syzbot

=====================================
WARNING: bad unlock balance detected!
syzkaller #0 Not tainted
-------------------------------------
dhcpcd-run-hook/5886 is trying to release lock (rcu_read_lock) at:
[<ffffffff825b687c>] rcu_lock_release include/linux/rcupdate.h:310 [inline]
[<ffffffff825b687c>] rcu_read_unlock include/linux/rcupdate.h:869 [inline]
[<ffffffff825b687c>] pte_unmap include/linux/pgtable.h:117 [inline]
[<ffffffff825b687c>] zap_pte_range mm/memory.c:1948 [inline]
[<ffffffff825b687c>] zap_pmd_range mm/memory.c:2004 [inline]
[<ffffffff825b687c>] zap_pud_range mm/memory.c:2032 [inline]
[<ffffffff825b687c>] zap_p4d_range mm/memory.c:2053 [inline]
[<ffffffff825b687c>] __zap_vma_range+0x22dc/0x4bf0 mm/memory.c:2093
but there are no more locks to release!

other info that might help us debug this:
1 lock held by dhcpcd-run-hook/5886:
 #0: ffff88802b94b438 (&mm->mmap_lock){++++}-{4:4}, at: mmap_read_lock include/linux/mmap_lock.h:592 [inline]
 #0: ffff88802b94b438 (&mm->mmap_lock){++++}-{4:4}, at: exit_mmap+0x124/0xa10 mm/mmap.c:1284

stack backtrace:
CPU: 2 UID: 0 PID: 5886 Comm: dhcpcd-run-hook Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120
 print_unlock_imbalance_bug.part.0+0xfb/0x106 kernel/locking/lockdep.c:5298
 print_unlock_imbalance_bug kernel/locking/lockdep.c:5278 [inline]
 __lock_release kernel/locking/lockdep.c:5537 [inline]
 lock_release kernel/locking/lockdep.c:5889 [inline]
 lock_release+0x28d/0x310 kernel/locking/lockdep.c:5875
 rcu_lock_release include/linux/rcupdate.h:310 [inline]
 rcu_read_unlock include/linux/rcupdate.h:869 [inline]
 pte_unmap include/linux/pgtable.h:117 [inline]
 zap_pte_range mm/memory.c:1948 [inline]
 zap_pmd_range mm/memory.c:2004 [inline]
 zap_pud_range mm/memory.c:2032 [inline]
 zap_p4d_range mm/memory.c:2053 [inline]
 __zap_vma_range+0x22e1/0x4bf0 mm/memory.c:2093
 unmap_vmas+0x299/0x5f0 mm/memory.c:2162
 exit_mmap+0x1ef/0xa10 mm/mmap.c:1300
 __mmput+0x12a/0x410 kernel/fork.c:1178
 mmput+0x67/0x80 kernel/fork.c:1201
 exit_mm kernel/exit.c:581 [inline]
 do_exit+0x833/0x2a60 kernel/exit.c:963
 do_group_exit+0xd5/0x2a0 kernel/exit.c:1117
 __do_sys_exit_group kernel/exit.c:1128 [inline]
 __se_sys_exit_group kernel/exit.c:1126 [inline]
 __x64_sys_exit_group+0x3e/0x50 kernel/exit.c:1126
 x64_sys_call+0x102c/0x1530 arch/x86/include/generated/asm/syscalls_64.h:232
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x10b/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f4a27bab6c5
Code: Unable to access opcode bytes at 0x7f4a27bab69b.
RSP: 002b:00007ffe0faf6ed8 EFLAGS: 00000202 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 00007ffe0faf7104 RCX: 00007f4a27bab6c5
RDX: 00000000000000e7 RSI: ffffffffffffff88 RDI: 0000000000000000
RBP: 0000000000000003 R08: 00007ffe0faf6fd0 R09: 0000000000000002
R10: 0000000000000000 R11: 0000000000000202 R12: 0000000000000000
R13: 00007ffe0faf7210 R14: 00007f4a27dbb000 R15: 00005576e2150d98
 </TASK>
------------[ cut here ]------------
rrln < 0 || rrln > RCU_NEST_PMAX
WARNING: kernel/rcu/tree_plugin.h:443 at __rcu_read_unlock kernel/rcu/tree_plugin.h:443 [inline], CPU#2: dhcpcd-run-hook/5886
WARNING: kernel/rcu/tree_plugin.h:443 at __rcu_read_unlock+0x235/0x5e0 kernel/rcu/tree_plugin.h:430, CPU#2: dhcpcd-run-hook/5886
Modules linked in:
CPU: 2 UID: 0 PID: 5886 Comm: dhcpcd-run-hook Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
RIP: 0010:__rcu_read_unlock kernel/rcu/tree_plugin.h:443 [inline]
RIP: 0010:__rcu_read_unlock+0x235/0x5e0 kernel/rcu/tree_plugin.h:430
Code: 74 11 c7 45 58 01 00 00 00 bf 09 00 00 00 e8 d2 70 da ff e8 cd fd 22 00 9c 58 f6 c4 02 0f 85 dd 02 00 00 fb e9 57 fe ff ff 90 <0f> 0b 90 5b 5d 41 5c 41 5d 41 5e 41 5f c3 cc cc cc cc e8 a4 74 88
RSP: 0018:ffffc90003387778 EFLAGS: 00010286
RAX: 00000000ffffffff RBX: ffff888025320000 RCX: ffffffff81e8a36e
RDX: 0000000000000000 RSI: ffffffff8df30d5f RDI: ffff8880253204c4
RBP: 0000000000000004 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000080000000 R11: 0000000000000001 R12: ffff88802b94b9b8
R13: fffffbfff21b8360 R14: 0000000000000000 R15: 00007f4a27cba000
FS:  0000000000000000(0000) GS:ffff8880d64e7000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ffe0faf6018 CR3: 0000000037c7b000 CR4: 0000000000352ef0
Call Trace:
 <TASK>
 rcu_read_unlock include/linux/rcupdate.h:871 [inline]
 pte_unmap include/linux/pgtable.h:117 [inline]
 zap_pte_range mm/memory.c:1948 [inline]
 zap_pmd_range mm/memory.c:2004 [inline]
 zap_pud_range mm/memory.c:2032 [inline]
 zap_p4d_range mm/memory.c:2053 [inline]
 __zap_vma_range+0x22e6/0x4bf0 mm/memory.c:2093
 unmap_vmas+0x299/0x5f0 mm/memory.c:2162
 exit_mmap+0x1ef/0xa10 mm/mmap.c:1300
 __mmput+0x12a/0x410 kernel/fork.c:1178
 mmput+0x67/0x80 kernel/fork.c:1201
 exit_mm kernel/exit.c:581 [inline]
 do_exit+0x833/0x2a60 kernel/exit.c:963
 do_group_exit+0xd5/0x2a0 kernel/exit.c:1117
 __do_sys_exit_group kernel/exit.c:1128 [inline]
 __se_sys_exit_group kernel/exit.c:1126 [inline]
 __x64_sys_exit_group+0x3e/0x50 kernel/exit.c:1126
 x64_sys_call+0x102c/0x1530 arch/x86/include/generated/asm/syscalls_64.h:232
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x10b/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f4a27bab6c5
Code: Unable to access opcode bytes at 0x7f4a27bab69b.
RSP: 002b:00007ffe0faf6ed8 EFLAGS: 00000202 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 00007ffe0faf7104 RCX: 00007f4a27bab6c5
RDX: 00000000000000e7 RSI: ffffffffffffff88 RDI: 0000000000000000
RBP: 0000000000000003 R08: 00007ffe0faf6fd0 R09: 0000000000000002
R10: 0000000000000000 R11: 0000000000000202 R12: 0000000000000000
R13: 00007ffe0faf7210 R14: 00007f4a27dbb000 R15: 00005576e2150d98
 </TASK>