netdev - Re: [PATCH ethtool] Fix segfault with cable test and ./configure --disable-netlink

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Message-ID: <20200720001251.5nwf7nhcivl6b4yk@lion.mk-sys.cz>
Date:   Mon, 20 Jul 2020 02:12:51 +0200
From:   Michal Kubecek <mkubecek@...e.cz>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     netdev <netdev@...r.kernel.org>, Chris Healy <cphealy@...il.com>
Subject: Re: [PATCH ethtool] Fix segfault with cable test and ./configure
 --disable-netlink

On Fri, Jul 17, 2020 at 12:05:09AM +0200, Andrew Lunn wrote:
> When the netlink interface code is disabled, a stub version of
> netlink_run_handler() is used. This stub version needs to handle the
> case when there is no possibility for a command to fall back to the
> IOCTL call. The two cable tests commands have no such fallback, and if
> we don't handle this, ethtool tries to jump through a NULL pointer
> resulting in a segfault.
> 
> Reported-by: Chris Healy <cphealy@...il.com>
> Signed-off-by: Andrew Lunn <andrew@...n.ch>

Applied, thank you. I'll need to be more thorough with teseting the
--disable-netlink builds.

Michal

> ---
>  netlink/extapi.h | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/netlink/extapi.h b/netlink/extapi.h
> index c5bfde9..a35d5f2 100644
> --- a/netlink/extapi.h
> +++ b/netlink/extapi.h
> @@ -46,6 +46,12 @@ void nl_monitor_usage(void);
>  static inline void netlink_run_handler(struct cmd_context *ctx,
>  				       nl_func_t nlfunc, bool no_fallback)
>  {
> +	if (no_fallback) {
> +		fprintf(stderr,
> +			"Command requires kernel netlink support which is not "
> +			"enabled in this ethtool binary\n");
> +		exit(1);
> +	}
>  }
>  
>  static inline int nl_monitor(struct cmd_context *ctx)
> -- 
> 2.27.0
> 

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