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mm: hugetlb_vmemmap: fix a race between vmemmap pmd split 

The local variable @page in __split_vmemmap_huge_pmd() to obtain a pmd
page without holding page_table_lock may possiblely get the page table
page instead of a huge pmd page.

The effect may be in set_pte_at() since we may pass an invalid page
struct, if set_pte_at() wants to access the page struct (e.g. 
CONFIG_PAGE_TABLE_CHECK is enabled), it may crash the kernel.

So fix it.  And inline __split_vmemmap_huge_pmd() since it only has one
user.

Link: https://lkml.kernel.org/r/20230707033859.16148-1-songmuchun@bytedance.com
Fixes: d8d55f5616 ("mm: sparsemem: use page table lock to protect kernel pmd operations")
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Muchun Song 2023-07-07 11:38:59 +08:00 committed by Andrew Morton
parent c200a7119b
commit 3ce2c24cb6
1 changed files with 14 additions and 20 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

34
mm/hugetlb_vmemmap.c
View File

@ -36,14 +36,22 @@ struct vmemmap_remap_walk {
struct list_head *vmemmap_pages;
};
static int __split_vmemmap_huge_pmd(pmd_t *pmd, unsigned long start)
static int split_vmemmap_huge_pmd(pmd_t *pmd, unsigned long start)
{
pmd_t __pmd;
int i;
unsigned long addr = start;
struct page *page = pmd_page(*pmd);
pte_t *pgtable = pte_alloc_one_kernel(&init_mm);
struct page *head;
pte_t *pgtable;
spin_lock(&init_mm.page_table_lock);
head = pmd_leaf(*pmd) ? pmd_page(*pmd) : NULL;
spin_unlock(&init_mm.page_table_lock);
if (!head)
return 0;
pgtable = pte_alloc_one_kernel(&init_mm);
if (!pgtable)
return -ENOMEM;
@ -53,7 +61,7 @@ static int __split_vmemmap_huge_pmd(pmd_t *pmd, unsigned long start)
pte_t entry, *pte;
pgprot_t pgprot = PAGE_KERNEL;
entry = mk_pte(page + i, pgprot);
entry = mk_pte(head + i, pgprot);
pte = pte_offset_kernel(&__pmd, addr);
set_pte_at(&init_mm, addr, pte, entry);
}
@ -65,8 +73,8 @@ static int __split_vmemmap_huge_pmd(pmd_t *pmd, unsigned long start)
* be treated as indepdenent small pages (as they can be freed
* individually).
*/
if (!PageReserved(page))
split_page(page, get_order(PMD_SIZE));
if (!PageReserved(head))
split_page(head, get_order(PMD_SIZE));
/* Make pte visible before pmd. See comment in pmd_install(). */
smp_wmb();
@ -80,20 +88,6 @@ static int __split_vmemmap_huge_pmd(pmd_t *pmd, unsigned long start)
return 0;
}
static int split_vmemmap_huge_pmd(pmd_t *pmd, unsigned long start)
{
int leaf;
spin_lock(&init_mm.page_table_lock);
leaf = pmd_leaf(*pmd);
spin_unlock(&init_mm.page_table_lock);
if (!leaf)
return 0;
return __split_vmemmap_huge_pmd(pmd, start);
}
static void vmemmap_pte_range(pmd_t *pmd, unsigned long addr,
unsigned long end,
struct vmemmap_remap_walk *walk)