netlink: 8 bytes leftover after parsing attributes in process `syz-executor.3'.
======================================================
WARNING: possible circular locking dependency detected
4.14.111+ #50 Not tainted
SELinux: unrecognized netlink message: protocol=0 nlmsg_type=0 sclass=netlink_route_socket pig=28904 comm=syz-executor.0
------------------------------------------------------
syz-executor.1/28900 is trying to acquire lock:
 (&event->child_mutex){+.+.}, at: [<000000003acae2be>] perf_event_for_each_child+0x82/0x150 kernel/events/core.c:4687

but task is already holding lock:
 (&cpuctx_mutex){+.+.}, at: [<0000000018816586>] 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:

-> #8 (&cpuctx_mutex){+.+.}:

-> #7 (pmus_lock){+.+.}:

-> #6 (cpu_hotplug_lock.rw_sem){++++}:

-> #5 (&sb->s_type->i_mutex_key#10){+.+.}:

-> #4 (ashmem_mutex){+.+.}:

-> #3 (&mm->mmap_sem){++++}:

-> #2 (&sb->s_type->i_mutex_key#5){++++}:

-> #1 (event_mutex){+.+.}:

-> #0 (&event->child_mutex){+.+.}:

other info that might help us debug this:

Chain exists of:
  &event->child_mutex --> pmus_lock --> &cpuctx_mutex

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&cpuctx_mutex);
                               lock(pmus_lock);
                               lock(&cpuctx_mutex);
  lock(&event->child_mutex);

 *** DEADLOCK ***

1 lock held by syz-executor.1/28900:
 #0:  (&cpuctx_mutex){+.+.}, at: [<0000000018816586>] perf_event_ctx_lock_nested+0x14d/0x2c0 kernel/events/core.c:1240

stack backtrace:
CPU: 0 PID: 28900 Comm: syz-executor.1 Not tainted 4.14.111+ #50
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
SELinux: unrecognized netlink message: protocol=0 nlmsg_type=0 sclass=netlink_route_socket pig=28904 comm=syz-executor.0
SELinux: unrecognized netlink message: protocol=0 nlmsg_type=0 sclass=netlink_route_socket pig=28929 comm=syz-executor.0
SELinux: unrecognized netlink message: protocol=0 nlmsg_type=0 sclass=netlink_route_socket pig=28976 comm=syz-executor.5
SELinux: unrecognized netlink message: protocol=0 nlmsg_type=0 sclass=netlink_route_socket pig=28988 comm=syz-executor.0
SELinux: unrecognized netlink message: protocol=0 nlmsg_type=0 sclass=netlink_route_socket pig=29018 comm=syz-executor.5
SELinux: unrecognized netlink message: protocol=0 nlmsg_type=0 sclass=netlink_route_socket pig=29025 comm=syz-executor.0
SELinux: unrecognized netlink message: protocol=0 nlmsg_type=0 sclass=netlink_route_socket pig=29050 comm=syz-executor.5
SELinux: unrecognized netlink message: protocol=0 nlmsg_type=0 sclass=netlink_route_socket pig=29063 comm=syz-executor.5
SELinux: unrecognized netlink message: protocol=0 nlmsg_type=0 sclass=netlink_route_socket pig=29081 comm=syz-executor.0
selinux_nlmsg_perm: 2 callbacks suppressed
SELinux: unrecognized netlink message: protocol=0 nlmsg_type=0 sclass=netlink_route_socket pig=29153 comm=syz-executor.5
SELinux: unrecognized netlink message: protocol=0 nlmsg_type=0 sclass=netlink_route_socket pig=29185 comm=syz-executor.5
SELinux: unrecognized netlink message: protocol=0 nlmsg_type=0 sclass=netlink_route_socket pig=29220 comm=syz-executor.5
SELinux: unrecognized netlink message: protocol=0 nlmsg_type=0 sclass=netlink_route_socket pig=29321 comm=syz-executor.3