mm: initialize return of vm_insert_pages

From: Tom Rix <[email protected]>

clang static analysis reports a garbage return

In file included from mm/memory.c:84:
mm/memory.c:1612:2: warning: Undefined or garbage value returned to caller [core.uninitialized.UndefReturn]

        return err;
        ^~~~~~~~~~

The setting of err depends on a loop executing.
So initialize err.

...

Quoted 23 lines · On Fri, 3 Jul 2020 08:53:54 -0700 [email protected] wrote:

From: Tom Rix <[email protected]>

clang static analysis reports a garbage return

In file included from mm/memory.c:84:
mm/memory.c:1612:2: warning: Undefined or garbage value returned to caller [core.uninitialized.UndefReturn]

        return err;
        ^~~~~~~~~~

The setting of err depends on a loop executing.
So initialize err.

...

mm/memory.c +1 -1

@@ -1601,7 +1601,7 @@ int vm_insert_pages(struct vm_area_struct *vma, unsigned long addr,
 	return insert_pages(vma, addr, pages, num, vma->vm_page_prot);
 #else
 	unsigned long idx = 0, pgcount = *num;
-	int err;
+	int err = -EINVAL;
 

mm/memory.c int vm_insert_pages(struct vm_area_struct *vma, unsigned long addr, · line 1607

Quoted 2 lines

mm/memory.c +0 -0

 	for (; idx < pgcount; ++idx) {
 		err = vm_insert_page(vma, addr + (PAGE_SIZE * idx), pages[idx]);

If a caller were to ask vm_insert_pages() to insert zero pages, I suspect we should just return zero and set *num to zero.