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.
Signed-off-by: Laurent Dufour <ldufour@xxxxxxxxxxxxxxxxxx>
---
mm/memory.c | 13 ++++++++++---
1 file changed, 10 insertions(+), 3 deletions(-)
diff --git a/mm/memory.c b/mm/memory.c
index 519c28507a93..cb6906435ff5 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -587,7 +587,9 @@ void free_pgtables(struct mmu_gather *tlb, struct vm_area_struct *vma,
* Hide vma from rmap and truncate_pagecache before freeing
* pgtables
*/
+ write_seqcount_begin(&vma->vm_sequence);
unlink_anon_vmas(vma);
+ write_seqcount_end(&vma->vm_sequence);
unlink_file_vma(vma);
if (is_vm_hugetlb_page(vma)) {
@@ -601,7 +603,9 @@ void free_pgtables(struct mmu_gather *tlb, struct vm_area_struct *vma,
&& !is_vm_hugetlb_page(next)) {
vma = next;
next = vma->vm_next;
+ write_seqcount_begin(&vma->vm_sequence);
unlink_anon_vmas(vma);
+ write_seqcount_end(&vma->vm_sequence);
unlink_file_vma(vma);
}
free_pgd_range(tlb, addr, vma->vm_end,
@@ -2403,7 +2407,7 @@ static int wp_page_copy(struct vm_fault *vmf)
* thread doing COW.
*/
ptep_clear_flush_notify(vma, vmf->address, vmf->pte);
- page_add_new_anon_rmap(new_page, vma, vmf->address, false);
+ __page_add_new_anon_rmap(new_page, vma, vmf->address, false);
mem_cgroup_commit_charge(new_page, memcg, false, false);
lru_cache_add_active_or_unevictable(new_page, vma);
/*
@@ -2873,7 +2877,7 @@ int do_swap_page(struct vm_fault *vmf)
mem_cgroup_commit_charge(page, memcg, true, false);
activate_page(page);
} else { /* ksm created a completely new copy */
- page_add_new_anon_rmap(page, vma, vmf->address, false);
+ __page_add_new_anon_rmap(page, vma, vmf->address, false);
mem_cgroup_commit_charge(page, memcg, false, false);
lru_cache_add_active_or_unevictable(page, vma);
}
@@ -3015,7 +3019,7 @@ static int do_anonymous_page(struct vm_fault *vmf)
}
inc_mm_counter_fast(vma->vm_mm, MM_ANONPAGES);
- page_add_new_anon_rmap(page, vma, vmf->address, false);
+ __page_add_new_anon_rmap(page, vma, vmf->address, false);
mem_cgroup_commit_charge(page, memcg, false, false);
lru_cache_add_active_or_unevictable(page, vma);
setpte:
@@ -3940,6 +3944,9 @@ int handle_speculative_fault(struct mm_struct *mm, unsigned long address,
if (address < vma->vm_start || vma->vm_end <= address)
goto unlock;
+ if (unlikely(!vma->anon_vma))
+ goto unlock;
+
/*
* Huge pages are not yet supported.
*/
--
2.7.4
--
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