linux-kernel - Re: [PATCH v3] kernel: audit.c: Add _

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Message-ID: <20191202233431.GM17234@google.com>
Date:   Mon, 2 Dec 2019 18:34:31 -0500
From:   Joel Fernandes <joel@...lfernandes.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Amol Grover <frextrite@...il.com>,
        Paul Moore <paul@...l-moore.com>,
        Eric Paris <eparis@...hat.com>, linux-audit@...hat.com,
        linux-kernel@...r.kernel.org,
        linux-kernel-mentees@...ts.linuxfoundation.org,
        Shuah Khan <skhan@...uxfoundation.org>, paulmck@...nel.org,
        rcu@...r.kernel.org, rostedt@...nel.org
Subject: Re: [PATCH v3] kernel: audit.c: Add __rcu annotation to RCU pointer

On Mon, Dec 02, 2019 at 05:26:39PM -0500, Steven Rostedt wrote:
> On Mon, 2 Dec 2019 16:19:15 -0500
> Joel Fernandes <joel@...lfernandes.org> wrote:
> 
> > Good idea to CC the following on RCU patches:
> > Paul McKenney
> > Steven Rostedt
> 
> I'm fine with this if it doesn't cause any rcu splats with sparse. Not
> sure if use cases of RCU requires RCU maintainers Cc'd. Although we can
> usually keep people from misusing it ;-)

Yes true :) Thanks for taking a look.

 - Joel

> 
> -- Steve
> 
> 
> > (Any others on the RCU maintainers list).
> > And, the list: rcu@...r.kernel.org
> > 
> > Could anyone Ack the patch? Looks safe and straight forward.
> > 
> > On Mon, Dec 02, 2019 at 12:03:48AM +0530, Amol Grover wrote:
> > > Add __rcu annotation to RCU-protected global pointer auditd_conn.
> > > 
> > > auditd_conn is an RCU-protected global pointer,i.e., accessed
> > > via RCU methods rcu_dereference() and rcu_assign_pointer(),
> > > hence it must be annotated with __rcu for sparse to report
> > > warnings/errors correctly.
> > > 
> > > Fix multiple instances of the sparse error:
> > > error: incompatible types in comparison expression
> > > (different address spaces)
> > > 
> > > Reviewed-by: Joel Fernandes (Google) <joel@...lfernandes.org>
> > > Signed-off-by: Amol Grover <frextrite@...il.com>
> > > ---
> > > v3:
> > > - update changelog to be more descriptive
> > > 
> > > v2:
> > > - fix erroneous RCU pointer initialization
> > >  
> > >  kernel/audit.c | 5 +++--
> > >  1 file changed, 3 insertions(+), 2 deletions(-)
> > > 
> > > diff --git a/kernel/audit.c b/kernel/audit.c
> > > index da8dc0db5bd3..ff7cfc61f53d 100644
> > > --- a/kernel/audit.c
> > > +++ b/kernel/audit.c
> > > @@ -102,12 +102,13 @@ struct audit_net {
> > >   * This struct is RCU protected; you must either hold the RCU lock for reading
> > >   * or the associated spinlock for writing.
> > >   */
> > > -static struct auditd_connection {
> > > +struct auditd_connection {
> > >  	struct pid *pid;
> > >  	u32 portid;
> > >  	struct net *net;
> > >  	struct rcu_head rcu;
> > > -} *auditd_conn = NULL;
> > > +};
> > > +static struct auditd_connection __rcu *auditd_conn;
> > >  static DEFINE_SPINLOCK(auditd_conn_lock);
> > >  
> > >  /* If audit_rate_limit is non-zero, limit the rate of sending audit records
> > > -- 
> > > 2.24.0
> > >   
>