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mm: protect VMA modifications using VMA sequence count

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The VMA sequence count has been introduced to allow fast detection of
VMA modification when running a page fault handler without holding
the mmap_sem.

This patch provides protection against the VMA modification done in :
	- madvise()
	- mpol_rebind_policy()
	- vma_replace_policy()
	- change_prot_numa()
	- mlock(), munlock()
	- mprotect()
	- mmap_region()
	- collapse_huge_page()
	- userfaultd registering services

In addition, VMA fields which will be read during the speculative fault
path needs to be written using WRITE_ONCE to prevent write to be split
and intermediate values to be pushed to other CPUs.

Change-Id: Ic36046b7254e538b6baf7144c50ae577ee7f2074
Signed-off-by: Laurent Dufour <[email protected]>
Patch-mainline: linux-mm @ Tue, 17 Apr 2018 16:33:15
[[email protected]: trivial merge conflict fixes]
Signed-off-by: Vinayak Menon <[email protected]>
[[email protected]: trivial merge conflict fixes]
Signed-off-by: Charan Teja Reddy <[email protected]>
This commit is contained in:
Laurent Dufour 2018-04-17 16:33:15 +02:00 • committed by Vinayak Menon
commit 06219e6c87
9 changed files with 94 additions and 41 deletions
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5
fs/proc/task_mmu.c
View file

@ -1277,8 +1277,11 @@ static ssize_t clear_refs_write(struct file *file, const char __user *buf,
goto out_mm;
}
for (vma = mm->mmap; vma; vma = vma->vm_next) {
vma->vm_flags &= ~VM_SOFTDIRTY;
vm_write_begin(vma);
WRITE_ONCE(vma->vm_flags,
vma->vm_flags & ~VM_SOFTDIRTY);
vma_set_page_prot(vma);
vm_write_end(vma);
}
downgrade_write(&mm->mmap_sem);
break;