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-rw-r--r--mm/hugetlb.c25
1 files changed, 23 insertions, 2 deletions
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index e198831..19558df 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -2393,6 +2393,22 @@ void unmap_hugepage_range(struct vm_area_struct *vma, unsigned long start,
{
mutex_lock(&vma->vm_file->f_mapping->i_mmap_mutex);
__unmap_hugepage_range(vma, start, end, ref_page);
+ /*
+ * Clear this flag so that x86's huge_pmd_share page_table_shareable
+ * test will fail on a vma being torn down, and not grab a page table
+ * on its way out. We're lucky that the flag has such an appropriate
+ * name, and can in fact be safely cleared here. We could clear it
+ * before the __unmap_hugepage_range above, but all that's necessary
+ * is to clear it before releasing the i_mmap_mutex below.
+ *
+ * This works because in the contexts this is called, the VMA is
+ * going to be destroyed. It is not vunerable to madvise(DONTNEED)
+ * because madvise is not supported on hugetlbfs. The same applies
+ * for direct IO. unmap_hugepage_range() is only being called just
+ * before free_pgtables() so clearing VM_MAYSHARE will not cause
+ * surprises later.
+ */
+ vma->vm_flags &= ~VM_MAYSHARE;
mutex_unlock(&vma->vm_file->f_mapping->i_mmap_mutex);
}
@@ -2959,9 +2975,14 @@ void hugetlb_change_protection(struct vm_area_struct *vma,
}
}
spin_unlock(&mm->page_table_lock);
- mutex_unlock(&vma->vm_file->f_mapping->i_mmap_mutex);
-
+ /*
+ * Must flush TLB before releasing i_mmap_mutex: x86's huge_pmd_unshare
+ * may have cleared our pud entry and done put_page on the page table:
+ * once we release i_mmap_mutex, another task can do the final put_page
+ * and that page table be reused and filled with junk.
+ */
flush_tlb_range(vma, start, end);
+ mutex_unlock(&vma->vm_file->f_mapping->i_mmap_mutex);
}
int hugetlb_reserve_pages(struct inode *inode,