From 73ab9e34ff2f16be887ffbcea3e920336d3553dc Mon Sep 17 00:00:00 2001 From: Laurent Dufour Date: Tue, 17 Apr 2018 16:33:17 +0200 Subject: [PATCH] FROMLIST: mm: protect SPF handler against anon_vma changes The speculative page fault handler must be protected against anon_vma changes. This is because page_add_new_anon_rmap() is called during the speculative path. In addition, don't try speculative page fault if the VMA don't have an anon_vma structure allocated because its allocation should be protected by the mmap_sem. In __vma_adjust() when importer->anon_vma is set, there is no need to protect against speculative page faults since speculative page fault is aborted if the vma->anon_vma is not set. When calling page_add_new_anon_rmap() vma->anon_vma is necessarily valid since we checked for it when locking the pte and the anon_vma is removed once the pte is unlocked. So even if the speculative page fault handler is running concurrently with do_unmap(), as the pte is locked in unmap_region() - through unmap_vmas() - and the anon_vma unlinked later, because we check for the vma sequence counter which is updated in unmap_page_range() before locking the pte, and then in free_pgtables() so when locking the pte the change will be detected. Change-Id: I6c1f3b5c811d1ddd7b3f769082e8bbd40f5b52a0 Signed-off-by: Laurent Dufour Link: https://lore.kernel.org/lkml/1523975611-15978-12-git-send-email-ldufour@linux.vnet.ibm.com/ Bug: 161210518 Signed-off-by: Vinayak Menon --- mm/memory.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/mm/memory.c b/mm/memory.c index 2c8bfa345f40..649807cf0510 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -412,7 +412,9 @@ void free_pgtables(struct mmu_gather *tlb, struct vm_area_struct *vma, * Hide vma from rmap and truncate_pagecache before freeing * pgtables */ + vm_write_begin(vma); unlink_anon_vmas(vma); + vm_write_end(vma); unlink_file_vma(vma); if (is_vm_hugetlb_page(vma)) { @@ -426,7 +428,9 @@ void free_pgtables(struct mmu_gather *tlb, struct vm_area_struct *vma, && !is_vm_hugetlb_page(next)) { vma = next; next = vma->vm_next; + vm_write_begin(vma); unlink_anon_vmas(vma); + vm_write_end(vma); unlink_file_vma(vma); } free_pgd_range(tlb, addr, vma->vm_end,