netdev - Re: [PATCH net-next] ethtool: always write dev in ethnl_parse_header_dev

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Date:   Wed, 15 Dec 2021 02:47:48 -0800
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Jakub Kicinski <kuba@...nel.org>, davem@...emloft.net
Cc:     netdev@...r.kernel.org
Subject: Re: [PATCH net-next] ethtool: always write dev in
 ethnl_parse_header_dev_get


On 12/14/21 7:47 AM, Jakub Kicinski wrote:
> Commit 0976b888a150 ("ethtool: fix null-ptr-deref on ref tracker")
> made the write to req_info.dev conditional, but as Eric points out
> in a different follow up the structure is often allocated on the
> stack and not kzalloc()'d so seems safer to always write the dev,
> in case it's garbage on input.
>
> Signed-off-by: Jakub Kicinski <kuba@...nel.org>

Yep, this was basically how I wanted to fix this.


Reviewed-by: Eric Dumazet <edumazet@...gle.com>


> ---
>   net/ethtool/netlink.c | 5 ++---
>   1 file changed, 2 insertions(+), 3 deletions(-)
>
> diff --git a/net/ethtool/netlink.c b/net/ethtool/netlink.c
> index 767fb3f17267..f09c62302a9a 100644
> --- a/net/ethtool/netlink.c
> +++ b/net/ethtool/netlink.c
> @@ -141,10 +141,9 @@ int ethnl_parse_header_dev_get(struct ethnl_req_info *req_info,
>   		return -EINVAL;
>   	}
>   
> -	if (dev) {
> -		req_info->dev = dev;
> +	req_info->dev = dev;
> +	if (dev)
>   		netdev_tracker_alloc(dev, &req_info->dev_tracker, GFP_KERNEL);
> -	}
>   	req_info->flags = flags;
>   	return 0;
>   }