linux-kernel - Re: [PATCH 1/1 v2] xen: set error code on failures

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Date:   Mon, 5 Dec 2016 09:58:50 +0100
From:   Juergen Gross <jgross@...e.com>
To:     Pan Bian <bianpan2016@....com>,
        David Vrabel <david.vrabel@...rix.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        xen-devel@...ts.xenproject.org
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1 v2] xen: set error code on failures

On 05/12/16 09:23, Pan Bian wrote:
> Variable rc is reset in the loop, and its value will be non-negative
> during the second and after repeat of the loop. If it fails to allocate
> memory then, it may return a non-negative integer, which indicates no
> error. This patch fixes the bug, assigning "-ENOMEM" to rc when
> kzalloc() or alloc_page() returns NULL, and removing the initialization
> of rc outside of the loop.
> 
> v1 is reviewed by: Juergen Gross <jgross@...e.com>

Not being a real problem in this case I prefer spelling out explicit
"Acked-by:" or "Reviewed-by:" tags myself.

So for this version you can have:

Reviewed-by: Juergen Gross <jgross@...e.com>


Juergen

> 
> Signed-off-by: Pan Bian <bianpan2016@....com>
> ---
>  drivers/xen/gntalloc.c | 9 ++++++---
>  1 file changed, 6 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/xen/gntalloc.c b/drivers/xen/gntalloc.c
> index 7a47c4c..1bf55a3 100644
> --- a/drivers/xen/gntalloc.c
> +++ b/drivers/xen/gntalloc.c
> @@ -127,18 +127,21 @@ static int add_grefs(struct ioctl_gntalloc_alloc_gref *op,
>  	struct gntalloc_gref *gref, *next;
>  
>  	readonly = !(op->flags & GNTALLOC_FLAG_WRITABLE);
> -	rc = -ENOMEM;
>  	for (i = 0; i < op->count; i++) {
>  		gref = kzalloc(sizeof(*gref), GFP_KERNEL);
> -		if (!gref)
> +		if (!gref) {
> +			rc = -ENOMEM;
>  			goto undo;
> +		}
>  		list_add_tail(&gref->next_gref, &queue_gref);
>  		list_add_tail(&gref->next_file, &queue_file);
>  		gref->users = 1;
>  		gref->file_index = op->index + i * PAGE_SIZE;
>  		gref->page = alloc_page(GFP_KERNEL|__GFP_ZERO);
> -		if (!gref->page)
> +		if (!gref->page) {
> +			rc = -ENOMEM;
>  			goto undo;
> +		}
>  
>  		/* Grant foreign access to the page. */
>  		rc = gnttab_grant_foreign_access(op->domid,
>