linux-kernel - Re: [PATCH 5/5] [RFC] devlink: Fix uninitialized error code in devlink_fmsg_prepare

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Date:   Tue, 28 May 2019 14:40:08 +0000
From:   Eran Ben Elisha <eranbe@...lanox.com>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>,
        Igor Konopko <igor.j.konopko@...el.com>,
        David Howells <dhowells@...hat.com>,
        "Mohit P . Tahiliani" <tahiliani@...k.edu.in>,
        Takashi Sakamoto <o-takashi@...amocchi.jp>,
        Matias Bjorling <mb@...htnvm.io>,
        Jiri Pirko <jiri@...lanox.com>,
        "David S . Miller" <davem@...emloft.net>,
        Jamal Hadi Salim <jhs@...atatu.com>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Clemens Ladisch <clemens@...isch.de>,
        Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>, Joe Perches <joe@...ches.com>,
        Arnd Bergmann <arnd@...db.de>,
        Dan Carpenter <dan.carpenter@...cle.com>
CC:     "linux-block@...r.kernel.org" <linux-block@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-afs@...ts.infradead.org" <linux-afs@...ts.infradead.org>,
        "alsa-devel@...a-project.org" <alsa-devel@...a-project.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 5/5] [RFC] devlink: Fix uninitialized error code in
 devlink_fmsg_prepare_skb()



On 5/28/2019 5:24 PM, Geert Uytterhoeven wrote:
> With gcc 4.1:
> 
>      net/core/devlink.c: In function ‘devlink_fmsg_prepare_skb’:
>      net/core/devlink.c:4325: warning: ‘err’ may be used uninitialized in this function
> 
> Indeed, if the list has less than *start entries, an uninitialized error
> code will be returned.

The logic guarantees that start is smaller than the length of the list.
but I guess that the compiler can't detect that.

Reviewed-by: Eran Ben Elisha <eranbe@...lanox.com>

> 
> Fix this by preinitializing err to zero.
> 
> Fixes: 1db64e8733f65381 ("devlink: Add devlink formatted message (fmsg) API")
> Signed-off-by: Geert Uytterhoeven <geert@...ux-m68k.org>
> ---
> I don't know if this can really happen, and if this is the right fix.
> Perhaps err should be initialized to some valid error code instead?
> ---
>   net/core/devlink.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/net/core/devlink.c b/net/core/devlink.c
> index d43bc52b8840d76b..91377e4eae9a43c1 100644
> --- a/net/core/devlink.c
> +++ b/net/core/devlink.c
> @@ -4321,8 +4321,8 @@ devlink_fmsg_prepare_skb(struct devlink_fmsg *fmsg, struct sk_buff *skb,
>   {
>   	struct devlink_fmsg_item *item;
>   	struct nlattr *fmsg_nlattr;
> +	int err = 0;
>   	int i = 0;
> -	int err;
>   
>   	fmsg_nlattr = nla_nest_start_noflag(skb, DEVLINK_ATTR_FMSG);
>   	if (!fmsg_nlattr)
>