netdev - Re: [PATCH] ioctl: only memset non-NULL link settings

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Message-ID: <20200827082304.ju7wsvf2xfego2a5@lion.mk-sys.cz>
Date:   Thu, 27 Aug 2020 10:23:04 +0200
From:   Michal Kubecek <mkubecek@...e.cz>
To:     Hans-Christian Noren Egtvedt <hegtvedt@...co.com>
Cc:     netdev@...r.kernel.org
Subject: Re: [PATCH] ioctl: only memset non-NULL link settings

On Mon, Aug 24, 2020 at 08:46:30AM +0200, Hans-Christian Noren Egtvedt wrote:
> In commit bef780467fa ('ioctl: do not pass transceiver value back to
> kernel') a regression slipped. If we have a kernel that does not support
> the ETHTOOL_xLINKSETTINGS API, then the do_ioctl_glinksettings()
> function will return a NULL pointer.
> 
> Hence before memset'ing the pointer to zero we must first check it is
> valid, as NULL return is perfectly fine when running on old kernels.
> 

Please add a standard "Fixes:" line here, i.e.

Fixes: bef780467fa7 ("ioctl: do not pass transceiver value back to kernel")

> Signed-off-by: Hans-Christian Noren Egtvedt <hegtvedt@...co.com>
> ---
>  ethtool.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/ethtool.c b/ethtool.c
> index c4ad186..8267d6b 100644
> --- a/ethtool.c
> +++ b/ethtool.c
> @@ -2908,8 +2908,10 @@ static int do_sset(struct cmd_context *ctx)
>  		struct ethtool_link_usettings *link_usettings;
>  
>  		link_usettings = do_ioctl_glinksettings(ctx);
> -		memset(&link_usettings->deprecated, 0,
> -		       sizeof(link_usettings->deprecated));
> +		if (link_usettings) {
> +			memset(&link_usettings->deprecated, 0,
> +			       sizeof(link_usettings->deprecated));
> +		}
>  		if (link_usettings == NULL)
>  			link_usettings = do_ioctl_gset(ctx);

This is correct fix but now we have two if statements with exactly
opposite conditions here; please combine them into one if-else.

Thank you,
Michal

>  		if (link_usettings == NULL) {
> -- 
> 2.25.1
> 

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