Commit 4a705fef authored by Naoya Horiguchi's avatar Naoya Horiguchi Committed by Linus Torvalds
Browse files

hugetlb: fix copy_hugetlb_page_range() to handle migration/hwpoisoned entry 



There's a race between fork() and hugepage migration, as a result we try
to "dereference" a swap entry as a normal pte, causing kernel panic.
The cause of the problem is that copy_hugetlb_page_range() can't handle
"swap entry" family (migration entry and hwpoisoned entry) so let's fix
it.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: default avatarNaoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Acked-by: default avatarHugh Dickins <hughd@google.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: <stable@vger.kernel.org>	[2.6.37+]
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 13ace4d0

mm/hugetlb.c

+43 −28
Original line number Diff line number Diff line
@@ -2520,6 +2520,31 @@ static void set_huge_ptep_writable(struct vm_area_struct *vma, 
		update_mmu_cache(vma, address, ptep);

}



static int is_hugetlb_entry_migration(pte_t pte)

{

	swp_entry_t swp;



	if (huge_pte_none(pte) || pte_present(pte))

		return 0;

	swp = pte_to_swp_entry(pte);

	if (non_swap_entry(swp) && is_migration_entry(swp))

		return 1;

	else

		return 0;

}



static int is_hugetlb_entry_hwpoisoned(pte_t pte)

{

	swp_entry_t swp;



	if (huge_pte_none(pte) || pte_present(pte))

		return 0;

	swp = pte_to_swp_entry(pte);

	if (non_swap_entry(swp) && is_hwpoison_entry(swp))

		return 1;

	else

		return 0;

}



int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src,

			    struct vm_area_struct *vma)
@@ -2559,10 +2584,26 @@ int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src, 
		dst_ptl = huge_pte_lock(h, dst, dst_pte);

		src_ptl = huge_pte_lockptr(h, src, src_pte);

		spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING);

		if (!huge_pte_none(huge_ptep_get(src_pte))) {

		entry = huge_ptep_get(src_pte);

		if (huge_pte_none(entry)) { /* skip none entry */

			;

		} else if (unlikely(is_hugetlb_entry_migration(entry) ||

				    is_hugetlb_entry_hwpoisoned(entry))) {

			swp_entry_t swp_entry = pte_to_swp_entry(entry);



			if (is_write_migration_entry(swp_entry) && cow) {

				/*

				 * COW mappings require pages in both

				 * parent and child to be set to read.

				 */

				make_migration_entry_read(&swp_entry);

				entry = swp_entry_to_pte(swp_entry);

				set_huge_pte_at(src, addr, src_pte, entry);

			}

			set_huge_pte_at(dst, addr, dst_pte, entry);

		} else {

			if (cow)

				huge_ptep_set_wrprotect(src, addr, src_pte);

			entry = huge_ptep_get(src_pte);

			ptepage = pte_page(entry);

			get_page(ptepage);

			page_dup_rmap(ptepage);
@@ -2578,32 +2619,6 @@ int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src, 
	return ret;

}



static int is_hugetlb_entry_migration(pte_t pte)

{

	swp_entry_t swp;



	if (huge_pte_none(pte) || pte_present(pte))

		return 0;

	swp = pte_to_swp_entry(pte);

	if (non_swap_entry(swp) && is_migration_entry(swp))

		return 1;

	else

		return 0;

}



static int is_hugetlb_entry_hwpoisoned(pte_t pte)

{

	swp_entry_t swp;



	if (huge_pte_none(pte) || pte_present(pte))

		return 0;

	swp = pte_to_swp_entry(pte);

	if (non_swap_entry(swp) && is_hwpoison_entry(swp))

		return 1;

	else

		return 0;

}



void __unmap_hugepage_range(struct mmu_gather *tlb, struct vm_area_struct *vma,

			    unsigned long start, unsigned long end,

			    struct page *ref_page)

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