netdev - Re: [v2] ioctl: only memset non-NULL link settings

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Message-ID: <20200827103655.vyjtik4p23tzop4n@lion.mk-sys.cz>
Date:   Thu, 27 Aug 2020 12:36:55 +0200
From:   Michal Kubecek <mkubecek@...e.cz>
To:     Hans-Christian Noren Egtvedt <hegtvedt@...co.com>
Cc:     netdev@...r.kernel.org
Subject: Re: [v2] ioctl: only memset non-NULL link settings

On Thu, Aug 27, 2020 at 11:50:33AM +0200, Hans-Christian Noren Egtvedt wrote:
> In commit bef780467fa ('ioctl: do not pass transceiver value back to
> kernel') a regression slipped in. 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.
> 
> Fixes: bef780467fa7 ("ioctl: do not pass transceiver value back to kernel")
> Signed-off-by: Hans-Christian Noren Egtvedt <hegtvedt@...co.com>

Applied, thank you.

Michal

> ---
>  ethtool.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/ethtool.c b/ethtool.c
> index e32a93b..606af3e 100644
> --- a/ethtool.c
> +++ b/ethtool.c
> @@ -3048,10 +3048,11 @@ 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 == NULL)
>  			link_usettings = do_ioctl_gset(ctx);
> +		else
> +			memset(&link_usettings->deprecated, 0,
> +			       sizeof(link_usettings->deprecated));
>  		if (link_usettings == NULL) {
>  			perror("Cannot get current device settings");
>  			err = -1;
> -- 
> 2.25.1
> 

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