From: Peter Xu <peterx@redhat.com> mainline inclusion from mainline-v6.12-rc1 commit bc02afbd4d73c4424ea12a0c35fa96e27172e8cb category: feature bugzilla: https://gitee.com/src-openeuler/kernel/issues/ID4NL4 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=... -------------------------------- Teach the fork code to properly copy pfnmaps for pmd/pud levels. Pud is much easier, the write bit needs to be persisted though for writable and shared pud mappings like PFNMAP ones, otherwise a follow up write in either parent or child process will trigger a write fault. Do the same for pmd level. Link: https://lkml.kernel.org/r/20240826204353.2228736-8-peterx@redhat.com Signed-off-by: Peter Xu <peterx@redhat.com> Cc: Alexander Gordeev <agordeev@linux.ibm.com> Cc: Alex Williamson <alex.williamson@redhat.com> Cc: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com> Cc: Borislav Petkov <bp@alien8.de> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Christian Borntraeger <borntraeger@linux.ibm.com> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: David Hildenbrand <david@redhat.com> Cc: Gavin Shan <gshan@redhat.com> Cc: Gerald Schaefer <gerald.schaefer@linux.ibm.com> Cc: Heiko Carstens <hca@linux.ibm.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Jason Gunthorpe <jgg@nvidia.com> Cc: Matthew Wilcox <willy@infradead.org> Cc: Niklas Schnelle <schnelle@linux.ibm.com> Cc: Paolo Bonzini <pbonzini@redhat.com> Cc: Ryan Roberts <ryan.roberts@arm.com> Cc: Sean Christopherson <seanjc@google.com> Cc: Sven Schnelle <svens@linux.ibm.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vasily Gorbik <gor@linux.ibm.com> Cc: Will Deacon <will@kernel.org> Cc: Zi Yan <ziy@nvidia.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Yin Tirui <yintirui@huawei.com> --- mm/huge_memory.c | 29 ++++++++++++++++++++++++++--- 1 file changed, 26 insertions(+), 3 deletions(-) diff --git a/mm/huge_memory.c b/mm/huge_memory.c index fea2fc53f030..5acd2cd68d0b 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -1779,6 +1779,24 @@ int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm, pgtable_t pgtable = NULL; int ret = -ENOMEM; + pmd = pmdp_get_lockless(src_pmd); + if (unlikely(pmd_special(pmd))) { + dst_ptl = pmd_lock(dst_mm, dst_pmd); + src_ptl = pmd_lockptr(src_mm, src_pmd); + spin_lock_nested(src_ptl, SINGLE_DEPTH_NESTING); + /* + * No need to recheck the pmd, it can't change with write + * mmap lock held here. + * + * Meanwhile, making sure it's not a CoW VMA with writable + * mapping, otherwise it means either the anon page wrongly + * applied special bit, or we made the PRIVATE mapping be + * able to wrongly write to the backend MMIO. + */ + VM_WARN_ON_ONCE(is_cow_mapping(src_vma->vm_flags) && pmd_write(pmd)); + goto set_pmd; + } + /* Skip if can be re-fill on fault */ if (!vma_is_anonymous(dst_vma)) return 0; @@ -1861,7 +1879,9 @@ int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm, pmdp_set_wrprotect(src_mm, addr, src_pmd); if (!userfaultfd_wp(dst_vma)) pmd = pmd_clear_uffd_wp(pmd); - pmd = pmd_mkold(pmd_wrprotect(pmd)); + pmd = pmd_wrprotect(pmd); +set_pmd: + pmd = pmd_mkold(pmd); set_pmd_at(dst_mm, addr, dst_pmd, pmd); ret = 0; @@ -1950,8 +1970,11 @@ int copy_huge_pud(struct mm_struct *dst_mm, struct mm_struct *src_mm, * TODO: once we support anonymous pages, use * folio_try_dup_anon_rmap_*() and split if duplicating fails. */ - pudp_set_wrprotect(src_mm, addr, src_pud); - pud = pud_mkold(pud_wrprotect(pud)); + if (is_cow_mapping(vma->vm_flags) && pud_write(pud)) { + pudp_set_wrprotect(src_mm, addr, src_pud); + pud = pud_wrprotect(pud); + } + pud = pud_mkold(pud); set_pud_at(dst_mm, addr, dst_pud, pud); ret = 0; -- 2.43.0