From cad7f613c4d010e1d0f05c9a4fb33c7ae40ba115 Mon Sep 17 00:00:00 2001 From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> Date: Wed, 12 Dec 2012 13:50:57 -0800 Subject: [PATCH] thp: change_huge_pmd(): make sure we don't try to make a page writable mprotect core never tries to make page writable using change_huge_pmd(). Let's add an assert that the assumption is true. It's important to be sure we will not make huge zero page writable. Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Andi Kleen <ak@linux.intel.com> Cc: "H. Peter Anvin" <hpa@linux.intel.com> Cc: Mel Gorman <mel@csn.ul.ie> Cc: David Rientjes <rientjes@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> --- mm/huge_memory.c | 1 + 1 file changed, 1 insertion(+) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index a959b3a4ddd5..7742fb36eb4d 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -1273,6 +1273,7 @@ int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, pmd_t entry; entry = pmdp_get_and_clear(mm, addr, pmd); entry = pmd_modify(entry, newprot); + BUG_ON(pmd_write(entry)); set_pmd_at(mm, addr, pmd, entry); spin_unlock(&vma->vm_mm->page_table_lock); ret = 1; -- 2.20.1