netdev - Re: [PATCH net v2] net: hdlc: In hdlc_rcv, check to make sure dev is an HDLC device

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Message-ID: <20201021173921.776d6250@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
Date:   Wed, 21 Oct 2020 17:39:21 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Xie He <xie.he.0141@...il.com>
Cc:     "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, Krzysztof Halasa <khc@...waw.pl>
Subject: Re: [PATCH net v2] net: hdlc: In hdlc_rcv, check to make sure dev
 is an HDLC device

On Mon, 19 Oct 2020 18:31:52 -0700 Xie He wrote:
> The hdlc_rcv function is used as hdlc_packet_type.func to process any
> skb received in the kernel with skb->protocol == htons(ETH_P_HDLC).
> The purpose of this function is to provide second-stage processing for
> skbs not assigned a "real" L3 skb->protocol value in the first stage.
> 
> This function assumes the device from which the skb is received is an
> HDLC device (a device created by this module). It assumes that
> netdev_priv(dev) returns a pointer to "struct hdlc_device".
> 
> However, it is possible that some driver in the kernel (not necessarily
> in our control) submits a received skb with skb->protocol ==
> htons(ETH_P_HDLC), from a non-HDLC device. In this case, the skb would
> still be received by hdlc_rcv. This will cause problems.
> 
> hdlc_rcv should be able to recognize and drop invalid skbs. It should
> first make sure "dev" is actually an HDLC device, before starting its
> processing. This patch adds this check to hdlc_rcv.
> 
> Cc: Krzysztof Halasa <khc@...waw.pl>
> Signed-off-by: Xie He <xie.he.0141@...il.com>

Applied, thank you!