Re: [PATCH] scsi: xen-scsifront: add error handling for xenbus_printf

From: Zhouyang Jia <jiazhouyang09@gmail.com>
To: Finn Thain <fthain@telegraphics.com.au>
Cc: Juergen Gross <jgross@suse.com>,
	"James E.J. Bottomley" <jejb@linux.vnet.ibm.com>,
	"Martin K. Petersen" <martin.petersen@oracle.com>,
	linux-scsi@vger.kernel.org,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	xen-devel@lists.xenproject.org,
	Boris Ostrovsky <boris.ostrovsky@oracle.com>
Subject: Re: [PATCH] scsi: xen-scsifront: add error handling for xenbus_printf
Date: Thu, 14 Jun 2018 16:13:21 +0800	[thread overview]
Message-ID: <CABb2TxJCd9Q0KUeeqZ_CZ-HwmkAVoktDLxq0TrThM2rFe4jePQ@mail.gmail.com> (raw)
In-Reply-To: <alpine.LNX.2.21.1806132002180.45@nippy.intranet>

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Hi,

Sorry for the mistakes, I'll fix this in v2.

Best,
Zhouyang

2018-06-13 18:09 GMT+08:00 Finn Thain <fthain@telegraphics.com.au>:

> On Tue, 12 Jun 2018, Zhouyang Jia wrote:
>
> > When xenbus_printf fails, the lack of error-handling code may
> > cause unexpected results.
> >
> > This patch adds error-handling code after calling xenbus_printf.
> >
> > Signed-off-by: Zhouyang Jia <jiazhouyang09@gmail.com>
> > ---
> >  drivers/scsi/xen-scsifront.c | 31 ++++++++++++++++++++++++-------
> >  1 file changed, 24 insertions(+), 7 deletions(-)
> >
> > diff --git a/drivers/scsi/xen-scsifront.c b/drivers/scsi/xen-scsifront.c
> > index 36f59a1..3d858ac 100644
> > --- a/drivers/scsi/xen-scsifront.c
> > +++ b/drivers/scsi/xen-scsifront.c
> > @@ -654,10 +654,17 @@ static int scsifront_dev_reset_handler(struct
> scsi_cmnd *sc)
> >  static int scsifront_sdev_configure(struct scsi_device *sdev)
> >  {
> >       struct vscsifrnt_info *info = shost_priv(sdev->host);
> > +     struct xenbus_device *dev = info->dev;
> > +     int err;
> >
> > -     if (info && current == info->curr)
> > -             xenbus_printf(XBT_NIL, info->dev->nodename,
> > +     if (info && current == info->curr) {
> > +             err = xenbus_printf(XBT_NIL, info->dev->nodename,
> >                             info->dev_state_path, "%d",
> XenbusStateConnected);
>
> The existing code checks whether 'info' is NULL before dereferencing it.
> But your patch checks for NULL after dereferencing.
>
> > +             if (err) {
> > +                     dev_err(&dev->dev, "writing dev_state_path\n");
> > +                     return err;
> > +             }
> > +     }
> >
> >       return 0;
> >  }
> > @@ -665,10 +672,15 @@ static int scsifront_sdev_configure(struct
> scsi_device *sdev)
> >  static void scsifront_sdev_destroy(struct scsi_device *sdev)
> >  {
> >       struct vscsifrnt_info *info = shost_priv(sdev->host);
> > +     struct xenbus_device *dev = info->dev;
> > +     int err;
> >
> > -     if (info && current == info->curr)
> > -             xenbus_printf(XBT_NIL, info->dev->nodename,
> > +     if (info && current == info->curr) {
> > +             err = xenbus_printf(XBT_NIL, info->dev->nodename,
> >                             info->dev_state_path, "%d",
> XenbusStateClosed);
>
> Same here.
>
> > +             if (err)
> > +                     dev_err(&dev->dev, "writing dev_state_path\n");
> > +     }
> >  }
> >
> >  static struct scsi_host_template scsifront_sht = {
>
> --
>

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