From: Paolo Abeni <pabeni@redhat.com>
To: Eric Dumazet <edumazet@google.com>
Cc: Eric Dumazet <eric.dumazet@gmail.com>,
"David S . Miller" <davem@davemloft.net>,
netdev <netdev@vger.kernel.org>
Subject: Re: [PATCH net] macsec: avoid use-after-free in macsec_handle_frame()
Date: Wed, 07 Oct 2020 16:45:51 +0200 [thread overview]
Message-ID: <e9c835401b45da48559f4f0c9347b60c2b9c0911.camel@redhat.com> (raw)
In-Reply-To: <CANn89iLcZit_0Og9MbW0x0bQ=-6pz18UpRN6RYOY12Czui1eMQ@mail.gmail.com>
On Wed, 2020-10-07 at 16:31 +0200, Eric Dumazet wrote:
> On Wed, Oct 7, 2020 at 4:09 PM Paolo Abeni <pabeni@redhat.com> wrote:
> > Hi,
> >
> > On Wed, 2020-10-07 at 01:42 -0700, Eric Dumazet wrote:
> > > @@ -1232,9 +1233,10 @@ static rx_handler_result_t macsec_handle_frame(struct sk_buff **pskb)
> > > macsec_rxsc_put(rx_sc);
> > >
> > > skb_orphan(skb);
> > > + len = skb->len;
> > > ret = gro_cells_receive(&macsec->gro_cells, skb);
> > > if (ret == NET_RX_SUCCESS)
> > > - count_rx(dev, skb->len);
> > > + count_rx(dev, len);
> > > else
> > > macsec->secy.netdev->stats.rx_dropped++;
> >
> > I'm sorry I'm low on coffee, but I can't see the race?!? here we are in
> > a BH section, and the above code dereference the skb only if it's has
> > been enqueued into the gro_cells napi. It could be dequeued/dropped
> > only after we leave this section ?!?
>
> We should think of this as an alias for napi_gro_receive(), and not
> make any assumptions.
> Semantically the skb has been given to another layer.
> netif_rx() can absolutely queue the skb to another cpu backlog (RPS,
> RFS...), and the other cpu might have consumed the skb right away.
Ah! I completely missed that code path in gro_cells_receive()!
Thank you for pointing that out!
Acked-by: Paolo Abeni <pabeni@redhat.com>
next prev parent reply other threads:[~2020-10-07 14:46 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-07 8:42 [PATCH net] macsec: avoid use-after-free in macsec_handle_frame() Eric Dumazet
2020-10-07 14:09 ` Paolo Abeni
2020-10-07 14:31 ` Eric Dumazet
2020-10-07 14:45 ` Paolo Abeni [this message]
2020-10-07 15:54 ` Eric Dumazet
2020-10-08 20:00 ` patchwork-bot+netdevbpf
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