[PATCH] enforce proper tlb flush in unmap_hugepage_range
Spotted by Hugh that hugetlb page is free'ed back to global pool before
performing any TLB flush in unmap_hugepage_range(). This potentially allow
threads to abuse free-alloc race condition.
The generic tlb gather code is unsuitable to use by hugetlb, I just open
coded a page gathering list and delayed put_page until tlb flush is
performed.
Cc: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Ken Chen <kenneth.w.chen@intel.com>
Acked-by: William Irwin <wli@holomorphy.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 7c7d03d..1d709ff 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -364,6 +364,8 @@
pte_t *ptep;
pte_t pte;
struct page *page;
+ struct page *tmp;
+ LIST_HEAD(page_list);
WARN_ON(!is_vm_hugetlb_page(vma));
BUG_ON(start & ~HPAGE_MASK);
@@ -384,12 +386,16 @@
continue;
page = pte_page(pte);
- put_page(page);
+ list_add(&page->lru, &page_list);
add_mm_counter(mm, file_rss, (int) -(HPAGE_SIZE / PAGE_SIZE));
}
spin_unlock(&mm->page_table_lock);
flush_tlb_range(vma, start, end);
+ list_for_each_entry_safe(page, tmp, &page_list, lru) {
+ list_del(&page->lru);
+ put_page(page);
+ }
}
static int hugetlb_cow(struct mm_struct *mm, struct vm_area_struct *vma,