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FROMLIST: mm: protect SPF handler against anon_vma changes

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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 <ldufour@linux.vnet.ibm.com>
Link: https://lore.kernel.org/lkml/1523975611-15978-12-git-send-email-ldufour@linux.vnet.ibm.com/
Bug: 161210518
Signed-off-by: Vinayak Menon <vinmenon@codeaurora.org>
This commit is contained in:
Laurent Dufour
2018-04-17 16:33:17 +02:00
committed by Suren Baghdasaryan
parent 0525756e6b
commit 73ab9e34ff
1 changed files with 4 additions and 0 deletions
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4
mm/memory.c
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@@ -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,