From: "Serge E. Hallyn" <serge@hallyn.com>
To: "Paul E. McKenney" <paulmck@kernel.org>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>,
James Morris <jmorris@namei.org>,
linux-kernel@vger.kernel.org,
Madhuparna Bhowmik <madhuparnabhowmik10@gmail.com>,
linux-security-module@vger.kernel.org,
Joel Fernandes <joel@joelfernandes.org>,
linux-kernel-mentees@lists.linuxfoundation.org,
"Serge E . Hallyn" <serge@hallyn.com>
Subject: Re: [Linux-kernel-mentees] [PATCH RESEND] device_cgroup: Fix RCU list debugging warning
Date: Sun, 7 Jun 2020 23:17:34 -0500 [thread overview]
Message-ID: <20200608041734.GA10911@mail.hallyn.com> (raw)
In-Reply-To: <20200607190840.GG4455@paulmck-ThinkPad-P72>
On Sun, Jun 07, 2020 at 12:08:40PM -0700, Paul E. McKenney wrote:
> On Sun, Jun 07, 2020 at 06:23:40AM +1000, Stephen Rothwell wrote:
> > Hi all,
> >
> > On Mon, 6 Apr 2020 16:29:50 +0530 Amol Grover <frextrite@gmail.com> wrote:
> > >
> > > exceptions may be traversed using list_for_each_entry_rcu()
> > > outside of an RCU read side critical section BUT under the
> > > protection of decgroup_mutex. Hence add the corresponding
> > > lockdep expression to fix the following false-positive
> > > warning:
> > >
> > > [ 2.304417] =============================
> > > [ 2.304418] WARNING: suspicious RCU usage
> > > [ 2.304420] 5.5.4-stable #17 Tainted: G E
> > > [ 2.304422] -----------------------------
> > > [ 2.304424] security/device_cgroup.c:355 RCU-list traversed in non-reader section!!
> > >
> > > Signed-off-by: Amol Grover <frextrite@gmail.com>
> > > ---
> > > security/device_cgroup.c | 3 ++-
> > > 1 file changed, 2 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/security/device_cgroup.c b/security/device_cgroup.c
> > > index 7d0f8f7431ff..b7da9e0970d9 100644
> > > --- a/security/device_cgroup.c
> > > +++ b/security/device_cgroup.c
> > > @@ -352,7 +352,8 @@ static bool match_exception_partial(struct list_head *exceptions, short type,
> > > {
> > > struct dev_exception_item *ex;
> > >
> > > - list_for_each_entry_rcu(ex, exceptions, list) {
> > > + list_for_each_entry_rcu(ex, exceptions, list,
> > > + lockdep_is_held(&devcgroup_mutex)) {
> > > if ((type & DEVCG_DEV_BLOCK) && !(ex->type & DEVCG_DEV_BLOCK))
> > > continue;
> > > if ((type & DEVCG_DEV_CHAR) && !(ex->type & DEVCG_DEV_CHAR))
> > > --
> > > 2.24.1
> > >
> >
> > I have been carrying the above patch in linux-next for some time now.
> > I have been carrying it because it fixes problems for syzbot (see the
> > third warning in
> > https://lore.kernel.org/linux-next/CACT4Y+YnjK+kq0pfb5fe-q1bqe2T1jq_mvKHf--Z80Z3wkyK1Q@mail.gmail.com/).
> > Is there some reason it has not been applied to some tree?
>
> The RCU changes on which this patch depends have long since made it to
> mainline, so it can go up any tree. I can take it if no one else will,
> but it might be better going in via the security tree.
>
> Thanx, Paul
James, do you mind pulling it in?
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next prev parent reply other threads:[~2020-06-08 4:17 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-06 10:59 [Linux-kernel-mentees] [PATCH RESEND] device_cgroup: Fix RCU list debugging warning Amol Grover
2020-06-06 20:23 ` Stephen Rothwell
2020-06-07 19:08 ` Paul E. McKenney
2020-06-08 4:17 ` Serge E. Hallyn [this message]
2020-08-17 2:07 ` Stephen Rothwell
2020-08-20 18:28 ` James Morris
2020-08-20 22:38 ` Stephen Rothwell
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