From: Jakub Kicinski <kuba@kernel.org>
To: "Bjørn Mork" <bjorn@mork.no>,
"Kristian Evensen" <kristian.evensen@gmail.com>
Cc: netdev@vger.kernel.org, subashab@codeaurora.org
Subject: Re: [PATCH net] qmi_wwan: Clone the skb when in pass-through mode
Date: Mon, 14 Jun 2021 13:05:30 -0700 [thread overview]
Message-ID: <20210614130530.7a422f27@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com> (raw)
In-Reply-To: <8735tky064.fsf@miraculix.mork.no>
On Mon, 14 Jun 2021 16:45:55 +0200 Bjørn Mork wrote:
> Kristian Evensen <kristian.evensen@gmail.com> writes:
>
> > The skb that we pass to the rmnet driver is owned by usbnet and is freed
> > soon after the rx_fixup() callback is called (in usbnet_bh()). There is
> > no guarantee that rmnet is done handling the skb before it is freed. We
> > should clone the skb before we call netif_rx() to prevent use-after-free
> > and misc. kernel oops.
> >
> > Fixes: 59e139cf0b32 ("net: qmi_wwan: Add pass through mode")
> >
> > Signed-off-by: Kristian Evensen <kristian.evensen@gmail.com>
> > ---
> > drivers/net/usb/qmi_wwan.c | 4 ++++
> > 1 file changed, 4 insertions(+)
> >
> > diff --git a/drivers/net/usb/qmi_wwan.c b/drivers/net/usb/qmi_wwan.c
> > index db8d3a4f2678..5ac307eb0bfd 100644
> > --- a/drivers/net/usb/qmi_wwan.c
> > +++ b/drivers/net/usb/qmi_wwan.c
> > @@ -620,6 +620,10 @@ static int qmi_wwan_rx_fixup(struct usbnet *dev, struct sk_buff *skb)
> > return qmimux_rx_fixup(dev, skb);
> >
> > if (info->flags & QMI_WWAN_FLAG_PASS_THROUGH) {
> > + skb = skb_clone(skb, GFP_ATOMIC);
> > + if (!skb)
> > + return 0;
> > +
> > skb->protocol = htons(ETH_P_MAP);
> > return (netif_rx(skb) == NET_RX_SUCCESS);
> > }
>
> Thanks for pointing this out. But it still looks strange to me. Why do
> we call netif_rx(skb) here instead of just returning 1 and leave that
> for usbnet_skb_return()? With cloning we end up doing eth_type_trans()
> on the duplicate - is that wise?
Agreed on the cloning being a strange solution. Kristian, were you able
to reproduce the problem on upstream kernels?
It does look pretty strange that qmimux_rx_fixup() copies out all
packets and receives them, and then let's usbnet to process the
multi-frame skb without even fulling off the qmimux_hdr. I'm probably
missing something.. otherwise sth like FLAG_MULTI_PACKET may be in
order?
next prev parent reply other threads:[~2021-06-14 20:05 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-14 14:18 [PATCH net] qmi_wwan: Clone the skb when in pass-through mode Kristian Evensen
2021-06-14 14:45 ` Bjørn Mork
2021-06-14 15:49 ` Kristian Evensen
2021-06-14 17:02 ` Kristian Evensen
2021-06-14 20:05 ` Jakub Kicinski [this message]
2021-06-15 6:24 ` Bjørn Mork
2021-06-15 9:03 ` Kristian Evensen
2021-06-15 10:04 ` Bjørn Mork
2021-06-15 10:51 ` Kristian Evensen
2021-06-15 11:04 ` Kristian Evensen
2021-06-15 13:39 ` Bjørn Mork
2021-06-15 19:26 ` Jakub Kicinski
2021-06-15 19:27 ` Jakub Kicinski
2021-06-16 10:08 ` Kristian Evensen
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