linux-kernel - Re: [PATCH] IB/srpt: Fix passing zero to 'PTR

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Message-ID: <20201112183023.GB917484@nvidia.com>
Date:   Thu, 12 Nov 2020 14:30:23 -0400
From:   Jason Gunthorpe <jgg@...dia.com>
To:     Bart Van Assche <bvanassche@....org>
CC:     YueHaibing <yuehaibing@...wei.com>, <dledford@...hat.com>,
        <linux-rdma@...r.kernel.org>, <target-devel@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] IB/srpt: Fix passing zero to 'PTR_ERR'

On Thu, Nov 12, 2020 at 10:25:48AM -0800, Bart Van Assche wrote:
> On 11/12/20 9:20 AM, Jason Gunthorpe wrote:
> > I think it should be like this, Bart?
> > 
> > diff --git a/drivers/infiniband/ulp/srpt/ib_srpt.c b/drivers/infiniband/ulp/srpt/ib_srpt.c
> > index 6017d525084a0c..80f9673956ced2 100644
> > +++ b/drivers/infiniband/ulp/srpt/ib_srpt.c
> > @@ -2311,7 +2311,7 @@ static int srpt_cm_req_recv(struct srpt_device *const sdev,
> >   	mutex_lock(&sport->port_guid_id.mutex);
> >   	list_for_each_entry(stpg, &sport->port_guid_id.tpg_list, entry) {
> > -		if (!IS_ERR_OR_NULL(ch->sess))
> > +		if (ch->sess)
> >   			break;
> >   		ch->sess = target_setup_session(&stpg->tpg, tag_num,
> >   						tag_size, TARGET_PROT_NORMAL,
> > @@ -2321,12 +2321,12 @@ static int srpt_cm_req_recv(struct srpt_device *const sdev,
> >   	mutex_lock(&sport->port_gid_id.mutex);
> >   	list_for_each_entry(stpg, &sport->port_gid_id.tpg_list, entry) {
> > -		if (!IS_ERR_OR_NULL(ch->sess))
> > +		if (ch->sess)
> >   			break;
> >   		ch->sess = target_setup_session(&stpg->tpg, tag_num,
> >   					tag_size, TARGET_PROT_NORMAL, i_port_id,
> >   					ch, NULL);
> > -		if (!IS_ERR_OR_NULL(ch->sess))
> > +		if (ch->sess)
> >   			break;
> >   		/* Retry without leading "0x" */
> >   		ch->sess = target_setup_session(&stpg->tpg, tag_num,
> > @@ -2335,7 +2335,9 @@ static int srpt_cm_req_recv(struct srpt_device *const sdev,
> >   	}
> >   	mutex_unlock(&sport->port_gid_id.mutex);
> > -	if (IS_ERR_OR_NULL(ch->sess)) {
> > +	if (!ch->sess)
> > +		ch->sess = ERR_PTR(-ENOENT);
> > +	if (IS_ERR(ch->sess)) {
> >   		WARN_ON_ONCE(ch->sess == NULL);
> >   		ret = PTR_ERR(ch->sess);
> >   		ch->sess = NULL;
> > 
> 
> Hi Jason,
> 
> The ib_srpt driver accepts three different formats for the initiator ACL. Up
> to two of the three target_setup_session() calls will fail if the fifth
> argument of target_setup_session() does not use the format of the initiator
> ID in configfs. If the first or the second target_setup_session() call fails
> it is essential that later target_setup_session() calls happen. Hence the
> IS_ERR_OR_NULL(ch->sess) checks in the above loops.

IS_ERR_OR_NULL is an abomination, it should not be used.

I see I didn't quite get it right, but that is still closer to sane,
probably target_setup_session() should return NULL not err_ptr

Jason