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mm/hugetlb: fix races when looking up a CONT-PTE/PMD size hugetlb page

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commit fac35ba763ed07ba93154c95ffc0c4a55023707f upstream.

On some architectures (like ARM64), it can support CONT-PTE/PMD size
hugetlb, which means it can support not only PMD/PUD size hugetlb (2M and
1G), but also CONT-PTE/PMD size(64K and 32M) if a 4K page size specified.

So when looking up a CONT-PTE size hugetlb page by follow_page(), it will
use pte_offset_map_lock() to get the pte entry lock for the CONT-PTE size
hugetlb in follow_page_pte().  However this pte entry lock is incorrect
for the CONT-PTE size hugetlb, since we should use huge_pte_lock() to get
the correct lock, which is mm->page_table_lock.

That means the pte entry of the CONT-PTE size hugetlb under current pte
lock is unstable in follow_page_pte(), we can continue to migrate or
poison the pte entry of the CONT-PTE size hugetlb, which can cause some
potential race issues, even though they are under the 'pte lock'.

For example, suppose thread A is trying to look up a CONT-PTE size hugetlb
page by move_pages() syscall under the lock, however antoher thread B can
migrate the CONT-PTE hugetlb page at the same time, which will cause
thread A to get an incorrect page, if thread A also wants to do page
migration, then data inconsistency error occurs.

Moreover we have the same issue for CONT-PMD size hugetlb in
follow_huge_pmd().

To fix above issues, rename the follow_huge_pmd() as follow_huge_pmd_pte()
to handle PMD and PTE level size hugetlb, which uses huge_pte_lock() to
get the correct pte entry lock to make the pte entry stable.

Mike said:

Support for CONT_PMD/_PTE was added with bb9dd3df8e ("arm64: hugetlb:
refactor find_num_contig()").  Patch series "Support for contiguous pte
hugepages", v4.  However, I do not believe these code paths were
executed until migration support was added with 5480280d3f ("arm64/mm:
enable HugeTLB migration for contiguous bit HugeTLB pages") I would go
with 5480280d3f for the Fixes: targe.

Link: https://lkml.kernel.org/r/635f43bdd85ac2615a58405da82b4d33c6e5eb05.1662017562.git.baolin.wang@linux.alibaba.com
Fixes: 5480280d3f ("arm64/mm: enable HugeTLB migration for contiguous bit HugeTLB pages")
Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Suggested-by: Mike Kravetz <mike.kravetz@oracle.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
[5.4: Fixup contextual diffs before pin_user_pages()]
Signed-off-by: Samuel Mendoza-Jonas <samjonas@amazon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Baolin Wang 2022-09-01 18:41:31 +08:00 committed by Greg Kroah-Hartman
parent 69d4f3baa6
commit 176ba4c19d
3 changed files with 30 additions and 19 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
include/linux/hugetlb.h
View File

@ -127,8 +127,8 @@ struct page *follow_huge_addr(struct mm_struct *mm, unsigned long address,
struct page *follow_huge_pd(struct vm_area_struct *vma,
unsigned long address, hugepd_t hpd,
int flags, int pdshift);
struct page *follow_huge_pmd(struct mm_struct *mm, unsigned long address,
pmd_t *pmd, int flags);
struct page *follow_huge_pmd_pte(struct vm_area_struct *vma, unsigned long address,
int flags);
struct page *follow_huge_pud(struct mm_struct *mm, unsigned long address,
pud_t *pud, int flags);
struct page *follow_huge_pgd(struct mm_struct *mm, unsigned long address,
@ -175,7 +175,7 @@ static inline void hugetlb_show_meminfo(void)
{
}
#define follow_huge_pd(vma, addr, hpd, flags, pdshift) NULL
#define follow_huge_pmd(mm, addr, pmd, flags) NULL
#define follow_huge_pmd_pte(vma, addr, flags) NULL
#define follow_huge_pud(mm, addr, pud, flags) NULL
#define follow_huge_pgd(mm, addr, pgd, flags) NULL
#define prepare_hugepage_range(file, addr, len) (-EINVAL)

13
mm/gup.c
View File

@ -188,6 +188,17 @@ static struct page *follow_page_pte(struct vm_area_struct *vma,
spinlock_t *ptl;
pte_t *ptep, pte;
/*
* Considering PTE level hugetlb, like continuous-PTE hugetlb on
* ARM64 architecture.
*/
if (is_vm_hugetlb_page(vma)) {
page = follow_huge_pmd_pte(vma, address, flags);
if (page)
return page;
return no_page_table(vma, flags);
}
retry:
if (unlikely(pmd_bad(*pmd)))
return no_page_table(vma, flags);
@ -333,7 +344,7 @@ static struct page *follow_pmd_mask(struct vm_area_struct *vma,
if (pmd_none(pmdval))
return no_page_table(vma, flags);
if (pmd_huge(pmdval) && vma->vm_flags & VM_HUGETLB) {
page = follow_huge_pmd(mm, address, pmd, flags);
page = follow_huge_pmd_pte(vma, address, flags);
if (page)
return page;
return no_page_table(vma, flags);

30
mm/hugetlb.c
View File

@ -5157,30 +5157,30 @@ follow_huge_pd(struct vm_area_struct *vma,
}
struct page * __weak
follow_huge_pmd(struct mm_struct *mm, unsigned long address,
pmd_t *pmd, int flags)
follow_huge_pmd_pte(struct vm_area_struct *vma, unsigned long address, int flags)
{
struct hstate *h = hstate_vma(vma);
struct mm_struct *mm = vma->vm_mm;
struct page *page = NULL;
spinlock_t *ptl;
pte_t pte;
pte_t *ptep, pte;
retry:
ptl = pmd_lockptr(mm, pmd);
spin_lock(ptl);
/*
* make sure that the address range covered by this pmd is not
* unmapped from other threads.
*/
if (!pmd_huge(*pmd))
goto out;
pte = huge_ptep_get((pte_t *)pmd);
ptep = huge_pte_offset(mm, address, huge_page_size(h));
if (!ptep)
return NULL;
ptl = huge_pte_lock(h, mm, ptep);
pte = huge_ptep_get(ptep);
if (pte_present(pte)) {
page = pmd_page(*pmd) + ((address & ~PMD_MASK) >> PAGE_SHIFT);
page = pte_page(pte) +
((address & ~huge_page_mask(h)) >> PAGE_SHIFT);
if (flags & FOLL_GET)
get_page(page);
} else {
if (is_hugetlb_entry_migration(pte)) {
spin_unlock(ptl);
__migration_entry_wait(mm, (pte_t *)pmd, ptl);
__migration_entry_wait(mm, ptep, ptl);
goto retry;
}
/*
@ -5188,7 +5188,7 @@ retry:
* follow_page_mask().
*/
}
out:
spin_unlock(ptl);
return page;
}