[bionic][PATCH 2/2] srcu: Lock srcu_data structure in srcu_gp_start()

Joshua R. Poulson jrp at pun.org
Thu Feb 28 01:00:39 UTC 2019


I did submit this one in
https://bugs.launchpad.net/ubuntu/+source/linux-azure/+bug/1802021 for
an Azure customer that was having an issue. This patch addressed their
problem, but later in that same bug was another user who was
experiencing issues that was looking for the same fix in the generic
kernels.

Thanks, --jrp

On Wed, Feb 27, 2019 at 3:22 PM Marcelo Henrique Cerri
<marcelo.cerri at canonical.com> wrote:
>
> My mistake. I used the patches that went into linux-azure to prepare it.
>
> I will update it and re-submit it first thing in the morning.
>
> On Wed, Feb 27, 2019 at 10:38:23AM +0100, Stefan Bader wrote:
> > On 21.02.19 00:28, Marcelo Henrique Cerri wrote:
> > > From: Dennis Krein <Dennis.Krein at netapp.com>
> > >
> > > BugLink: http://bugs.launchpad.net/bugs/1802021
> > >
> > > The srcu_gp_start() function is called with the srcu_struct structure's
> > > ->lock held, but not with the srcu_data structure's ->lock.  This is
> > > problematic because this function accesses and updates the srcu_data
> > > structure's ->srcu_cblist, which is protected by that lock.  Failing to
> > > hold this lock can result in corruption of the SRCU callback lists,
> > > which in turn can result in arbitrarily bad results.
> > >
> > > This commit therefore makes srcu_gp_start() acquire the srcu_data
> > > structure's ->lock across the calls to rcu_segcblist_advance() and
> > > rcu_segcblist_accelerate(), thus preventing this corruption.
> > >
> > > Reported-by: Bart Van Assche <bvanassche at acm.org>
> > > Reported-by: Christoph Hellwig <hch at infradead.org>
> > > Reported-by: Sebastian Kuzminsky <seb.kuzminsky at gmail.com>
> > > Signed-off-by: Dennis Krein <Dennis.Krein at netapp.com>
> > > Signed-off-by: Paul E. McKenney <paulmck at linux.ibm.com>
> > > Tested-by: Dennis Krein <Dennis.Krein at netapp.com>
> > > Cc: <stable at vger.kernel.org> # 4.16.x
> > > (cherry picked from commit eb4c2382272ae7ae5d81fdfa5b7a6c86146eaaa4)
> > > Acked-by: Stefan Bader <stefan.bader at canonical.com>
> > > Acked-by: Kleber Sacilotto de Souza <kleber.souza at canonical.com>
> > > Signed-off-by: Marcelo Henrique Cerri <marcelo.cerri at canonical.com>
> > > ---
> >
> > Cannot remember having acked this yet...
> >
> > >  kernel/rcu/srcutree.c | 2 ++
> > >  1 file changed, 2 insertions(+)
> > >
> > > diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c
> > > index d5cea81378cc..b3e5e9873582 100644
> > > --- a/kernel/rcu/srcutree.c
> > > +++ b/kernel/rcu/srcutree.c
> > > @@ -441,10 +441,12 @@ static void srcu_gp_start(struct srcu_struct *sp)
> > >
> > >     lockdep_assert_held(&sp->lock);
> > >     WARN_ON_ONCE(ULONG_CMP_GE(sp->srcu_gp_seq, sp->srcu_gp_seq_needed));
> > > +   spin_lock_rcu_node(sdp);  /* Interrupts already disabled. */
> > >     rcu_segcblist_advance(&sdp->srcu_cblist,
> > >                           rcu_seq_current(&sp->srcu_gp_seq));
> > >     (void)rcu_segcblist_accelerate(&sdp->srcu_cblist,
> > >                                    rcu_seq_snap(&sp->srcu_gp_seq));
> > > +   spin_unlock_rcu_node(sdp);  /* Interrupts remain disabled. */
> > >     smp_mb(); /* Order prior store to ->srcu_gp_seq_needed vs. GP start. */
> > >     rcu_seq_start(&sp->srcu_gp_seq);
> > >     state = rcu_seq_state(READ_ONCE(sp->srcu_gp_seq));
> > >
> >
> >
>
>
>
>
> --
> Regards,
> Marcelo
>
> --
> kernel-team mailing list
> kernel-team at lists.ubuntu.com
> https://lists.ubuntu.com/mailman/listinfo/kernel-team



More information about the kernel-team mailing list