=====================================
WARNING: bad unlock balance detected!
5.6.0-next-20200407-syzkaller #0 Not tainted
-------------------------------------
syz-executor.4/7260 is trying to release lock (&mm->mmap_sem) at:
[<ffffffff81a01220>] __get_user_pages_locked mm/gup.c:1367 [inline]
[<ffffffff81a01220>] __get_user_pages_remote mm/gup.c:1832 [inline]
[<ffffffff81a01220>] __get_user_pages_remote+0x540/0x740 mm/gup.c:1807
but there are no more locks to release!

other info that might help us debug this:
no locks held by syz-executor.4/7260.

stack backtrace:
CPU: 1 PID: 7260 Comm: syz-executor.4 Not tainted 5.6.0-next-20200407-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x188/0x20d lib/dump_stack.c:118
 __lock_release kernel/locking/lockdep.c:4633 [inline]
 lock_release+0x586/0x800 kernel/locking/lockdep.c:4941
 up_read+0x78/0x750 kernel/locking/rwsem.c:1573
 __get_user_pages_locked mm/gup.c:1367 [inline]
 __get_user_pages_remote mm/gup.c:1832 [inline]
 __get_user_pages_remote+0x540/0x740 mm/gup.c:1807
 pin_user_pages_remote+0x67/0xa0 mm/gup.c:2898
 process_vm_rw_single_vec mm/process_vm_access.c:108 [inline]
 process_vm_rw_core.isra.0+0x423/0x940 mm/process_vm_access.c:218
 process_vm_rw+0x21f/0x240 mm/process_vm_access.c:286
 __do_sys_process_vm_writev mm/process_vm_access.c:308 [inline]
 __se_sys_process_vm_writev mm/process_vm_access.c:303 [inline]
 __x64_sys_process_vm_writev+0xdf/0x1b0 mm/process_vm_access.c:303
 do_syscall_64+0xf6/0x7d0 arch/x86/entry/common.c:295
 entry_SYSCALL_64_after_hwframe+0x49/0xb3
RIP: 0033:0x45c879
Code: ad b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 7b b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fda084abc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000137
RAX: ffffffffffffffda RBX: 00007fda084ac6d4 RCX: 000000000045c879
RDX: 0000000000000001 RSI: 0000000020c22000 RDI: 0000000000001026
RBP: 000000000076bfa0 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000020c22fa0 R11: 0000000000000246 R12: 00000000ffffffff
R13: 000000000000085d R14: 00000000004cb1ee R15: 000000000076bfac
------------[ cut here ]------------
DEBUG_RWSEMS_WARN_ON(tmp < 0): count = 0xffffffffffffff00, magic = 0xffff8880983f7678, owner = 0x3, curr 0xffff88808eb70440, list empty
WARNING: CPU: 1 PID: 7260 at kernel/locking/rwsem.c:1435 __up_read kernel/locking/rwsem.c:1435 [inline]
WARNING: CPU: 1 PID: 7260 at kernel/locking/rwsem.c:1435 up_read+0x5f5/0x750 kernel/locking/rwsem.c:1574