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mm: Make copy_huge_page() always available

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Rewrite copy_huge_page() and move it into mm/util.c so it's always
available.  Fixes an exposure of uninitialised memory on configurations
with HUGETLB and UFFD enabled and MIGRATION disabled.

Fixes: 8cc5fcbb5b ("mm, hugetlb: fix racy resv_huge_pages underflow on UFFDIO_COPY")
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Matthew Wilcox (Oracle)
2021-07-12 16:32:07 +01:00
committed by Linus Torvalds
parent efdb6720b4
commit 79789db03f
4 changed files with 11 additions and 53 deletions
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48
mm/migrate.c
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@@ -536,54 +536,6 @@ int migrate_huge_page_move_mapping(struct address_space *mapping,
return MIGRATEPAGE_SUCCESS;
}
/*
* Gigantic pages are so large that we do not guarantee that page++ pointer
* arithmetic will work across the entire page. We need something more
* specialized.
*/
static void __copy_gigantic_page(struct page *dst, struct page *src,
int nr_pages)
{
int i;
struct page *dst_base = dst;
struct page *src_base = src;
for (i = 0; i < nr_pages; ) {
cond_resched();
copy_highpage(dst, src);
i++;
dst = mem_map_next(dst, dst_base, i);
src = mem_map_next(src, src_base, i);
}
}
void copy_huge_page(struct page *dst, struct page *src)
{
int i;
int nr_pages;
if (PageHuge(src)) {
/* hugetlbfs page */
struct hstate *h = page_hstate(src);
nr_pages = pages_per_huge_page(h);
if (unlikely(nr_pages > MAX_ORDER_NR_PAGES)) {
__copy_gigantic_page(dst, src, nr_pages);
return;
}
} else {
/* thp page */
BUG_ON(!PageTransHuge(src));
nr_pages = thp_nr_pages(src);
}
for (i = 0; i < nr_pages; i++) {
cond_resched();
copy_highpage(dst + i, src + i);
}
}
/*
* Copy the page to its new location
*/