Hi all:
When I investigate the mm/hugetlb code, I found there's a possible data leak issue
with huge pmd sharing. Thank about the below scene:
1. Process A and process B shares huge pmd page.(vm_flags: VM_MAYSHARE but !VM_SHARED)
2. Process A write fault a hugetlb page. As vm_flags is !VM_SHARED, a private copy of
hugetlb page will be installed in the pagetable via hugetlb_wp.
3. Process A writes private data into hugetlb page.
4. Process B can read process A's private data since hugetlb page is shared through huge
pmd sharing...
I think the above scene is possible. If so, huge pmd sharing for !VM_SHARED should be disabled
to fix this issue? Or am I miss something about hugetlb huge pmd sharing?
Any response would be appreciated.
Thanks! :)
