======================================================
[ INFO: possible circular locking dependency detected ]
4.4.169+ #7 Not tainted
-------------------------------------------------------
syz-executor0/7541 is trying to acquire lock:
 (&sig->cred_guard_mutex){+.+.+.}, at: [<ffffffff815e3c54>] lock_trace+0x44/0xc0 fs/proc/base.c:448

but task is already holding lock:
 (&p->lock){+.+.+.}, at: [<ffffffff8150232d>] 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:

       [<ffffffff8120384e>] lock_acquire+0x15e/0x450 kernel/locking/lockdep.c:3592
       [<ffffffff82709ad2>] __mutex_lock_common kernel/locking/mutex.c:521 [inline]
       [<ffffffff82709ad2>] mutex_lock_nested+0xc2/0xb60 kernel/locking/mutex.c:621
       [<ffffffff8150232d>] seq_read+0xdd/0x12b0 fs/seq_file.c:178
       [<ffffffff815d972d>] proc_reg_read+0xfd/0x180 fs/proc/inode.c:202
       [<ffffffff81491e68>] do_loop_readv_writev+0x148/0x1e0 fs/read_write.c:680
       [<ffffffff81493ca1>] do_readv_writev+0x581/0x6f0 fs/read_write.c:810
       [<ffffffff81493e88>] vfs_readv+0x78/0xb0 fs/read_write.c:834
       [<ffffffff8153060f>] kernel_readv fs/splice.c:586 [inline]
       [<ffffffff8153060f>] default_file_splice_read+0x50f/0x8f0 fs/splice.c:662
       [<ffffffff8152c4e7>] do_splice_to+0xf7/0x140 fs/splice.c:1154
       [<ffffffff8152c772>] splice_direct_to_actor+0x242/0x830 fs/splice.c:1226
       [<ffffffff8152cf03>] do_splice_direct+0x1a3/0x270 fs/splice.c:1337
       [<ffffffff814950c4>] do_sendfile+0x4e4/0xb80 fs/read_write.c:1227
       [<ffffffff81497283>] C_SYSC_sendfile fs/read_write.c:1309 [inline]
       [<ffffffff81497283>] compat_SyS_sendfile+0x143/0x160 fs/read_write.c:1292
       [<ffffffff81006101>] do_syscall_32_irqs_on arch/x86/entry/common.c:330 [inline]
       [<ffffffff81006101>] do_fast_syscall_32+0x321/0xa80 arch/x86/entry/common.c:397
       [<ffffffff82717a90>] sysenter_flags_fixed+0xd/0x1a

       [<ffffffff8120384e>] lock_acquire+0x15e/0x450 kernel/locking/lockdep.c:3592
       [<ffffffff8149979e>] percpu_down_read include/linux/percpu-rwsem.h:26 [inline]
       [<ffffffff8149979e>] __sb_start_write+0x1ae/0x310 fs/super.c:1221
       [<ffffffff816bc127>] sb_start_write include/linux/fs.h:1517 [inline]
       [<ffffffff816bc127>] ext4_run_li_request fs/ext4/super.c:2674 [inline]
       [<ffffffff816bc127>] ext4_lazyinit_thread+0x1a7/0x750 fs/ext4/super.c:2773
       [<ffffffff811347f8>] kthread+0x268/0x300 kernel/kthread.c:211
       [<ffffffff82716705>] ret_from_fork+0x55/0x80 arch/x86/entry/entry_64.S:537

       [<ffffffff8120384e>] lock_acquire+0x15e/0x450 kernel/locking/lockdep.c:3592
       [<ffffffff82709ad2>] __mutex_lock_common kernel/locking/mutex.c:521 [inline]
       [<ffffffff82709ad2>] mutex_lock_nested+0xc2/0xb60 kernel/locking/mutex.c:621
       [<ffffffff816c6224>] ext4_register_li_request+0x304/0x7a0 fs/ext4/super.c:2961
       [<ffffffff816c7a28>] ext4_remount+0x1368/0x1bb0 fs/ext4/super.c:4911
       [<ffffffff8149ca48>] do_remount_sb2+0x428/0x7d0 fs/super.c:771
       [<ffffffff814fcf4e>] do_remount fs/namespace.c:2347 [inline]
       [<ffffffff814fcf4e>] do_mount+0x101e/0x2a10 fs/namespace.c:2860
       [<ffffffff814ff491>] SYSC_mount fs/namespace.c:3063 [inline]
       [<ffffffff814ff491>] SyS_mount+0x191/0x1c0 fs/namespace.c:3041
       [<ffffffff827162e1>] entry_SYSCALL_64_fastpath+0x1e/0x9a

       [<ffffffff8120384e>] lock_acquire+0x15e/0x450 kernel/locking/lockdep.c:3592
       [<ffffffff82709ad2>] __mutex_lock_common kernel/locking/mutex.c:521 [inline]
       [<ffffffff82709ad2>] mutex_lock_nested+0xc2/0xb60 kernel/locking/mutex.c:621
       [<ffffffff816c5fa7>] ext4_register_li_request+0x87/0x7a0 fs/ext4/super.c:2934
       [<ffffffff816c7a28>] ext4_remount+0x1368/0x1bb0 fs/ext4/super.c:4911
       [<ffffffff8149ca48>] do_remount_sb2+0x428/0x7d0 fs/super.c:771
       [  159.044549] audit: type=1400 audit(1545495471.081:29): avc:  denied  { create } for  pid=7540 comm="syz-executor3" 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=0
[<ffffffff814fcf4e>] do_remount fs/namespace.c:2347 [inline]
[<ffffffff814fcf4e>] do_mount+0x101e/0x2a10 fs/namespace.c:2860
       [<ffffffff814ff491>] SYSC_mount fs/namespace.c:3063 [inline]
       [<ffffffff814ff491>] SyS_mount+0x191/0x1c0 fs/namespace.c:3041
       [<ffffffff827162e1>] entry_SYSCALL_64_fastpath+0x1e/0x9a

       [<ffffffff8120384e>] lock_acquire+0x15e/0x450 kernel/locking/lockdep.c:3592
       [<ffffffff827112f2>] down_read+0x42/0x60 kernel/locking/rwsem.c:22
       [<ffffffff8149c161>] iterate_supers+0xe1/0x260 fs/super.c:537
       [<ffffffff819aaf49>] selinux_complete_init+0x2f/0x31 security/selinux/hooks.c:6154
       [<ffffffff8199cb96>] security_load_policy+0x886/0x9b0 security/selinux/ss/services.c:2060
       [<ffffffff81972ac1>] sel_write_load+0x191/0xfc0 security/selinux/selinuxfs.c:535
       [<ffffffff8149170c>] __vfs_write+0x11c/0x3e0 fs/read_write.c:489
       [<ffffffff814933be>] vfs_write+0x17e/0x4e0 fs/read_write.c:538
       [<ffffffff814959f9>] SYSC_write fs/read_write.c:585 [inline]
       [<ffffffff814959f9>] SyS_write+0xd9/0x1c0 fs/read_write.c:577
       [<ffffffff827162e1>] entry_SYSCALL_64_fastpath+0x1e/0x9a

       [<ffffffff8120384e>] lock_acquire+0x15e/0x450 kernel/locking/lockdep.c:3592
       [<ffffffff82709ad2>] __mutex_lock_common kernel/locking/mutex.c:521 [inline]
       [<ffffffff82709ad2>] mutex_lock_nested+0xc2/0xb60 kernel/locking/mutex.c:621
       [<ffffffff819705a7>] sel_commit_bools_write+0x87/0x250 security/selinux/selinuxfs.c:1142
       [<ffffffff8149170c>] __vfs_write+0x11c/0x3e0 fs/read_write.c:489
       [<ffffffff81491ada>] __kernel_write+0x10a/0x350 fs/read_write.c:511
       [<ffffffff8152d12d>] write_pipe_buf+0x15d/0x1f0 fs/splice.c:1074
       [<ffffffff8152dfc4>] splice_from_pipe_feed fs/splice.c:776 [inline]
       [<ffffffff8152dfc4>] __splice_from_pipe+0x364/0x790 fs/splice.c:901
       [<ffffffff81531089>] splice_from_pipe+0xf9/0x170 fs/splice.c:936
       [<ffffffff8153118c>] default_file_splice_write+0x3c/0x80 fs/splice.c:1086
       [<ffffffff81532251>] do_splice_from fs/splice.c:1128 [inline]
       [<ffffffff81532251>] do_splice fs/splice.c:1404 [inline]
       [<ffffffff81532251>] SYSC_splice fs/splice.c:1707 [inline]
       [<ffffffff81532251>] SyS_splice+0xde1/0x1430 fs/splice.c:1690
       [<ffffffff81006101>] do_syscall_32_irqs_on arch/x86/entry/common.c:330 [inline]
       [<ffffffff81006101>] do_fast_syscall_32+0x321/0xa80 arch/x86/entry/common.c:397
       [<ffffffff82717a90>] sysenter_flags_fixed+0xd/0x1a

       [<ffffffff8120384e>] lock_acquire+0x15e/0x450 kernel/locking/lockdep.c:3592
       [<ffffffff82709ad2>] __mutex_lock_common kernel/locking/mutex.c:521 [inline]
       [<ffffffff82709ad2>] mutex_lock_nested+0xc2/0xb60 kernel/locking/mutex.c:621
       [<ffffffff814ad4ec>] __pipe_lock fs/pipe.c:86 [inline]
       [<ffffffff814ad4ec>] fifo_open+0x15c/0x9e0 fs/pipe.c:896
       [<ffffffff8148c4fd>] do_dentry_open+0x38d/0xbd0 fs/open.c:749
       [<ffffffff8148fc6a>] vfs_open+0x12a/0x210 fs/open.c:862
       [<ffffffff814bff40>] do_last fs/namei.c:3269 [inline]
       [<ffffffff814bff40>] path_openat+0xc10/0x3f10 fs/namei.c:3406
       [<ffffffff814c6ed7>] do_filp_open+0x197/0x270 fs/namei.c:3440
       [<ffffffff814a29df>] do_open_execat+0x10f/0x6f0 fs/exec.c:805
       [<ffffffff814a7f81>] do_execveat_common.isra.14+0x6a1/0x1f00 fs/exec.c:1577
       [<ffffffff814aa218>] compat_do_execve fs/exec.c:1710 [inline]
       [<ffffffff814aa218>] C_SYSC_execve fs/exec.c:1785 [inline]
       [<ffffffff814aa218>] compat_SyS_execve+0x48/0x60 fs/exec.c:1781
       [<ffffffff81006101>] do_syscall_32_irqs_on arch/x86/entry/common.c:330 [inline]
       [<ffffffff81006101>] do_fast_syscall_32+0x321/0xa80 arch/x86/entry/common.c:397
       [<ffffffff82717a90>] sysenter_flags_fixed+0xd/0x1a

       [<ffffffff81200384>] check_prev_add kernel/locking/lockdep.c:1853 [inline]
       [<ffffffff81200384>] check_prevs_add kernel/locking/lockdep.c:1958 [inline]
       [<ffffffff81200384>] validate_chain kernel/locking/lockdep.c:2144 [inline]
       [<ffffffff81200384>] __lock_acquire+0x3cd4/0x5530 kernel/locking/lockdep.c:3213
       [<ffffffff8120384e>] lock_acquire+0x15e/0x450 kernel/locking/lockdep.c:3592
       [<ffffffff8270b1a2>] __mutex_lock_common kernel/locking/mutex.c:521 [inline]
       [<ffffffff8270b1a2>] mutex_lock_killable_nested+0xd2/0xce0 kernel/locking/mutex.c:641
       [<ffffffff815e3c54>] lock_trace+0x44/0xc0 fs/proc/base.c:448
       [<ffffffff815e3f7c>] proc_pid_personality+0x1c/0xc0 fs/proc/base.c:2854
       [<ffffffff815dc0fd>] proc_single_show+0xfd/0x170 fs/proc/base.c:805
       [<ffffffff81502706>] seq_read+0x4b6/0x12b0 fs/seq_file.c:240
       [<ffffffff81491e68>] do_loop_readv_writev+0x148/0x1e0 fs/read_write.c:680
       [<ffffffff814944f3>] compat_do_readv_writev+0x583/0x6f0 fs/read_write.c:984
       [<ffffffff8149473e>] compat_readv+0xde/0x150 fs/read_write.c:1013
       [<ffffffff814948f4>] __compat_sys_preadv64+0x144/0x170 fs/read_write.c:1054
       [<ffffffff81496c28>] C_SYSC_preadv fs/read_write.c:1074 [inline]
       [<ffffffff81496c28>] compat_SyS_preadv+0x38/0x50 fs/read_write.c:1068
       [<ffffffff81006101>] do_syscall_32_irqs_on arch/x86/entry/common.c:330 [inline]
       [<ffffffff81006101>] do_fast_syscall_32+0x321/0xa80 arch/x86/entry/common.c:397
       [<ffffffff82717a90>] 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-executor0/7541:
 #0:  (&p->lock){+.+.+.}, at: [<ffffffff8150232d>] seq_read+0xdd/0x12b0 fs/seq_file.c:178

stack backtrace:
CPU: 1 PID: 7541 Comm: syz-executor0 Not tainted 4.4.169+ #7
 0000000000000000 d6188528db02d9fd ffff8800b7cf75d0 ffffffff81aa635d
 ffffffff83ab8530 ffffffff83ab2860 ffff8801d96daf80 ffffffff83ab41b0
 ffff8801d96db868 ffff8800b7cf7620 ffffffff813a9589 ffff8801d96daf80
Call Trace:
 [<ffffffff81aa635d>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81aa635d>] dump_stack+0xc1/0x124 lib/dump_stack.c:51
 [<ffffffff813a9589>] print_circular_bug.cold.31+0x2f6/0x435 kernel/locking/lockdep.c:1226
 [<ffffffff81200384>] check_prev_add kernel/locking/lockdep.c:1853 [inline]
 [<ffffffff81200384>] check_prevs_add kernel/locking/lockdep.c:1958 [inline]
 [<ffffffff81200384>] validate_chain kernel/locking/lockdep.c:2144 [inline]
 [<ffffffff81200384>] __lock_acquire+0x3cd4/0x5530 kernel/locking/lockdep.c:3213
 [<ffffffff8120384e>] lock_acquire+0x15e/0x450 kernel/locking/lockdep.c:3592
 [<ffffffff8270b1a2>] __mutex_lock_common kernel/locking/mutex.c:521 [inline]
 [<ffffffff8270b1a2>] mutex_lock_killable_nested+0xd2/0xce0 kernel/locking/mutex.c:641
 [<ffffffff815e3c54>] lock_trace+0x44/0xc0 fs/proc/base.c:448
 [<ffffffff815e3f7c>] proc_pid_personality+0x1c/0xc0 fs/proc/base.c:2854
 [<ffffffff815dc0fd>] proc_single_show+0xfd/0x170 fs/proc/base.c:805
 [<ffffffff81502706>] seq_read+0x4b6/0x12b0 fs/seq_file.c:240
 [<ffffffff81491e68>] do_loop_readv_writev+0x148/0x1e0 fs/read_write.c:680
 [<ffffffff814944f3>] compat_do_readv_writev+0x583/0x6f0 fs/read_write.c:984
 [<ffffffff8149473e>] compat_readv+0xde/0x150 fs/read_write.c:1013
 [<ffffffff814948f4>] __compat_sys_preadv64+0x144/0x170 fs/read_write.c:1054
 [<ffffffff81496c28>] C_SYSC_preadv fs/read_write.c:1074 [inline]
 [<ffffffff81496c28>] compat_SyS_preadv+0x38/0x50 fs/read_write.c:1068
 [<ffffffff81006101>] do_syscall_32_irqs_on arch/x86/entry/common.c:330 [inline]
 [<ffffffff81006101>] do_fast_syscall_32+0x321/0xa80 arch/x86/entry/common.c:397
 [<ffffffff82717a90>] sysenter_flags_fixed+0xd/0x1a
audit_printk_skb: 6 callbacks suppressed
audit: type=1400 audit(1545495472.901:33): avc:  denied  { create } for  pid=7625 comm="syz-executor3" 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=0
audit: type=1400 audit(1545495472.861:32): avc:  denied  { create } for  pid=7619 comm="syz-executor0" 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=0
audit: type=1400 audit(1545495473.771:34): avc:  denied  { create } for  pid=7672 comm="syz-executor3" 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=0
audit: type=1400 audit(1545495473.801:35): avc:  denied  { create } for  pid=7673 comm="syz-executor0" 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=0
audit: type=1400 audit(1545495474.631:36): avc:  denied  { create } for  pid=7723 comm="syz-executor3" 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=0
audit: type=1400 audit(1545495474.701:37): avc:  denied  { create } for  pid=7724 comm="syz-executor0" 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=0
audit: type=1400 audit(1545495475.411:38): avc:  denied  { create } for  pid=7774 comm="syz-executor0" 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=0
audit: type=1400 audit(1545495475.421:39): avc:  denied  { create } for  pid=7772 comm="syz-executor3" 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=0
audit: type=1400 audit(1545495476.141:40): avc:  denied  { create } for  pid=7822 comm="syz-executor3" 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=0
audit: type=1400 audit(1545495476.301:41): avc:  denied  { create } for  pid=7832 comm="syz-executor0" 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=0
audit_printk_skb: 12 callbacks suppressed
audit: type=1400 audit(1545495478.041:46): avc:  denied  { create } for  pid=7918 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=0
audit: type=1400 audit(1545495478.111:47): avc:  denied  { create } for  pid=7918 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=0
audit: type=1400 audit(1545495478.191:48): avc:  denied  { create } for  pid=7917 comm="syz-executor3" 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=0
audit: type=1400 audit(1545495478.221:49): avc:  denied  { create } for  pid=7923 comm="syz-executor0" 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=0
audit: type=1400 audit(1545495479.171:50): avc:  denied  { create } for  pid=7966 comm="syz-executor3" 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=0
audit: type=1400 audit(1545495479.481:51): avc:  denied  { associate } for  pid=8008 comm="syz-executor5" name="uinput" dev="devtmpfs" ino=4373 scontext=system_u:object_r:setfiles_exec_t:s0 tcontext=system_u:object_r:device_t:s0 tclass=filesystem permissive=0
audit: type=1400 audit(1545495479.771:52): avc:  denied  { create } for  pid=8018 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=0
audit: type=1400 audit(1545495479.851:53): avc:  denied  { create } for  pid=8018 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=0
audit: type=1400 audit(1545495479.961:54): avc:  denied  { create } for  pid=8019 comm="syz-executor3" 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=0