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From:   Oleksandr Natalenko <oleksandr@redhat.com>
To:     "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Cc:     David Laight <David.Laight@aculab.com>,
        "linux-scsi@vger.kernel.org" <linux-scsi@vger.kernel.org>,
        Saurav Kashyap <skashyap@marvell.com>,
        Johannes Thumshirn <Johannes.Thumshirn@wdc.com>,
        "GR-QLogic-Storage-Upstream@marvell.com" 
        <GR-QLogic-Storage-Upstream@marvell.com>,
        "James E.J. Bottomley" <jejb@linux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@oracle.com>,
        Jozef Bacik <jobacik@redhat.com>,
        Laurence Oberman <loberman@redhat.com>,
        Rob Evers <revers@redhat.com>
Subject: Re: [PATCH 1/3] scsi: qedf: do not touch __user pointer in
 qedf_dbg_stop_io_on_error_cmd_read() directly
Date:   Mon, 31 Jul 2023 10:01:46 +0200
Message-ID: <2690368.mvXUDI8C0e@redhat.com>
Organization: Red Hat
In-Reply-To: <314512939ebd44508b767d799e7c30af@AcuMS.aculab.com>
References: <20230728065819.139694-1-oleksandr@redhat.com>
 <20230728065819.139694-2-oleksandr@redhat.com>
 <314512939ebd44508b767d799e7c30af@AcuMS.aculab.com>
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From: Oleksandr Natalenko <oleksandr@redhat.com>
To: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Date: Mon, 31 Jul 2023 10:01:46 +0200
Message-ID: <2690368.mvXUDI8C0e@redhat.com>
Organization: Red Hat
In-Reply-To: <314512939ebd44508b767d799e7c30af@AcuMS.aculab.com>
MIME-Version: 1.0

Hello.

On p=C3=A1tek 28. =C4=8Dervence 2023 17:23:25 CEST David Laight wrote:
> From: Oleksandr Natalenko
> > Sent: 28 July 2023 07:58
> >=20
> > The qedf_dbg_stop_io_on_error_cmd_read() function invokes sprintf()
> > directly on a __user pointer, which may crash the kernel.
> >=20
> > Avoid doing that by using a small on-stack buffer for sprintf()
> > and then calling simple_read_from_buffer() which does a proper
> > copy_to_user() call.
> >=20
> > Fixes: 61d8658b4a ("scsi: qedf: Add QLogic FastLinQ offload FCoE driver=
 framework.")
> ...
> > diff --git a/drivers/scsi/qedf/qedf_debugfs.c b/drivers/scsi/qedf/qedf_=
debugfs.c
> > index a3ed681c8ce3f..4d1b99569d490 100644
> > --- a/drivers/scsi/qedf/qedf_debugfs.c
> > +++ b/drivers/scsi/qedf/qedf_debugfs.c
> > @@ -185,18 +185,17 @@ qedf_dbg_stop_io_on_error_cmd_read(struct file *f=
ilp, char __user *buffer,
> >  				   size_t count, loff_t *ppos)
> >  {
> >  	int cnt;
> > +	char cbuf[7];
> >  	struct qedf_dbg_ctx *qedf_dbg =3D
> >  				(struct qedf_dbg_ctx *)filp->private_data;
> >  	struct qedf_ctx *qedf =3D container_of(qedf_dbg,
> >  	    struct qedf_ctx, dbg_ctx);
> >=20
> >  	QEDF_INFO(qedf_dbg, QEDF_LOG_DEBUGFS, "entered\n");
> > -	cnt =3D sprintf(buffer, "%s\n",
> > +	cnt =3D sprintf(cbuf, "%s\n",
> >  	    qedf->stop_io_on_error ? "true" : "false");
>=20
> You've made cbuf[] exactly just big enough.
> If anyone breathes on this code it could overflow.
> You really should use scnprintf() for safety.

OK, I'll do scnprintf(cbuf, sizeof(cbuf), ...) in the next version of the s=
ubmission.

Thanks.

> >=20
> > -	cnt =3D min_t(int, count, cnt - *ppos);
> > -	*ppos +=3D cnt;
> > -	return cnt;
> > +	return simple_read_from_buffer(buffer, count, ppos, cbuf, cnt);
>=20
> Or just:
> 	if (gedf->stop_on_error)
> 		return simple_read_from_buffer(buffer, count, ppos, "true\n", 5);
> 	return simple_read_from_buffer(buffer, count, ppos, "false\n", 6);
>=20
> 	David
>=20
> =09
> >  }
> >=20
> >  static ssize_t
> > --
> > 2.41.0
>=20
> -
> Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1=
 1PT, UK
> Registration No: 1397386 (Wales)
>=20
>=20


=2D-=20
Oleksandr Natalenko (post-factum)
Principal Software Maintenance Engineer
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