Re: Early backport of Vhost regression fix in LTS branches

[Luca Boccassi <bluca@debian.org>]

On Tue, 20 Sept 2022 at 12:03, Kevin Traynor <ktraynor@redhat.com> wrote:
>
> On 20/09/2022 10:36, Maxime Coquelin wrote:
> > Hi LTS maintainers,
> >
> > We have discovered a regression causing deadlock in application using
> > the Vhost library (when vIOMMU is used & NUMA reallocation happens).
> >
> > The faulty commit [0] got backported in all maintained LTS branches,
> > following minor releases are impacted:
> > - V21.11.1+
> > - V20.11.5+
> > - V19.11.12+
> >
> > The fix for this regression is already in main branch, and will be part
> > of next v22.11 release.
> >
> > Discussing with Kevin, he suggested the fix to be backported early to
> > all the LTS branches.
> >
>
> This issue is a deadlock likely to occur with an application such as
> OVS, that uses vIOMMU vhost ports and a multi-NUMA system.
>
> In normal circumstances, for example with OVS, we could just recommend
> users not to upgrade to the latest DPDK LTS releases until the issue is
> fixed. Where this one gets tricky is that the latest LTS releases
> contains CVE fixes.
>
> At the moment if a user wants the CVE fixes *and* the below deadlock
> fix, they will have to pick patches themselves. It might help some if
> the DPDK stable branches (which are still at last release point)
> backport the fix below early so a user can just pull the branch.
>
> > Below is the fix to be backported:
> >
> > ======================================================================
> > commit 0b2a2ca35037d6a5168f0832c11d9858b8ae946a
> > Author: David Marchand <david.marchand@redhat.com>
> > Date:   Mon Jul 25 22:32:03 2022 +0200
> >
> >       vhost: fix virtqueue use after free on NUMA reallocation
> >
> >       translate_ring_addresses (via numa_realloc) may change a virtio
> > device and
> >       virtio queue.
> >       The virtqueue object must be refreshed before accessing the lock.
> >
> >       Fixes: 04c27cb673b9 ("vhost: fix unsafe vring addresses modifications")
> >       Cc: stable@dpdk.org
> >
> >       Signed-off-by: David Marchand <david.marchand@redhat.com>
> >       Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>
> > ======================================================================
> >
> > The fix can be backported without conflicts to all the LTS branches,
> > except for v19.11, for which the Vhost directory rename can cause
> > issues. It can be overcome using below command:
> >
> > git cherry-pick -Xfind-renames=5% 0b2a2ca350
> >
> > Is that OK for you?
> >
>
> I can take care of it for all branches if other maintainers are busy and
> ok with that.

Sounds good to me, feel free to go ahead for 20.11, thank you.

Kind regards,
Luca Boccassi