netdev - Re: [PATCH net-next] devlink: fix return of uninitialized variable err

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Date:   Sat, 9 Jan 2021 16:41:16 -0800
From:   Jakub Kicinski <kuba@...nel.org>
To:     wangyunjian <wangyunjian@...wei.com>
Cc:     <netdev@...r.kernel.org>, <davem@...emloft.net>,
        <jerry.lilijun@...wei.com>, <xudingke@...wei.com>
Subject: Re: [PATCH net-next] devlink: fix return of uninitialized variable
 err

On Fri, 8 Jan 2021 21:21:13 +0800 wangyunjian wrote:
> From: Yunjian Wang <wangyunjian@...wei.com>
> 
> There is a potential execution path in which variable err is
> returned without being properly initialized previously. Fix
> this by initializing variable err to 0.
> 
> Addresses-Coverity: ("Uninitialized scalar variable")
> Fixes: 1db64e8733f6 ("devlink: Add devlink formatted message (fmsg) API")
> Signed-off-by: Yunjian Wang <wangyunjian@...wei.com>

Fixes should generally be targeting net, not net-next.

I don't think this can trigger. 

Only devlink_nl_cmd_health_reporter_diagnose_doit() can call here, and
before it does it calls devlink_fmsg_obj_nest_start() and end(), so
there will at least be DEVLINK_ATTR_FMSG_OBJ_NEST_START to iterate over.

Please double check this analysis, and resend the patch with the commit
message updated to reflect this is not a bug fix and without the fixes
tag.

> diff --git a/net/core/devlink.c b/net/core/devlink.c
> index ee828e4b1007..470215cd60b5 100644
> --- a/net/core/devlink.c
> +++ b/net/core/devlink.c
> @@ -5699,7 +5699,7 @@ devlink_fmsg_prepare_skb(struct devlink_fmsg *fmsg, struct sk_buff *skb,
>  	struct devlink_fmsg_item *item;
>  	struct nlattr *fmsg_nlattr;
>  	int i = 0;
> -	int err;
> +	int err = 0;

Please order variable declaration lines longest to shortest.
err should be before i.

>  	fmsg_nlattr = nla_nest_start_noflag(skb, DEVLINK_ATTR_FMSG);
>  	if (!fmsg_nlattr)