Subject: Re: [PATCH iproute2] iplink_vrf: Save device index from response for return code

From: Hangbin Liu <[email-masked]>
Date: Mon, 4 Jun 2018 09:11:13 +0800

On Fri, Jun 01, 2018 at 08:50:16AM -0700, [email-masked] wrote:
> From: David Ahern <[email-masked]>
> 
> A recent commit changed rtnl_talk_* to return the response message in
> allocated memory so callers need to free it. The change to name_is_vrf
> did not save the device index which is pointing to a struct inside the
> now allocated and freed memory resulting in garbage getting returned
> in some cases.
> 
> Fix by using a stack variable to save the return value and only set
> it to ifi->ifi_index after all checks are done and before the answer
> buffer is freed.
> 
> Fixes: 86bf43c7c2fdc ("lib/libnetlink: update rtnl_talk to support malloc buff at run time")
> Cc: Hangbin Liu <[email-masked]>
> Cc: Phil Sutter <[email-masked]>
> Signed-off-by: David Ahern <[email-masked]>
> ---
>  ip/iplink_vrf.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/ip/iplink_vrf.c b/ip/iplink_vrf.c
> index e9dd0df98412..6004bb4f305e 100644
> --- a/ip/iplink_vrf.c
> +++ b/ip/iplink_vrf.c
> @@ -191,6 +191,7 @@ int name_is_vrf(const char *name)
>  	struct rtattr *tb[IFLA_MAX+1];
>  	struct rtattr *li[IFLA_INFO_MAX+1];
>  	struct ifinfomsg *ifi;
> +	int ifindex = 0;
>  	int len;
>  
>  	addattr_l(&req.n, sizeof(req), IFLA_IFNAME, name, strlen(name) + 1);
> @@ -218,7 +219,8 @@ int name_is_vrf(const char *name)
>  	if (strcmp(RTA_DATA(li[IFLA_INFO_KIND]), "vrf"))
>  		goto out;
>  
> +	ifindex = ifi->ifi_index;
>  out:
>  	free(answer);
> -	return ifi->ifi_index;
> +	return ifindex;
>  }
> -- 
> 2.11.0
> 

Thanks for the fix.

Acked-by: Hangbin Liu <[email-masked]>