From: Andrew Melnichenko <andrew@daynix.com>
To: Jason Wang <jasowang@redhat.com>
Cc: mst@redhat.com, ast@kernel.org, daniel@iogearbox.net,
davem@davemloft.net, kuba@kernel.org, hawk@kernel.org,
john.fastabend@gmail.com, kvm@vger.kernel.org,
virtualization@lists.linux.dev, netdev@vger.kernel.org,
linux-kernel@vger.kernel.org, bpf@vger.kernel.org,
yuri.benditovich@daynix.com, yan@daynix.com
Subject: Re: [PATCH v2 1/1] vhost: Added pad cleanup if vnet_hdr is not present.
Date: Thu, 28 Mar 2024 09:46:36 +0200 [thread overview]
Message-ID: <CABcq3pFRookhQ8a8Sf9ri2ONOhHME9mXBMUZEOG1eGkJvAxQNw@mail.gmail.com> (raw)
In-Reply-To: <CACGkMEuW8jLvje0_oqCT=-ih9JEgxOrWRsvjvfwQXw=OWT_RtQ@mail.gmail.com>
Thanks, I'll look into it.
On Thu, Mar 28, 2024 at 6:03 AM Jason Wang <jasowang@redhat.com> wrote:
>
> On Thu, Mar 28, 2024 at 7:44 AM Andrew Melnychenko <andrew@daynix.com> wrote:
> >
> > When the Qemu launched with vhost but without tap vnet_hdr,
> > vhost tries to copy vnet_hdr from socket iter with size 0
> > to the page that may contain some trash.
> > That trash can be interpreted as unpredictable values for
> > vnet_hdr.
> > That leads to dropping some packets and in some cases to
> > stalling vhost routine when the vhost_net tries to process
> > packets and fails in a loop.
> >
> > Qemu options:
> > -netdev tap,vhost=on,vnet_hdr=off,...
> >
> > From security point of view, wrong values on field used later
> > tap's tap_get_user_xdp() and will affect skb gso and options.
> > Later the header(and data in headroom) should not be used by the stack.
> > Using custom socket as a backend to vhost_net can reveal some data
> > in the vnet_hdr, although it would require kernel access to implement.
> >
> > The issue happens because the value of sock_len in virtqueue is 0.
> > That value is set at vhost_net_set_features() with
> > VHOST_NET_F_VIRTIO_NET_HDR, also it's set to zero at device open()
> > and reset() routine.
> > So, currently, to trigger the issue, we need to set up qemu with
> > vhost=on,vnet_hdr=off, or do not configure vhost in the custom program.
> >
> > Signed-off-by: Andrew Melnychenko <andrew@daynix.com>
>
> Acked-by: Jason Wang <jasowang@redhat.com>
>
> It seems it has been merged by Michael.
>
> Thanks
>
> > ---
> > drivers/vhost/net.c | 3 +++
> > 1 file changed, 3 insertions(+)
> >
> > diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
> > index f2ed7167c848..57411ac2d08b 100644
> > --- a/drivers/vhost/net.c
> > +++ b/drivers/vhost/net.c
> > @@ -735,6 +735,9 @@ static int vhost_net_build_xdp(struct vhost_net_virtqueue *nvq,
> > hdr = buf;
> > gso = &hdr->gso;
> >
> > + if (!sock_hlen)
> > + memset(buf, 0, pad);
> > +
> > if ((gso->flags & VIRTIO_NET_HDR_F_NEEDS_CSUM) &&
> > vhost16_to_cpu(vq, gso->csum_start) +
> > vhost16_to_cpu(vq, gso->csum_offset) + 2 >
> > --
> > 2.43.0
> >
>
prev parent reply other threads:[~2024-03-28 8:12 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-27 23:18 [PATCH v2 1/1] vhost: Added pad cleanup if vnet_hdr is not present Andrew Melnychenko
2024-03-28 4:02 ` Jason Wang
2024-03-28 7:46 ` Andrew Melnichenko [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=CABcq3pFRookhQ8a8Sf9ri2ONOhHME9mXBMUZEOG1eGkJvAxQNw@mail.gmail.com \
--to=andrew@daynix.com \
--cc=ast@kernel.org \
--cc=bpf@vger.kernel.org \
--cc=daniel@iogearbox.net \
--cc=davem@davemloft.net \
--cc=hawk@kernel.org \
--cc=jasowang@redhat.com \
--cc=john.fastabend@gmail.com \
--cc=kuba@kernel.org \
--cc=kvm@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mst@redhat.com \
--cc=netdev@vger.kernel.org \
--cc=virtualization@lists.linux.dev \
--cc=yan@daynix.com \
--cc=yuri.benditovich@daynix.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).