BUG: sleeping function called from invalid context at mm/memory.c:2007
in_atomic(): 0, irqs_disabled(): 0, non_block: 0, pid: 5913, name: cmp
preempt_count: 0, expected: 0
RCU nest depth: 1, expected: 0
2 locks held by cmp/5913:
 #0: ffff88801b8cc078 (&mm->mmap_lock){++++}-{4:4}, at: mmap_read_lock include/linux/mmap_lock.h:592 [inline]
 #0: ffff88801b8cc078 (&mm->mmap_lock){++++}-{4:4}, at: exit_mmap+0x124/0xa10 mm/mmap.c:1284
 #1: ffffffff8e7e5460 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:300 [inline]
 #1: ffffffff8e7e5460 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:838 [inline]
 #1: ffffffff8e7e5460 (rcu_read_lock){....}-{1:3}, at: __pte_offset_map+0x2f/0x310 mm/pgtable-generic.c:290
CPU: 3 UID: 0 PID: 5913 Comm: cmp 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
 __might_resched.cold+0x1ec/0x232 kernel/sched/core.c:9162
 zap_pmd_range mm/memory.c:2007 [inline]
 zap_pud_range mm/memory.c:2032 [inline]
 zap_p4d_range mm/memory.c:2053 [inline]
 __zap_vma_range+0x184b/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: 0033:0x7fedcf5c96c5
Code: Unable to access opcode bytes at 0x7fedcf5c969b.
RSP: 002b:00007ffd9f5f73c8 EFLAGS: 00000202 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 00007fedcf6cafe8 RCX: 00007fedcf5c96c5
RDX: 00000000000000e7 RSI: ffffffffffffff88 RDI: 0000000000000000
RBP: 0000000000000001 R08: 00007ffd9f5f7358 R09: 0000000000000000
R10: 00007ffd9f5f71f0 R11: 0000000000000202 R12: 0000000000000000
R13: 0000000000000000 R14: 00007fedcf6c9680 R15: 00007fedcf6cb000
 </TASK>

=============================
[ BUG: Invalid wait context ]
syzkaller #0 Tainted: G        W          
-----------------------------
cmp/5913 is trying to lock:
ffff88801b8cc078 (&mm->mmap_lock){++++}-{4:4}, at: mmap_write_lock include/linux/mmap_lock.h:536 [inline]
ffff88801b8cc078 (&mm->mmap_lock){++++}-{4:4}, at: exit_mmap+0x22c/0xa10 mm/mmap.c:1308
other info that might help us debug this:
context-{5:5}
1 lock held by cmp/5913:
 #0: ffffffff8e7e5460 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:300 [inline]
 #0: ffffffff8e7e5460 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:838 [inline]
 #0: ffffffff8e7e5460 (rcu_read_lock){....}-{1:3}, at: __pte_offset_map+0x2f/0x310 mm/pgtable-generic.c:290
stack backtrace:
CPU: 3 UID: 0 PID: 5913 Comm: cmp Tainted: G        W           syzkaller #0 PREEMPT(full) 
Tainted: [W]=WARN
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_lock_invalid_wait_context kernel/locking/lockdep.c:4830 [inline]
 check_wait_context kernel/locking/lockdep.c:4902 [inline]
 __lock_acquire+0xfa4/0x2630 kernel/locking/lockdep.c:5187
 lock_acquire kernel/locking/lockdep.c:5868 [inline]
 lock_acquire+0x1b1/0x370 kernel/locking/lockdep.c:5825
 down_write+0x8b/0x1f0 kernel/locking/rwsem.c:1625
 mmap_write_lock include/linux/mmap_lock.h:536 [inline]
 exit_mmap+0x22c/0xa10 mm/mmap.c:1308
 __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: 0033:0x7fedcf5c96c5
Code: Unable to access opcode bytes at 0x7fedcf5c969b.
RSP: 002b:00007ffd9f5f73c8 EFLAGS: 00000202 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 00007fedcf6cafe8 RCX: 00007fedcf5c96c5
RDX: 00000000000000e7 RSI: ffffffffffffff88 RDI: 0000000000000000
RBP: 0000000000000001 R08: 00007ffd9f5f7358 R09: 0000000000000000
R10: 00007ffd9f5f71f0 R11: 0000000000000202 R12: 0000000000000000
R13: 0000000000000000 R14: 00007fedcf6c9680 R15: 00007fedcf6cb000
 </TASK>