random: sshd: uninitialized urandom read (32 bytes read)
audit: type=1400 audit(1546208644.224:7): avc:  denied  { map } for  pid=1776 comm="syz-executor225" path="/root/syz-executor225115656" dev="sda1" ino=16481 scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:object_r:user_home_t:s0 tclass=file permissive=1

======================================================
WARNING: possible circular locking dependency detected
4.14.91+ #30 Not tainted
------------------------------------------------------
syz-executor225/1778 is trying to acquire lock:
 (&pipe->mutex/1){+.+.}, at: [<ffffffffb2379406>] __pipe_lock fs/pipe.c:88 [inline]
 (&pipe->mutex/1){+.+.}, at: [<ffffffffb2379406>] fifo_open+0x156/0x9d0 fs/pipe.c:921

but task is already holding lock:
 (&sig->cred_guard_mutex){+.+.}, at: [<ffffffffb237384e>] prepare_bprm_creds+0x4e/0x110 fs/exec.c:1389

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #1 (&sig->cred_guard_mutex){+.+.}:
       __mutex_lock_common kernel/locking/mutex.c:756 [inline]
       __mutex_lock+0xf5/0x1480 kernel/locking/mutex.c:893
       proc_pid_attr_write+0x16b/0x280 fs/proc/base.c:2590
       __vfs_write+0xf4/0x5c0 fs/read_write.c:482
       __kernel_write+0xf3/0x330 fs/read_write.c:503
       write_pipe_buf+0x192/0x250 fs/splice.c:797
       splice_from_pipe_feed fs/splice.c:502 [inline]
       __splice_from_pipe+0x324/0x740 fs/splice.c:626
       splice_from_pipe+0xcf/0x130 fs/splice.c:661
       default_file_splice_write+0x37/0x80 fs/splice.c:809
       do_splice_from fs/splice.c:851 [inline]
       do_splice fs/splice.c:1147 [inline]
       SYSC_splice fs/splice.c:1402 [inline]
       SyS_splice+0xd06/0x12a0 fs/splice.c:1382
       do_syscall_64+0x19b/0x4b0 arch/x86/entry/common.c:289
       entry_SYSCALL_64_after_hwframe+0x42/0xb7

-> #0 (&pipe->mutex/1){+.+.}:
       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
       __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:3455 [inline]
       path_openat+0x5f9/0x2930 fs/namei.c:3597
       do_filp_open+0x197/0x270 fs/namei.c:3631
       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

other info that might help us debug this:

 Possible unsafe locking scenario:

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

 *** DEADLOCK ***

1 lock held by syz-executor225/1778:
 #0:  (&sig->cred_guard_mutex){+.+.}, at: [<ffffffffb237384e>] prepare_bprm_creds+0x4e/0x110 fs/exec.c:1389

stack backtrace:
CPU: 1 PID: 1778 Comm: syz-executor225 Not tainted 4.14.91+ #30
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
 __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:3455 [inline]
 path_openat+0x5f9/0x2930 fs/namei.c:3597
 do_filp_open+0x197/0x270 fs/namei.c:3631
 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
RIP: 0033:0x445709
RSP: 002b:00007fcfa1e00da8 EFLAGS: 00000246 ORIG_RAX: 000000000000003b
RAX: ffffffffffffffda RBX: 000000000