audit: type=1400 audit(1540797494.321:178): avc:  denied  { create } for  pid=16525 comm="syz-executor5" 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 ]
4.4.162+ #7 Not tainted
-------------------------------------------------------
syz-executor0/16549 is trying to acquire lock:
 (&sig->cred_guard_mutex){+.+.+.}, at: [<ffffffff815dce1b>] do_io_accounting+0x1fb/0x7e0 fs/proc/base.c:2661

but task is already holding lock:
 (&p->lock){+.+.+.}, at: [<ffffffff8150127d>] seq_read+0xdd/0x12b0 fs/seq_file.c:178

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

       [<ffffffff81202cde>] lock_acquire+0x15e/0x450 kernel/locking/lockdep.c:3592
       [<ffffffff826fad9b>] __mutex_lock_common kernel/locking/mutex.c:521 [inline]
       [<ffffffff826fad9b>] mutex_lock_nested+0xbb/0x8d0 kernel/locking/mutex.c:621
       [<ffffffff8150127d>] seq_read+0xdd/0x12b0 fs/seq_file.c:178
       [<ffffffff815d862d>] proc_reg_read+0xfd/0x180 fs/proc/inode.c:202
       [<ffffffff81491378>] do_loop_readv_writev+0x148/0x1e0 fs/read_write.c:680
       [<ffffffff814931b1>] do_readv_writev+0x581/0x6f0 fs/read_write.c:810
       [<ffffffff81493398>] vfs_readv+0x78/0xb0 fs/read_write.c:834
       [<ffffffff8152f53f>] kernel_readv fs/splice.c:586 [inline]
       [<ffffffff8152f53f>] default_file_splice_read+0x50f/0x8f0 fs/splice.c:662
       [<ffffffff8152b417>] do_splice_to+0xf7/0x140 fs/splice.c:1154
       [<ffffffff8152b6a2>] splice_direct_to_actor+0x242/0x830 fs/splice.c:1226
       [<ffffffff8152be33>] do_splice_direct+0x1a3/0x270 fs/splice.c:1337
       [<ffffffff814945d4>] do_sendfile+0x4e4/0xb80 fs/read_write.c:1227
       [<ffffffff81496793>] C_SYSC_sendfile fs/read_write.c:1309 [inline]
       [<ffffffff81496793>] compat_SyS_sendfile+0x143/0x160 fs/read_write.c:1292
       [<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
       [<ffffffff82707a50>] sysenter_flags_fixed+0xd/0x1a

       [<ffffffff81202cde>] lock_acquire+0x15e/0x450 kernel/locking/lockdep.c:3592
       [<ffffffff81498cae>] percpu_down_read include/linux/percpu-rwsem.h:26 [inline]
       [<ffffffff81498cae>] __sb_start_write+0x1ae/0x310 fs/super.c:1221
       [<ffffffff816bafc7>] sb_start_write include/linux/fs.h:1515 [inline]
       [<ffffffff816bafc7>] ext4_run_li_request fs/ext4/super.c:2674 [inline]
       [<ffffffff816bafc7>] ext4_lazyinit_thread+0x1a7/0x750 fs/ext4/super.c:2773
       [<ffffffff81133e18>] kthread+0x268/0x300 kernel/kthread.c:211
       [<ffffffff827066c5>] ret_from_fork+0x55/0x80 arch/x86/entry/entry_64.S:510

       [<ffffffff81202cde>] lock_acquire+0x15e/0x450 kernel/locking/lockdep.c:3592
       [<ffffffff826fad9b>] __mutex_lock_common kernel/locking/mutex.c:521 [inline]
       [<ffffffff826fad9b>] mutex_lock_nested+0xbb/0x8d0 kernel/locking/mutex.c:621
       [<ffffffff816c50c4>] ext4_register_li_request+0x304/0x7a0 fs/ext4/super.c:2961
       [<ffffffff816c68c8>] ext4_remount+0x1368/0x1bb0 fs/ext4/super.c:4911
       [<ffffffff8149bf58>] do_remount_sb2+0x428/0x7d0 fs/super.c:771
       [<ffffffff814fbe9e>] do_remount fs/namespace.c:2335 [inline]
       [<ffffffff814fbe9e>] do_mount+0x101e/0x2a10 fs/namespace.c:2848
       [<ffffffff814fe3e1>] SYSC_mount fs/namespace.c:3051 [inline]
       [<ffffffff814fe3e1>] SyS_mount+0x191/0x1c0 fs/namespace.c:3029
       [<ffffffff827062e1>] entry_SYSCALL_64_fastpath+0x1e/0x9a

       [<ffffffff81202cde>] lock_acquire+0x15e/0x450 kernel/locking/lockdep.c:3592
       [<ffffffff826fad9b>] __mutex_lock_common kernel/locking/mutex.c:521 [inline]
       [<ffffffff826fad9b>] mutex_lock_nested+0xbb/0x8d0 kernel/locking/mutex.c:621
       [<ffffffff816c4e47>] ext4_register_li_request+0x87/0x7a0 fs/ext4/super.c:2934
       [<ffffffff816c68c8>] ext4_remount+0x1368/0x1bb0 fs/ext4/super.c:4911
       [<ffffffff8149bf58>] do_remount_sb2+0x428/0x7d0 fs/super.c:771
       [<ffffffff814fbe9e>] do_remount fs/namespace.c:2335 [inline]
       [<ffffffff814fbe9e>] do_mount+0x101e/0x2a10 fs/namespace.c:2848
       [<ffffffff814fe3e1>] SYSC_mount fs/namespace.c:3051 [inline]
       [<ffffffff814fe3e1>] SyS_mount+0x191/0x1c0 fs/namespace.c:3029
       [<ffffffff827062e1>] entry_SYSCALL_64_fastpath+0x1e/0x9a

       [<ffffffff81202cde>] lock_acquire+0x15e/0x450 kernel/locking/lockdep.c:3592
       [<ffffffff82701312>] down_read+0x42/0x60 kernel/locking/rwsem.c:22
       [<ffffffff8149b671>] iterate_supers+0xe1/0x260 fs/super.c:537
       [<ffffffff8199e104>] selinux_complete_init+0x2f/0x31 security/selinux/hooks.c:6154
       [<ffffffff8198fd56>] security_load_policy+0x886/0x9b0 security/selinux/ss/services.c:2060
       [<ffffffff81965c81>] sel_write_load+0x191/0xfc0 security/selinux/selinuxfs.c:535
       [<ffffffff81490c1c>] __vfs_write+0x11c/0x3e0 fs/read_write.c:489
       [<ffffffff814928ce>] vfs_write+0x17e/0x4e0 fs/read_write.c:538
       [<ffffffff81494f09>] SYSC_write fs/read_write.c:585 [inline]
       [<ffffffff81494f09>] SyS_write+0xd9/0x1c0 fs/read_write.c:577
       [<ffffffff827062e1>] entry_SYSCALL_64_fastpath+0x1e/0x9a

       [<ffffffff81202cde>] lock_acquire+0x15e/0x450 kernel/locking/lockdep.c:3592
       [<ffffffff826fad9b>] __mutex_lock_common kernel/locking/mutex.c:521 [inline]
       [<ffffffff826fad9b>] mutex_lock_nested+0xbb/0x8d0 kernel/locking/mutex.c:621
       [<ffffffff81963767>] sel_commit_bools_write+0x87/0x250 security/selinux/selinuxfs.c:1142
       [<ffffffff81490c1c>] __vfs_write+0x11c/0x3e0 fs/read_write.c:489
       [<ffffffff81490fea>] __kernel_write+0x10a/0x350 fs/read_write.c:511
       [<ffffffff8152c05d>] write_pipe_buf+0x15d/0x1f0 fs/splice.c:1074
       [<ffffffff8152cef4>] splice_from_pipe_feed fs/splice.c:776 [inline]
       [<ffffffff8152cef4>] __splice_from_pipe+0x364/0x790 fs/splice.c:901
       [<ffffffff8152ffb9>] splice_from_pipe+0xf9/0x170 fs/splice.c:936
       [<ffffffff815300bc>] default_file_splice_write+0x3c/0x80 fs/splice.c:1086
       [<ffffffff81531181>] do_splice_from fs/splice.c:1128 [inline]
       [<ffffffff81531181>] do_splice fs/splice.c:1404 [inline]
       [<ffffffff81531181>] SYSC_splice fs/splice.c:1707 [inline]
       [<ffffffff81531181>] 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
       [<ffffffff82707a50>] sysenter_flags_fixed+0xd/0x1a

       [<ffffffff81202cde>] lock_acquire+0x15e/0x450 kernel/locking/lockdep.c:3592
       [<ffffffff826fad9b>] __mutex_lock_common kernel/locking/mutex.c:521 [inline]
       [<ffffffff826fad9b>] mutex_lock_nested+0xbb/0x8d0 kernel/locking/mutex.c:621
       [<ffffffff814aca0c>] __pipe_lock fs/pipe.c:86 [inline]
       [<ffffffff814aca0c>] fifo_open+0x15c/0x9e0 fs/pipe.c:896
       [<ffffffff8148ba0d>] do_dentry_open+0x38d/0xbd0 fs/open.c:749
       [<ffffffff8148f17a>] vfs_open+0x12a/0x210 fs/open.c:862
       [<ffffffff814bed5c>] do_last fs/namei.c:3222 [inline]
       [<ffffffff814bed5c>] path_openat+0x50c/0x39a0 fs/namei.c:3359
       [<ffffffff814c5e87>] do_filp_open+0x197/0x270 fs/namei.c:3393
       [<ffffffff814a1eef>] do_open_execat+0x10f/0x6f0 fs/exec.c:800
       [<ffffffff814a74a1>] do_execveat_common.isra.14+0x6a1/0x1f00 fs/exec.c:1573
       [<ffffffff814a9738>] compat_do_execve fs/exec.c:1706 [inline]
       [<ffffffff814a9738>] C_SYSC_execve fs/exec.c:1781 [inline]
       [<ffffffff814a9738>] compat_SyS_execve+0x48/0x60 fs/exec.c:1777
       [<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
       [<ffffffff82707a50>] sysenter_flags_fixed+0xd/0x1a

       [<ffffffff811ff0fc>] check_prev_add kernel/locking/lockdep.c:1853 [inline]
       [<ffffffff811ff0fc>] check_prevs_add kernel/locking/lockdep.c:1958 [inline]
       [<ffffffff811ff0fc>] validate_chain kernel/locking/lockdep.c:2144 [inline]
       [<ffffffff811ff0fc>] __lock_acquire+0x3e6c/0x5f10 kernel/locking/lockdep.c:3213
       [<ffffffff81202cde>] lock_acquire+0x15e/0x450 kernel/locking/lockdep.c:3592
       [<ffffffff826fbf4c>] __mutex_lock_common kernel/locking/mutex.c:521 [inline]
       [<ffffffff826fbf4c>] mutex_lock_killable_nested+0xcc/0xa10 kernel/locking/mutex.c:641
       [<ffffffff815dce1b>] do_io_accounting+0x1fb/0x7e0 fs/proc/base.c:2661
       [<ffffffff815dd422>] proc_tgid_io_accounting+0x22/0x30 fs/proc/base.c:2710
       [<ffffffff815daffd>] proc_single_show+0xfd/0x170 fs/proc/base.c:805
       [<ffffffff81501656>] seq_read+0x4b6/0x12b0 fs/seq_file.c:240
       [<ffffffff8149084c>] __vfs_read+0x11c/0x3d0 fs/read_write.c:432
       [<ffffffff81492520>] vfs_read+0x130/0x360 fs/read_write.c:454
       [<ffffffff81495135>] SYSC_pread64 fs/read_write.c:607 [inline]
       [<ffffffff81495135>] SyS_pread64+0x145/0x170 fs/read_write.c:594
       [<ffffffff810bf089>] sys32_pread+0x39/0x50 arch/x86/ia32/sys_ia32.c:179
       [<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
       [<ffffffff82707a50>] 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-executor0/16549:
 #0:  (&p->lock){+.+.+.}, at: [<ffffffff8150127d>] seq_read+0xdd/0x12b0 fs/seq_file.c:178

stack backtrace:
CPU: 1 PID: 16549 Comm: syz-executor0 Not tainted 4.4.162+ #7
 0000000000000000 a92ab1f675a1a7dd ffff8800b4d47608 ffffffff81a994bd
 ffffffff83ab4340 ffffffff83ab0170 ffffffff83aae820 ffff8801d7dae7e8
 ffff8801d7dadf00 ffff8800b4d47650 ffffffff813a834a 0000000000000001
Call Trace:
 [<ffffffff81a994bd>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81a994bd>] dump_stack+0xc1/0x124 lib/dump_stack.c:51
 [<ffffffff813a834a>] print_circular_bug.cold.34+0x2f7/0x432 kernel/locking/lockdep.c:1226
 [<ffffffff811ff0fc>] check_prev_add kernel/locking/lockdep.c:1853 [inline]
 [<ffffffff811ff0fc>] check_prevs_add kernel/locking/lockdep.c:1958 [inline]
 [<ffffffff811ff0fc>] validate_chain kernel/locking/lockdep.c:2144 [inline]
 [<ffffffff811ff0fc>] __lock_acquire+0x3e6c/0x5f10 kernel/locking/lockdep.c:3213
 [<ffffffff81202cde>] lock_acquire+0x15e/0x450 kernel/locking/lockdep.c:3592
 [<ffffffff826fbf4c>] __mutex_lock_common kernel/locking/mutex.c:521 [inline]
 [<ffffffff826fbf4c>] mutex_lock_killable_nested+0xcc/0xa10 kernel/locking/mutex.c:641
 [<ffffffff815dce1b>] do_io_accounting+0x1fb/0x7e0 fs/proc/base.c:2661
 [<ffffffff815dd422>] proc_tgid_io_accounting+0x22/0x30 fs/proc/base.c:2710
 [<ffffffff815daffd>] proc_single_show+0xfd/0x170 fs/proc/base.c:805
 [<ffffffff81501656>] seq_read+0x4b6/0x12b0 fs/seq_file.c:240
 [<ffffffff8149084c>] __vfs_read+0x11c/0x3d0 fs/read_write.c:432
 [<ffffffff81492520>] vfs_read+0x130/0x360 fs/read_write.c:454
 [<ffffffff81495135>] SYSC_pread64 fs/read_write.c:607 [inline]
 [<ffffffff81495135>] SyS_pread64+0x145/0x170 fs/read_write.c:594
 [<ffffffff810bf089>] sys32_pread+0x39/0x50 arch/x86/ia32/sys_ia32.c:179
 [<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
 [<ffffffff82707a50>] sysenter_flags_fixed+0xd/0x1a
audit: type=1400 audit(1540797495.701:179): avc:  denied  { create } for  pid=16525 comm="syz-executor5" 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(1540797495.741:180): avc:  denied  { setopt } for  pid=16525 comm="syz-executor5" 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
SELinux: security_validate_transition:  unrecognized class 0
SELinux: security_validate_transition:  unrecognized class 0
SELinux: security_validate_transition:  unrecognized class 0
SELinux: security_validate_transition:  unrecognized class 0
SELinux: security_validate_transition:  unrecognized class 0
SELinux: security_validate_transition:  unrecognized class 0
SELinux: security_validate_transition:  unrecognized class 0
device lo left promiscuous mode
SELinux: security_validate_transition:  unrecognized class 0
audit_printk_skb: 73 callbacks suppressed
audit: type=1400 audit(1540797498.421:205): avc:  denied  { create } for  pid=16670 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
audit: type=1400 audit(1540797498.541:206): avc:  denied  { create } for  pid=16685 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
audit: type=1400 audit(1540797499.281:207): avc:  denied  { create } for  pid=16700 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
audit: type=1400 audit(1540797499.321:208): avc:  denied  { relabelfrom } for  pid=16700 comm="syz-executor1" name="NETLINK" dev="sockfs" ino=52630 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(1540797499.351:209): avc:  denied  { relabelto } for  pid=16700 comm="syz-executor1" name="NETLINK" dev="sockfs" ino=52630 scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=system_u:object_r:vhost_device_t:s0 tclass=netlink_netfilter_socket permissive=1
SELinux: security_validate_transition:  unrecognized class 0
audit: type=1400 audit(1540797499.451:210): avc:  denied  { create } for  pid=16718 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
audit: type=1400 audit(1540797499.501:211): avc:  denied  { relabelfrom } for  pid=16718 comm="syz-executor1" name="NETLINK" dev="sockfs" ino=52162 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(1540797499.531:212): avc:  denied  { relabelto } for  pid=16718 comm="syz-executor1" name="NETLINK" dev="sockfs" ino=52162 scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=system_u:object_r:vhost_device_t:s0 tclass=netlink_netfilter_socket permissive=1
SELinux: security_validate_transition:  unrecognized class 0
audit: type=1400 audit(1540797500.131:213): avc:  denied  { create } for  pid=16725 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
audit: type=1400 audit(1540797500.191:214): avc:  denied  { relabelfrom } for  pid=16725 comm="syz-executor1" name="NETLINK" dev="sockfs" ino=52187 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
SELinux: security_validate_transition:  unrecognized class 0
audit_printk_skb: 3 callbacks suppressed
audit: type=1400 audit(1540797503.551:216): avc:  denied  { create } for  pid=16835 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
audit: type=1400 audit(1540797503.671:217): avc:  denied  { create } for  pid=16848 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
audit: type=1400 audit(1540797504.401:218): avc:  denied  { create } for  pid=16860 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