linux-kernel - Re: [PATCH v2] mm: initialize return of vm_insert

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Message-Id: <20200703120436.4031b4ea23e28a3babca3d2d@linux-foundation.org>
Date:   Fri, 3 Jul 2020 12:04:36 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     trix@...hat.com
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] mm: initialize return of vm_insert_pages

On Fri,  3 Jul 2020 08:53:54 -0700 trix@...hat.com wrote:

> From: Tom Rix <trix@...hat.com>
> 
> 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.
>
> ...
>
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -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;
>  
>  	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.