diff --git a/mm/gup.c b/mm/gup.c index 1611e73b1121..19f6a458683d 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -772,16 +772,17 @@ static struct page *follow_p4d_mask(struct vm_area_struct *vma, unsigned int flags, struct follow_page_context *ctx) { - p4d_t *p4d; + p4d_t *p4dp, p4d; - p4d = p4d_offset(pgdp, address); - if (p4d_none(*p4d)) + p4dp = p4d_offset(pgdp, address); + p4d = READ_ONCE(*p4dp); + if (p4d_none(p4d)) return no_page_table(vma, flags); - BUILD_BUG_ON(p4d_huge(*p4d)); - if (unlikely(p4d_bad(*p4d))) + BUILD_BUG_ON(p4d_huge(p4d)); + if (unlikely(p4d_bad(p4d))) return no_page_table(vma, flags); - return follow_pud_mask(vma, address, p4d, flags, ctx); + return follow_pud_mask(vma, address, p4dp, flags, ctx); } /**