linux-kernel - Re: [PATCH net] ethtool: fix genlmsg_put() failure handling in ethnl_default

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Message-ID: <20200709115721.492dcf76@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
Date:   Thu, 9 Jul 2020 11:57:21 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Michal Kubecek <mkubecek@...e.cz>
Cc:     "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH net] ethtool: fix genlmsg_put() failure handling in
 ethnl_default_dumpit()

On Thu,  9 Jul 2020 12:11:50 +0200 (CEST) Michal Kubecek wrote:
> If the genlmsg_put() call in ethnl_default_dumpit() fails, we bail out
> without checking if we already have some messages in current skb like we do
> with ethnl_default_dump_one() failure later. Therefore if existing messages
> almost fill up the buffer so that there is not enough space even for
> netlink and genetlink header, we lose all prepared messages and return and
> error.
> 
> Rather than duplicating the skb->len check, move the genlmsg_put(),
> genlmsg_cancel() and genlmsg_end() calls into ethnl_default_dump_one().
> This is also more logical as all message composition will be in
> ethnl_default_dump_one() and only iteration logic will be left in
> ethnl_default_dumpit().
> 
> Fixes: 728480f12442 ("ethtool: default handlers for GET requests")
> Reported-by: Jakub Kicinski <kuba@...nel.org>
> Signed-off-by: Michal Kubecek <mkubecek@...e.cz>

Reviewed-by: Jakub Kicinski <kuba@...nel.org>