======================================================
WARNING: possible circular locking dependency detected
4.14.76+ #20 Not tainted
------------------------------------------------------
syz-executor1/8706 is trying to acquire lock:
 (&sig->cred_guard_mutex){+.+.}, at: [<ffffffff9a09e8f7>] do_io_accounting+0x1d7/0x770 fs/proc/base.c:2731

but task is already holding lock:
 (&p->lock){+.+.}, at: [<ffffffff99fd0bb4>] seq_read+0xd4/0x11d0 fs/seq_file.c:165

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 (&p->lock){+.+.}:
       __mutex_lock_common kernel/locking/mutex.c:756 [inline]
       __mutex_lock+0xf5/0x1480 kernel/locking/mutex.c:893
       seq_read+0xd4/0x11d0 fs/seq_file.c:165
       proc_reg_read+0xef/0x170 fs/proc/inode.c:217
       do_loop_readv_writev fs/read_write.c:698 [inline]
       do_iter_read+0x3cc/0x580 fs/read_write.c:922
       vfs_readv+0xe6/0x150 fs/read_write.c:984
       kernel_readv fs/splice.c:361 [inline]
       default_file_splice_read+0x495/0x860 fs/splice.c:416
       do_splice_to+0x102/0x150 fs/splice.c:880
       do_splice fs/splice.c:1173 [inline]
       SYSC_splice fs/splice.c:1402 [inline]
       SyS_splice+0xf4d/0x12a0 fs/splice.c:1382
       do_syscall_64+0x19b/0x4b0 arch/x86/entry/common.c:289
       entry_SYSCALL_64_after_hwframe+0x42/0xb7

-> #1 (&pipe->mutex/1){+.+.}:
       __mutex_lock_common kernel/locking/mutex.c:756 [inline]
       __mutex_lock+0xf5/0x1480 kernel/locking/mutex.c:893
       __pipe_lock fs/pipe.c:88 [inline]
       fifo_open+0x156/0x9d0 fs/pipe.c:921
       do_dentry_open+0x426/0xda0 fs/open.c:764
       vfs_open+0x11c/0x210 fs/open.c:878
       do_last fs/namei.c:3408 [inline]
       path_openat+0x4eb/0x23a0 fs/namei.c:3550
       do_filp_open+0x197/0x270 fs/namei.c:3584
       do_open_execat+0x10d/0x5b0 fs/exec.c:849
       do_execveat_common.isra.14+0x6cb/0x1d60 fs/exec.c:1740
       do_execve fs/exec.c:1847 [inline]
       SYSC_execve fs/exec.c:1928 [inline]
       SyS_execve+0x34/0x40 fs/exec.c:1923
       do_syscall_64+0x19b/0x4b0 arch/x86/entry/common.c:289
       entry_SYSCALL_64_after_hwframe+0x42/0xb7

-> #0 (&sig->cred_guard_mutex){+.+.}:
       lock_acquire+0x10f/0x380 kernel/locking/lockdep.c:3991
       __mutex_lock_common kernel/locking/mutex.c:756 [inline]
       __mutex_lock+0xf5/0x1480 kernel/locking/mutex.c:893
       do_io_accounting+0x1d7/0x770 fs/proc/base.c:2731
       proc_single_show+0xf1/0x160 fs/proc/base.c:762
       traverse+0x32b/0x8a0 fs/seq_file.c:111
       seq_read+0xc94/0x11d0 fs/seq_file.c:192
       do_loop_readv_writev fs/read_write.c:698 [inline]
       do_iter_read+0x3cc/0x580 fs/read_write.c:922
       vfs_readv+0xe6/0x150 fs/read_write.c:984
       do_preadv+0x187/0x230 fs/read_write.c:1068
       do_syscall_64+0x19b/0x4b0 arch/x86/entry/common.c:289
       entry_SYSCALL_64_after_hwframe+0x42/0xb7

other info that might help us debug this:

Chain exists of:
  &sig->cred_guard_mutex --> &pipe->mutex/1 --> &p->lock

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&p->lock);
                               lock(&pipe->mutex/1);
                               lock(&p->lock);
  lock(&sig->cred_guard_mutex);

 *** DEADLOCK ***

1 lock held by syz-executor1/8706:
 #0:  (&p->lock){+.+.}, at: [<ffffffff99fd0bb4>] seq_read+0xd4/0x11d0 fs/seq_file.c:165

stack backtrace:
CPU: 0 PID: 8706 Comm: syz-executor1 Not tainted 4.14.76+ #20
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0xb9/0x11b lib/dump_stack.c:53
 print_circular_bug.isra.18.cold.43+0x2d3/0x40c kernel/locking/lockdep.c:1258
 check_prev_add kernel/locking/lockdep.c:1901 [inline]
 check_prevs_add kernel/locking/lockdep.c:2018 [inline]
 validate_chain kernel/locking/lockdep.c:2460 [inline]
 __lock_acquire+0x2ff9/0x4320 kernel/locking/lockdep.c:3487
 lock_acquire+0x10f/0x380 kernel/locking/lockdep.c:3991
 __mutex_lock_common kernel/locking/mutex.c:756 [inline]
 __mutex_lock+0xf5/0x1480 kernel/locking/mutex.c:893
 do_io_accounting+0x1d7/0x770 fs/proc/base.c:2731
 proc_single_show+0xf1/0x160 fs/proc/base.c:762
 traverse+0x32b/0x8a0 fs/seq_file.c:111
 seq_read+0xc94/0x11d0 fs/seq_file.c:192
 do_loop_readv_writev fs/read_write.c:698 [inline]
 do_iter_read+0x3cc/0x580 fs/read_write.c:922
 vfs_readv+0xe6/0x150 fs/read_write.c:984
 do_preadv+0x187/0x230 fs/read_write.c:1068
 do_syscall_64+0x19b/0x4b0 arch/x86/entry/common.c:289
 entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x457569
RSP: 002b:00007fd96af9cc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000127
RAX: ffffffffffffffda RBX: 0000000000000004 RCX: 0000000000457569
RDX: 00000000000001d0 RSI: 00000000200017c0 RDI: 0000000000000004
RBP: 000000000072bf00 R08: 0000000000000000 R09: 0000000000000000
R10: 000000001f000000 R11: 0000000000000246 R12: 00007fd96af9d6d4
R13: 00000000004c3088 R14: 00000000004d4a40 R15: 00000000ffffffff
tmpfs: Bad mount option ���p��ݏ�ԭ�d��?�]-7�&�L�alXX���i;A��%��{
tmpfs: Bad mount option ���p��ݏ�ԭ�d��?�]-7�&�L�alXX���i;A��%��{
binder: 8844:8846 ioctl 40106614 20000380 returned -22
binder: 8844:8846 ioctl 8904 20000280 returned -22
binder: 8844:8850 ioctl 40106614 20000380 returned -22
binder: 8844:8851 ioctl 8904 20000280 returned -22
binder: 8870:8878 ioctl 40106614 20000380 returned -22
binder: 8870:8878 ioctl 8904 20000280 returned -22
binder: 8897:8904 ioctl 40106614 20000380 returned -22
SELinux: unrecognized netlink message: protocol=9 nlmsg_type=258 sclass=netlink_audit_socket pig=8898 comm=syz-executor2
binder: 8897:8904 ioctl 8904 20000280 returned -22
SELinux: unrecognized netlink message: protocol=9 nlmsg_type=59584 sclass=netlink_audit_socket pig=8898 comm=syz-executor2
SELinux: unrecognized netlink message: protocol=9 nlmsg_type=680 sclass=netlink_audit_socket pig=8898 comm=syz-executor2
SELinux: unrecognized netlink message: protocol=9 nlmsg_type=9092 sclass=netlink_audit_socket pig=8898 comm=syz-executor2
SELinux: unrecognized netlink message: protocol=9 nlmsg_type=1417 sclass=netlink_audit_socket pig=8898 comm=syz-executor2
SELinux: unrecognized netlink message: protocol=9 nlmsg_type=10306 sclass=netlink_audit_socket pig=8898 comm=syz-executor2
SELinux: unrecognized netlink message: protocol=9 nlmsg_type=0 sclass=netlink_audit_socket pig=8898 comm=syz-executor2
SELinux: unrecognized netlink message: protocol=9 nlmsg_type=9364 sclass=netlink_audit_socket pig=8898 comm=syz-executor2
SELinux: unrecognized netlink message: protocol=9 nlmsg_type=9284 sclass=netlink_audit_socket pig=8898 comm=syz-executor2
SELinux: unrecognized netlink message: protocol=9 nlmsg_type=0 sclass=netlink_audit_socket pig=8898 comm=syz-executor2
audit: type=1400 audit(1539874885.902:53): avc:  denied  { relabelto } for  pid=9746 comm="syz-executor3" name="UNIX" dev="sockfs" ino=24348 scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=system_u:object_r:passwd_exec_t:s0 tclass=unix_stream_socket permissive=1
netlink: 12 bytes leftover after parsing attributes in process `syz-executor1'.
netlink: 12 bytes leftover after parsing attributes in process `syz-executor1'.
netlink: 20 bytes leftover after parsing attributes in process `syz-executor1'.
netlink: 20 bytes leftover after parsing attributes in process `syz-executor1'.
netlink: 24 bytes leftover after parsing attributes in process `syz-executor1'.
netlink: 24 bytes leftover after parsing attributes in process `syz-executor1'.
selinux_nlmsg_perm: 352 callbacks suppressed
SELinux: unrecognized netlink message: protocol=0 nlmsg_type=55056 sclass=netlink_route_socket pig=10002 comm=syz-executor1
SELinux: unrecognized netlink message: protocol=0 nlmsg_type=55056 sclass=netlink_route_socket pig=10019 comm=syz-executor1
netlink: 12 bytes leftover after parsing attributes in process `syz-executor1'.
netlink: 12 bytes leftover after parsing attributes in process `syz-executor1'.
SELinux: unrecognized netlink message: protocol=0 nlmsg_type=0 sclass=netlink_route_socket pig=10153 comm=syz-executor2
netlink: 12 bytes leftover after parsing attributes in process `syz-executor1'.
audit: type=1400 audit(1539874887.582:54): avc:  denied  { module_load } for  pid=10151 comm="syz-executor3" path="/selinux/avc/cache_threshold" dev="selinuxfs" ino=25 scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=system_u:object_r:security_t:s0 tclass=system permissive=1
netlink: 12 bytes leftover after parsing attributes in process `syz-executor1'.
SELinux: unrecognized netlink message: protocol=0 nlmsg_type=0 sclass=netlink_route_socket pig=10171 comm=syz-executor2
SELinux: unrecognized netlink message: protocol=0 nlmsg_type=59664 sclass=netlink_route_socket pig=10212 comm=syz-executor1
SELinux: unrecognized netlink message: protocol=0 nlmsg_type=8 sclass=netlink_route_socket pig=10329 comm=syz-executor2
SELinux: unrecognized netlink message: protocol=0 nlmsg_type=8 sclass=netlink_route_socket pig=10345 comm=syz-executor2
SELinux: unrecognized netlink message: protocol=0 nlmsg_type=8 sclass=netlink_route_socket pig=10386 comm=syz-executor2
SELinux: unrecognized netlink message: protocol=0 nlmsg_type=8 sclass=netlink_route_socket pig=10400 comm=syz-executor2