linux-kernel - [PATCH mmotm] mm: _install_special_mapping() apply VM_LOCKED_CLEAR

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Date:   Wed, 2 Mar 2022 17:38:05 -0800 (PST)
From:   Hugh Dickins <hughd@...gle.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
cc:     Vlastimil Babka <vbabka@...e.cz>, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org
Subject: [PATCH mmotm] mm: _install_special_mapping() apply
 VM_LOCKED_CLEAR_MASK

_install_special_mapping() adds the VM_SPECIAL bit VM_DONTEXPAND (and
never attempts to update locked_vm), so it ought to be consistent with
mmap_region() and mlock_fixup(), making sure not to add VM_LOCKED or
VM_LOCKONFAULT.  I doubt that this fixes any problem in practice: just
do it for consistency.

Signed-off-by: Hugh Dickins <hughd@...gle.com>
---
Noticed in doing mm/munlock series, but not needed as a part of that.

 mm/mmap.c | 1 +
 1 file changed, 1 insertion(+)

--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -3420,6 +3420,7 @@ static struct vm_area_struct *__install_special_mapping(
 	vma->vm_end = addr + len;
 
 	vma->vm_flags = vm_flags | mm->def_flags | VM_DONTEXPAND | VM_SOFTDIRTY;
+	vma->vm_flags &= VM_LOCKED_CLEAR_MASK;
 	vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
 
 	vma->vm_ops = ops;