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Subject[RFC v4 12/20] mm/spf Protect vm_policy's changes against speculative pf
Date
Mark the VMA touched when policy changes are applied to it so that
speculative page fault will be aborted.

Signed-off-by: Laurent Dufour <ldufour@linux.vnet.ibm.com>
---
mm/mempolicy.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 13d32c25226c..5e44b3e69a0d 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -447,8 +447,11 @@ void mpol_rebind_mm(struct mm_struct *mm, nodemask_t *new)
struct vm_area_struct *vma;

down_write(&mm->mmap_sem);
- for (vma = mm->mmap; vma; vma = vma->vm_next)
+ for (vma = mm->mmap; vma; vma = vma->vm_next) {
+ write_seqcount_begin(&vma->vm_sequence);
mpol_rebind_policy(vma->vm_policy, new, MPOL_REBIND_ONCE);
+ write_seqcount_end(&vma->vm_sequence);
+ }
up_write(&mm->mmap_sem);
}

@@ -711,6 +714,7 @@ static int vma_replace_policy(struct vm_area_struct *vma,
if (IS_ERR(new))
return PTR_ERR(new);

+ write_seqcount_begin(&vma->vm_sequence);
if (vma->vm_ops && vma->vm_ops->set_policy) {
err = vma->vm_ops->set_policy(vma, new);
if (err)
@@ -719,10 +723,12 @@ static int vma_replace_policy(struct vm_area_struct *vma,

old = vma->vm_policy;
vma->vm_policy = new; /* protected by mmap_sem */
+ write_seqcount_end(&vma->vm_sequence);
mpol_put(old);

return 0;
err_out:
+ write_seqcount_end(&vma->vm_sequence);
mpol_put(new);
return err;
}
--
2.7.4
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