linux-kernel - Re: qib_lookup_qpn() appears to leak pointer out of rcu_read

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Message-ID: <20140212145543.GY4250@linux.vnet.ibm.com>
Date:	Wed, 12 Feb 2014 06:55:43 -0800
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	"Marciniszyn, Mike" <mike.marciniszyn@...el.com>
Cc:	"roland@...nel.org" <roland@...nel.org>,
	"Hefty, Sean" <sean.hefty@...el.com>,
	"hal.rosenstock@...il.com" <hal.rosenstock@...il.com>,
	"linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: qib_lookup_qpn() appears to leak pointer out of rcu_read_unlock()

On Wed, Feb 12, 2014 at 01:59:30PM +0000, Marciniszyn, Mike wrote:
> > So what am I missing here?
> > 
> 
> The atomic increment of a reference count:

Got it, thank you, apologies for the noise!

							Thanx, Paul

> struct qib_qp *qib_lookup_qpn(struct qib_ibport *ibp, u32 qpn)
> {
>         struct qib_qp *qp = NULL;
> 
>         rcu_read_lock();
>         if (unlikely(qpn <= 1)) {
>                 if (qpn == 0)
>                         qp = rcu_dereference(ibp->qp0);
>                 else
>                         qp = rcu_dereference(ibp->qp1);
>                 if (qp)
>                         atomic_inc(&qp->refcount); <--------------------------
>         } else {
>                 struct qib_ibdev *dev = &ppd_from_ibp(ibp)->dd->verbs_dev;
>                 unsigned n = qpn_hash(dev, qpn);
> 
>                 for (qp = rcu_dereference(dev->qp_table[n]); qp;
>                         qp = rcu_dereference(qp->next))
>                         if (qp->ibqp.qp_num == qpn) {
>                                 atomic_inc(&qp->refcount); <---------------------
>                                 break;
>                         }
>         }
>         rcu_read_unlock();
>         return qp;
> }
> 
> Mike
> 

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