syzbot

random: sshd: uninitialized urandom read (32 bytes read)
audit: type=1400 audit(1550407535.411:7): avc:  denied  { map } for  pid=1784 comm="syz-executor813" path="/root/syz-executor813874553" dev="sda1" ino=16482 scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:object_r:user_home_t:s0 tclass=file permissive=1
audit: type=1400 audit(1550407535.461:8): avc:  denied  { create } for  pid=1784 comm="syz-executor813" scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tclass=netlink_iscsi_socket permissive=1
======================================================
WARNING: possible circular locking dependency detected
4.14.101+ #14 Not tainted
------------------------------------------------------
syz-executor813/1784 is trying to acquire lock:
 (pmus_lock){+.+.}, at: [<ffffffff9e9e5793>] swevent_hlist_get kernel/events/core.c:7886 [inline]
 (pmus_lock){+.+.}, at: [<ffffffff9e9e5793>] perf_swevent_init+0x123/0x4e0 kernel/events/core.c:7946

but task is already holding lock:
 (&cpuctx_mutex/1){+.+.}, at: [<ffffffff9e9e8b2d>] perf_event_ctx_lock_nested+0x14d/0x2c0 kernel/events/core.c:1240

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 (&cpuctx_mutex/1){+.+.}:

-> #1 (&cpuctx_mutex){+.+.}:

-> #0 (pmus_lock){+.+.}:

other info that might help us debug this:

Chain exists of:
  pmus_lock --> &cpuctx_mutex --> &cpuctx_mutex/1

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&cpuctx_mutex/1);
                               lock(&cpuctx_mutex);
                               lock(&cpuctx_mutex/1);
  lock(pmus_lock);

 *** DEADLOCK ***

2 locks held by syz-executor813/1784:
 #0:  (&pmus_srcu){....}, at: [<ffffffff9e9f123d>] perf_event_alloc.part.0+0xadd/0x1e70 kernel/events/core.c:9621
 #1:  (&cpuctx_mutex/1){+.+.}, at: [<ffffffff9e9e8b2d>] perf_event_ctx_lock_nested+0x14d/0x2c0 kernel/events/core.c:1240

stack backtrace:
CPU: 0 PID: 1784 Comm: syz-executor813 Not tainted 4.14.101+ #14
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0xb9/0x10e lib/dump_stack.c:53
 print_circular_bug.isra.0.cold+0x2dc/0x425 kernel/locking/lockdep.c:1258