======================================================
[ INFO: possible circular locking dependency detected ]
4.4.165+ #15 Not tainted
-------------------------------------------------------
syz-executor4/12552 is trying to acquire lock:
 (&sig->cred_guard_mutex){+.+.+.}, at: [<ffffffff815e35d4>] lock_trace+0x44/0xc0 fs/proc/base.c:448

but task is already holding lock:
 (&p->lock){+.+.+.}, at: [<ffffffff81501d0d>] 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:

       [<ffffffff8120370e>] lock_acquire+0x15e/0x450 kernel/locking/lockdep.c:3592
       [<ffffffff827078d2>] __mutex_lock_common kernel/locking/mutex.c:521 [inline]
       [<ffffffff827078d2>] mutex_lock_nested+0xc2/0xb60 kernel/locking/mutex.c:621
       [<ffffffff81501d0d>] seq_read+0xdd/0x12b0 fs/seq_file.c:178
       [<ffffffff815d90ad>] proc_reg_read+0xfd/0x180 fs/proc/inode.c:202
       [<ffffffff81491d98>] do_loop_readv_writev+0x148/0x1e0 fs/read_write.c:680
       [<ffffffff81493bd1>] do_readv_writev+0x581/0x6f0 fs/read_write.c:810
       [<ffffffff81493db8>] vfs_readv+0x78/0xb0 fs/read_write.c:834
       [<ffffffff8152ffef>] kernel_readv fs/splice.c:586 [inline]
       [<ffffffff8152ffef>] default_file_splice_read+0x50f/0x8f0 fs/splice.c:662
       [<ffffffff8152bec7>] do_splice_to+0xf7/0x140 fs/splice.c:1154
       [<ffffffff8152c152>] splice_direct_to_actor+0x242/0x830 fs/splice.c:1226
       [<ffffffff8152c8e3>] do_splice_direct+0x1a3/0x270 fs/splice.c:1337
       [<ffffffff81494ff4>] do_sendfile+0x4e4/0xb80 fs/read_write.c:1227
       [<ffffffff81497141>] C_SYSC_sendfile fs/read_write.c:1303 [inline]
       [<ffffffff81497141>] compat_SyS_sendfile+0xd1/0x160 fs/read_write.c:1292
       [<ffffffff810060fe>] do_syscall_32_irqs_on arch/x86/entry/common.c:330 [inline]
       [<ffffffff810060fe>] do_fast_syscall_32+0x31e/0xa80 arch/x86/entry/common.c:397
       [<ffffffff82715890>] sysenter_flags_fixed+0xd/0x1a

       [<ffffffff8120370e>] lock_acquire+0x15e/0x450 kernel/locking/lockdep.c:3592
       [<ffffffff814996ce>] percpu_down_read include/linux/percpu-rwsem.h:26 [inline]
       [<ffffffff814996ce>] __sb_start_write+0x1ae/0x310 fs/super.c:1221
       [<ffffffff816bba87>] sb_start_write include/linux/fs.h:1515 [inline]
       [<ffffffff816bba87>] ext4_run_li_request fs/ext4/super.c:2674 [inline]
       [<ffffffff816bba87>] ext4_lazyinit_thread+0x1a7/0x750 fs/ext4/super.c:2773
       [<ffffffff81134788>] kthread+0x268/0x300 kernel/kthread.c:211
       [<ffffffff82714505>] ret_from_fork+0x55/0x80 arch/x86/entry/entry_64.S:537

       [<ffffffff8120370e>] lock_acquire+0x15e/0x450 kernel/locking/lockdep.c:3592
       [<ffffffff827078d2>] __mutex_lock_common kernel/locking/mutex.c:521 [inline]
       [<ffffffff827078d2>] mutex_lock_nested+0xc2/0xb60 kernel/locking/mutex.c:621
       [<ffffffff816c5b84>] ext4_register_li_request+0x304/0x7a0 fs/ext4/super.c:2961
       [<ffffffff816c7388>] ext4_remount+0x1368/0x1bb0 fs/ext4/super.c:4911
       [<ffffffff8149c978>] do_remount_sb2+0x428/0x7d0 fs/super.c:771
       [<ffffffff814fc92e>] do_remount fs/namespace.c:2347 [inline]
       [<ffffffff814fc92e>] do_mount+0x101e/0x2a10 fs/namespace.c:2860
       [<ffffffff814fee71>] SYSC_mount fs/namespace.c:3063 [inline]
       [<ffffffff814fee71>] SyS_mount+0x191/0x1c0 fs/namespace.c:3041
       [<ffffffff827140e1>] entry_SYSCALL_64_fastpath+0x1e/0x9a

       [<ffffffff8120370e>] lock_acquire+0x15e/0x450 kernel/locking/lockdep.c:3592
       [<ffffffff827078d2>] __mutex_lock_common kernel/locking/mutex.c:521 [inline]
       [<ffffffff827078d2>] mutex_lock_nested+0xc2/0xb60 kernel/locking/mutex.c:621
       [<ffffffff816c5907>] ext4_register_li_request+0x87/0x7a0 fs/ext4/super.c:2934
       [<ffffffff816c7388>] ext4_remount+0x1368/0x1bb0 fs/ext4/super.c:4911
       [<ffffffff8149c978>] do_remount_sb2+0x428/0x7d0 fs/super.c:771
       [<ffffffff814fc92e>] do_remount fs/namespace.c:2347 [inline]
       [<ffffffff814fc92e>] do_mount+0x101e/0x2a10 fs/namespace.c:2860
       [<ffffffff814fee71>] SYSC_mount fs/namespace.c:3063 [inline]
       [<ffffffff814fee71>] SyS_mount+0x191/0x1c0 fs/namespace.c:3041
       [<ffffffff827140e1>] entry_SYSCALL_64_fastpath+0x1e/0x9a

       [<ffffffff8120370e>] lock_acquire+0x15e/0x450 kernel/locking/lockdep.c:3592
       [<ffffffff8270f0f2>] down_read+0x42/0x60 kernel/locking/rwsem.c:22
       [<ffffffff8149c091>] iterate_supers+0xe1/0x260 fs/super.c:537
       [<ffffffff819aa8e4>] selinux_complete_init+0x2f/0x31 security/selinux/hooks.c:6154
       [<ffffffff8199c536>] security_load_policy+0x886/0x9b0 security/selinux/ss/services.c:2060
       [<ffffffff81972461>] sel_write_load+0x191/0xfc0 security/selinux/selinuxfs.c:535
       [<ffffffff8149163c>] __vfs_write+0x11c/0x3e0 fs/read_write.c:489
       [<ffffffff814932ee>] vfs_write+0x17e/0x4e0 fs/read_write.c:538
       [<ffffffff81495929>] SYSC_write fs/read_write.c:585 [inline]
       [<ffffffff81495929>] SyS_write+0xd9/0x1c0 fs/read_write.c:577
       [<ffffffff827140e1>] entry_SYSCALL_64_fastpath+0x1e/0x9a

       [<ffffffff8120370e>] lock_acquire+0x15e/0x450 kernel/locking/lockdep.c:3592
       [<ffffffff827078d2>] __mutex_lock_common kernel/locking/mutex.c:521 [inline]
       [<ffffffff827078d2>] mutex_lock_nested+0xc2/0xb60 kernel/locking/mutex.c:621
       [<ffffffff8196ff47>] sel_commit_bools_write+0x87/0x250 security/selinux/selinuxfs.c:1142
       [<ffffffff8149163c>] __vfs_write+0x11c/0x3e0 fs/read_write.c:489
       [<ffffffff81491a0a>] __kernel_write+0x10a/0x350 fs/read_write.c:511
       [<ffffffff8152cb0d>] write_pipe_buf+0x15d/0x1f0 fs/splice.c:1074
       [<ffffffff8152d9a4>] splice_from_pipe_feed fs/splice.c:776 [inline]
       [<ffffffff8152d9a4>] __splice_from_pipe+0x364/0x790 fs/splice.c:901
       [<ffffffff81530a69>] splice_from_pipe+0xf9/0x170 fs/splice.c:936
       [<ffffffff81530b6c>] default_file_splice_write+0x3c/0x80 fs/splice.c:1086
       [<ffffffff81531c31>] do_splice_from fs/splice.c:1128 [inline]
       [<ffffffff81531c31>] do_splice fs/splice.c:1404 [inline]
       [<ffffffff81531c31>] SYSC_splice fs/splice.c:1707 [inline]
       [<ffffffff81531c31>] SyS_splice+0xde1/0x1430 fs/splice.c:1690
       [<ffffffff810060fe>] do_syscall_32_irqs_on arch/x86/entry/common.c:330 [inline]
       [<ffffffff810060fe>] do_fast_syscall_32+0x31e/0xa80 arch/x86/entry/common.c:397
       [<ffffffff82715890>] sysenter_flags_fixed+0xd/0x1a

       [<ffffffff8120370e>] lock_acquire+0x15e/0x450 kernel/locking/lockdep.c:3592
       [<ffffffff827078d2>] __mutex_lock_common kernel/locking/mutex.c:521 [inline]
       [<ffffffff827078d2>] mutex_lock_nested+0xc2/0xb60 kernel/locking/mutex.c:621
       [<ffffffff814ad42c>] __pipe_lock fs/pipe.c:86 [inline]
       [<ffffffff814ad42c>] fifo_open+0x15c/0x9e0 fs/pipe.c:896
       [<ffffffff8148c42d>] do_dentry_open+0x38d/0xbd0 fs/open.c:749
       [<ffffffff8148fb9a>] vfs_open+0x12a/0x210 fs/open.c:862
       [<ffffffff814bf77c>] do_last fs/namei.c:3222 [inline]
       [<ffffffff814bf77c>] path_openat+0x50c/0x39a0 fs/namei.c:3359
       [<ffffffff814c68a7>] do_filp_open+0x197/0x270 fs/namei.c:3393
       [<ffffffff814a290f>] do_open_execat+0x10f/0x6f0 fs/exec.c:800
       [<ffffffff814a7ec1>] do_execveat_common.isra.14+0x6a1/0x1f00 fs/exec.c:1573
       [<ffffffff814aa158>] compat_do_execve fs/exec.c:1706 [inline]
       [<ffffffff814aa158>] C_SYSC_execve fs/exec.c:1781 [inline]
       [<ffffffff814aa158>] compat_SyS_execve+0x48/0x60 fs/exec.c:1777
       [<ffffffff810060fe>] do_syscall_32_irqs_on arch/x86/entry/common.c:330 [inline]
       [<ffffffff810060fe>] do_fast_syscall_32+0x31e/0xa80 arch/x86/entry/common.c:397
       [<ffffffff82715890>] sysenter_flags_fixed+0xd/0x1a

       [<ffffffff81200244>] check_prev_add kernel/locking/lockdep.c:1853 [inline]
       [<ffffffff81200244>] check_prevs_add kernel/locking/lockdep.c:1958 [inline]
       [<ffffffff81200244>] validate_chain kernel/locking/lockdep.c:2144 [inline]
       [<ffffffff81200244>] __lock_acquire+0x3cd4/0x5530 kernel/locking/lockdep.c:3213
       [<ffffffff8120370e>] lock_acquire+0x15e/0x450 kernel/locking/lockdep.c:3592
       [<ffffffff82708fa2>] __mutex_lock_common kernel/locking/mutex.c:521 [inline]
       [<ffffffff82708fa2>] mutex_lock_killable_nested+0xd2/0xce0 kernel/locking/mutex.c:641
       [<ffffffff815e35d4>] lock_trace+0x44/0xc0 fs/proc/base.c:448
       [<ffffffff815e3e29>] proc_pid_syscall+0xa9/0x260 fs/proc/base.c:683
       [<ffffffff815dba7d>] proc_single_show+0xfd/0x170 fs/proc/base.c:805
       [<ffffffff815020e6>] seq_read+0x4b6/0x12b0 fs/seq_file.c:240
       [<ffffffff81491d98>] do_loop_readv_writev+0x148/0x1e0 fs/read_write.c:680
       [<ffffffff81493bd1>] do_readv_writev+0x581/0x6f0 fs/read_write.c:810
       [<ffffffff81493db8>] vfs_readv+0x78/0xb0 fs/read_write.c:834
       [<ffffffff8152ffef>] kernel_readv fs/splice.c:586 [inline]
       [<ffffffff8152ffef>] default_file_splice_read+0x50f/0x8f0 fs/splice.c:662
       [<ffffffff8152bec7>] do_splice_to+0xf7/0x140 fs/splice.c:1154
       [<ffffffff8152c152>] splice_direct_to_actor+0x242/0x830 fs/splice.c:1226
       [<ffffffff8152c8e3>] do_splice_direct+0x1a3/0x270 fs/splice.c:1337
       [<ffffffff81494ff4>] do_sendfile+0x4e4/0xb80 fs/read_write.c:1227
       [<ffffffff814971b3>] C_SYSC_sendfile fs/read_write.c:1309 [inline]
       [<ffffffff814971b3>] compat_SyS_sendfile+0x143/0x160 fs/read_write.c:1292
       [<ffffffff810060fe>] do_syscall_32_irqs_on arch/x86/entry/common.c:330 [inline]
       [<ffffffff810060fe>] do_fast_syscall_32+0x31e/0xa80 arch/x86/entry/common.c:397
       [<ffffffff82715890>] 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 ***

2 locks held by syz-executor4/12552:
 #0:  (sb_writers#7){.+.+.+}, at: [<ffffffff814953aa>] file_start_write include/linux/fs.h:2541 [inline]
 #0:  (sb_writers#7){.+.+.+}, at: [<ffffffff814953aa>] do_sendfile+0x89a/0xb80 fs/read_write.c:1226
 #1:  (&p->lock){+.+.+.}, at: [<ffffffff81501d0d>] seq_read+0xdd/0x12b0 fs/seq_file.c:178

stack backtrace:
CPU: 0 PID: 12552 Comm: syz-executor4 Not tainted 4.4.165+ #15
 0000000000000000 3e4d6b1f6bd4d407 ffff8800a7a26ce0 ffffffff81aa5c9d
 ffffffff83ab4380 ffffffff83aae860 ffff8801d6672f80 ffffffff83ab01b0
 ffff8801d6673890 ffff8800a7a26d30 ffffffff813a9479 ffff8801d6672f80
Call Trace:
 [<ffffffff81aa5c9d>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81aa5c9d>] dump_stack+0xc1/0x124 lib/dump_stack.c:51
 [<ffffffff813a9479>] print_circular_bug.cold.31+0x2f6/0x435 kernel/locking/lockdep.c:1226
 [<ffffffff81200244>] check_prev_add kernel/locking/lockdep.c:1853 [inline]
 [<ffffffff81200244>] check_prevs_add kernel/locking/lockdep.c:1958 [inline]
 [<ffffffff81200244>] validate_chain kernel/locking/lockdep.c:2144 [inline]
 [<ffffffff81200244>] __lock_acquire+0x3cd4/0x5530 kernel/locking/lockdep.c:3213
 [<ffffffff8120370e>] lock_acquire+0x15e/0x450 kernel/locking/lockdep.c:3592
 [<ffffffff82708fa2>] __mutex_lock_common kernel/locking/mutex.c:521 [inline]
 [<ffffffff82708fa2>] mutex_lock_killable_nested+0xd2/0xce0 kernel/locking/mutex.c:641
 [<ffffffff815e35d4>] lock_trace+0x44/0xc0 fs/proc/base.c:448
 [<ffffffff815e3e29>] proc_pid_syscall+0xa9/0x260 fs/proc/base.c:683
 [<ffffffff815dba7d>] proc_single_show+0xfd/0x170 fs/proc/base.c:805
 [<ffffffff815020e6>] seq_read+0x4b6/0x12b0 fs/seq_file.c:240
 [<ffffffff81491d98>] do_loop_readv_writev+0x148/0x1e0 fs/read_write.c:680
audit: type=1400 audit(1543409114.299:43): avc:  denied  { create } for  pid=12579 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_scsitransport_socket permissive=1
 [<ffffffff81493bd1>] do_readv_writev+0x581/0x6f0 fs/read_write.c:810
 [<ffffffff81493db8>] vfs_readv+0x78/0xb0 fs/read_write.c:834
 [<ffffffff8152ffef>] kernel_readv fs/splice.c:586 [inline]
 [<ffffffff8152ffef>] default_file_splice_read+0x50f/0x8f0 fs/splice.c:662
 [<ffffffff8152bec7>] do_splice_to+0xf7/0x140 fs/splice.c:1154
 [<ffffffff8152c152>] splice_direct_to_actor+0x242/0x830 fs/splice.c:1226
 [<ffffffff8152c8e3>] do_splice_direct+0x1a3/0x270 fs/splice.c:1337
 [<ffffffff81494ff4>] do_sendfile+0x4e4/0xb80 fs/read_write.c:1227
 [<ffffffff814971b3>] C_SYSC_sendfile fs/read_write.c:1309 [inline]
 [<ffffffff814971b3>] compat_SyS_sendfile+0x143/0x160 fs/read_write.c:1292
 [<ffffffff810060fe>] do_syscall_32_irqs_on arch/x86/entry/common.c:330 [inline]
 [<ffffffff810060fe>] do_fast_syscall_32+0x31e/0xa80 arch/x86/entry/common.c:397
 [<ffffffff82715890>] sysenter_flags_fixed+0xd/0x1a
binder: 12777:12778 ioctl c0306201 0 returned -14
binder: 12777:12785 got reply transaction with no transaction stack
binder: 12777:12785 transaction failed 29201/-71, size 0-0 line 2922
binder: 12777:12798 ioctl c0189436 20000040 returned -22
binder_alloc: binder_alloc_mmap_handler: 12777 20001000-20004000 already mapped failed -16
binder: BINDER_SET_CONTEXT_MGR already set
binder: 12777:12798 ioctl c0306201 0 returned -14
binder: 12777:12829 got reply transaction with no transaction stack
binder: 12777:12829 transaction failed 29201/-71, size 0-0 line 2922
binder: 12777:12785 ioctl 40046207 0 returned -16
binder: undelivered TRANSACTION_ERROR: 29201
binder: undelivered TRANSACTION_ERROR: 29201