001000-20004000 already mapped failed -16
netlink: 3 bytes leftover after parsing attributes in process `syz-executor3'.
netlink: 3 bytes leftover after parsing attributes in process `syz-executor3'.
audit_printk_skb: 54 callbacks suppressed
audit: type=1400 audit(1542024003.202:1574): avc:  denied  { create } for  pid=26402 comm="syz-executor4" 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(1542024003.242:1575): avc:  denied  { write } for  pid=26402 comm="syz-executor4" 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(1542024003.392:1576): avc:  denied  { create } for  pid=26413 comm="syz-executor4" 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(1542024003.422:1577): avc:  denied  { write } for  pid=26413 comm="syz-executor4" 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(1542024003.642:1578): avc:  denied  { create } for  pid=26428 comm="syz-executor4" 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(1542024003.672:1579): avc:  denied  { write } for  pid=26428 comm="syz-executor4" 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(1542024003.762:1580): avc:  denied  { create } for  pid=26432 comm="syz-executor4" 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(1542024004.002:1581): avc:  denied  { create } for  pid=26438 comm="syz-executor4" 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(1542024004.032:1582): avc:  denied  { write } for  pid=26438 comm="syz-executor4" 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: syz1 as /devices/virtual/input/input104
input: syz1 as /devices/virtual/input/input105
audit: type=1400 audit(1542024004.802:1583): avc:  denied  { create } for  pid=26462 comm="syz-executor4" 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
nla_parse: 4 callbacks suppressed
netlink: 3 bytes leftover after parsing attributes in process `syz-executor3'.
netlink: 3 bytes leftover after parsing attributes in process `syz-executor3'.
netlink: 3 bytes leftover after parsing attributes in process `syz-executor3'.
netlink: 3 bytes leftover after parsing attributes in process `syz-executor3'.
hid-generic 0000:0000:0000.001E: unknown main item tag 0x0
hid-generic 0000:0000:0000.001E: unknown main item tag 0x0
hid-generic 0000:0000:0000.001E: unknown main item tag 0x0
hid-generic 0000:0000:0000.001E: unknown main item tag 0x0
hid-generic 0000:0000:0000.001E: unknown main item tag 0x0
hid-generic 0000:0000:0000.001E: unknown main item tag 0x0
hid-generic 0000:0000:0000.001E: unknown main item tag 0x0
hid-generic 0000:0000:0000.001E: unknown main item tag 0x0
hid-generic 0000:0000:0000.001E: unknown main item tag 0x0
hid-generic 0000:0000:0000.001E: unknown main item tag 0x0
hid-generic 0000:0000:0000.001E: unknown main item tag 0x0
hid-generic 0000:0000:0000.001E: hidraw0: <UNKNOWN> HID v0.00 Device [syz1] on syz1
hid-generic 0000:0000:0000.001F: unknown main item tag 0x0
hid-generic 0000:0000:0000.001F: unknown main item tag 0x0
hid-generic 0000:0000:0000.001F: unknown main item tag 0x0