hulk inclusion category: bugfix bugzilla: https://atomgit.com/openeuler/kernel/issues/10116 -------------------------------- In copy_huge_pmd(), the special huge PMD path unconditionally allocates a pgtable and deposits it to the destination PMD. However, the pgtable withdraw in zap_huge_pmd() is guarded by arch_needs_pgtable_deposit(), which returns false on x86. This asymmetry causes a 4KB pgtable page and an mm->nr_ptes counter increment to leak on every fork+zap cycle of a special huge PMD on x86. Guard the deposit for special huge PMD in copy_huge_pmd() with the same arch_needs_pgtable_deposit() check, matching what vmf_insert_pfn_pmd() already does at insertion time and what zap_huge_pmd() does at teardown. Fixes: 923e224a1246 ("mm: introduce remap_pfn_range_try_pmd() for PMD-level hugepage mapping") Signed-off-by: Jinjiang Tu <tujinjiang@huawei.com> --- mm/huge_memory.c | 14 +++++++++----- 1 file changed, 9 insertions(+), 5 deletions(-) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 805a903d8423..d423824dc67a 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -1834,9 +1834,11 @@ int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm, pmd = pmdp_get_lockless(src_pmd); if (unlikely(pmd_present(pmd) && pmd_special(pmd))) { - pgtable = pte_alloc_one(dst_mm); - if (unlikely(!pgtable)) - goto out; + if (arch_needs_pgtable_deposit(dst_vma)) { + pgtable = pte_alloc_one(dst_mm); + if (unlikely(!pgtable)) + goto out; + } dst_ptl = pmd_lock(dst_mm, dst_pmd); src_ptl = pmd_lockptr(src_mm, src_pmd); spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING); @@ -1854,8 +1856,10 @@ int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm, /* dax won't reach here, it will be intercepted at vma_needs_copy() */ VM_WARN_ON_ONCE(vma_is_dax(src_vma)); - mm_inc_nr_ptes(dst_mm); - pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable); + if (pgtable) { + mm_inc_nr_ptes(dst_mm); + pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable); + } goto set_pmd; } -- 2.43.0