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2024-02-20 102a0743326a03cd1a1202ceda21e175b7d3575c

 kernel/mm/frame_vector.c
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@@ -29,7 +29,11 @@
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  * different type underlying the specified range of virtual addresses.
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  * When the function isn't able to map a single page, it returns error.
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  *
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- * This function takes care of grabbing mmap_sem as necessary.
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+ * Note that get_vaddr_frames() cannot follow VM_IO mappings. It used
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+ * to be able to do that, but that could (racily) return non-refcounted
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+ * pfns.
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+ *
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+ * This function takes care of grabbing mmap_lock as necessary.
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  */
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 int get_vaddr_frames(unsigned long start, unsigned int nr_frames,
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 		     unsigned int gup_flags, struct frame_vector *vec)
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@@ -37,7 +41,6 @@
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 	struct mm_struct *mm = current->mm;
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 	struct vm_area_struct *vma;
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 	int ret = 0;
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-	int err;
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 	int locked;
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 	if (nr_frames == 0)
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@@ -48,7 +51,7 @@
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 	start = untagged_addr(start);
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-	down_read(&mm->mmap_sem);
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+	mmap_read_lock(mm);
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 	locked = 1;
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 	vma = find_vma_intersection(mm, start, start + 1);
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 	if (!vma) {
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@@ -72,37 +75,17 @@
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 	if (!(vma->vm_flags & (VM_IO | VM_PFNMAP))) {
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 		vec->got_ref = true;
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 		vec->is_pfns = false;
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-		ret = get_user_pages_locked(start, nr_frames,
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+		ret = pin_user_pages_locked(start, nr_frames,
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 			gup_flags, (struct page **)(vec->ptrs), &locked);
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-		goto out;
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+		if (likely(ret > 0))
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+			goto out;
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 	}
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-	vec->got_ref = false;
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-	vec->is_pfns = true;
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-	do {
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-		unsigned long *nums = frame_vector_pfns(vec);
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+	vec->nr_frames = 0;
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-		while (ret < nr_frames && start + PAGE_SIZE <= vma->vm_end) {
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-			err = follow_pfn(vma, start, &nums[ret]);
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-			if (err) {
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-				if (ret == 0)
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-					ret = err;
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-				goto out;
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-			}
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-			start += PAGE_SIZE;
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-			ret++;
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-		}
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-		/*
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-		 * We stop if we have enough pages or if VMA doesn't completely
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-		 * cover the tail page.
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-		 */
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-		if (ret >= nr_frames || start < vma->vm_end)
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-			break;
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-		vma = find_vma_intersection(mm, start, start + 1);
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-	} while (vma && vma->vm_flags & (VM_IO | VM_PFNMAP));
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 out:
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 	if (locked)
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-		up_read(&mm->mmap_sem);
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+		mmap_read_unlock(mm);
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 	if (!ret)
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 		ret = -EFAULT;
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 	if (ret > 0)
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@@ -122,7 +105,6 @@
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  */
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 void put_vaddr_frames(struct frame_vector *vec)
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 {
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-	int i;
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 	struct page **pages;
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 	if (!vec->got_ref)
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@@ -135,8 +117,8 @@
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 	 */
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 	if (WARN_ON(IS_ERR(pages)))
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 		goto out;
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-	for (i = 0; i < vec->nr_frames; i++)
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-		put_page(pages[i]);
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+
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+	unpin_user_pages(pages, vec->nr_frames);
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 	vec->got_ref = false;
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 out:
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 	vec->nr_frames = 0;