Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Message-ID: <095a2264120ad51d0500c4ce8221be2f88a9537e.camel@suse.com>
Subject: Re: [PATCH] scsi: Let scsi_execute_cmd() mark args->sshdr as invalid
From:   Martin Wilck <mwilck@suse.com>
To:     Juergen Gross <jgross@suse.com>, linux-kernel@vger.kernel.org,
        linux-scsi@vger.kernel.org
Cc:     "James E.J. Bottomley" <jejb@linux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@oracle.com>,
        stable@vger.kernel.org
Date:   Thu, 11 May 2023 15:10:47 +0200
In-Reply-To: <20230511123432.5793-1-jgross@suse.com>
References: <20230511123432.5793-1-jgross@suse.com>
Content-Type: text/plain; charset="ISO-8859-15"
Content-Transfer-Encoding: quoted-printable
User-Agent: Evolution 3.48.1 
MIME-Version: 1.0
Precedence: bulk

On Thu, 2023-05-11 at 14:34 +0200, Juergen Gross wrote:
> Some callers of scsi_execute_cmd() (like e.g. sd_spinup_disk()) are
> passing an uninitialized struct sshdr and don't look at the return
> value of scsi_execute_cmd() before looking at the contents of that
> struct.
>=20
> This can result in false positives when looking for specific error
> conditions.
>=20
> In order to fix that let scsi_execute_cmd() zero sshdr-
> >response_code,
> resulting in scsi_sense_valid() returning false.
>=20
> Cc: stable@vger.kernel.org
> Fixes: 3949e2f04262 ("scsi: simplify scsi_execute_req_flags")
> Signed-off-by: Juergen Gross <jgross@suse.com>
> ---
> I'm not aware of any real error having happened due to this problem,
> but I thought it should be fixed anyway.
> I _think_ 3949e2f04262 was introducing the problem, but I'm not 100%
> sure it is really the commit to be blamed.
> ---
> =A0drivers/scsi/scsi_lib.c | 14 ++++++++++----
> =A01 file changed, 10 insertions(+), 4 deletions(-)

One nitpick below, otherwise it looks good to me.

>=20
> diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
> index b7c569a42aa4..923336620bff 100644
> --- a/drivers/scsi/scsi_lib.c
> +++ b/drivers/scsi/scsi_lib.c
> @@ -209,11 +209,17 @@ int scsi_execute_cmd(struct scsi_device *sdev,
> const unsigned char *cmd,
> =A0=A0=A0=A0=A0=A0=A0=A0struct scsi_cmnd *scmd;
> =A0=A0=A0=A0=A0=A0=A0=A0int ret;
> =A0
> -=A0=A0=A0=A0=A0=A0=A0if (!args)
> +=A0=A0=A0=A0=A0=A0=A0if (!args) {
> =A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0args =3D &default_args;
> -=A0=A0=A0=A0=A0=A0=A0else if (WARN_ON_ONCE(args->sense &&
> -=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=
=A0=A0=A0=A0 args->sense_len !=3D
> SCSI_SENSE_BUFFERSIZE))
> -=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0return -EINVAL;
> +=A0=A0=A0=A0=A0=A0=A0} else {
> +=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0/* Mark sense data to be in=
valid. */
> +=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0if (args->sshdr)
> +=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0arg=
s->sshdr->response_code =3D 0;

We know for certain that sizeof(*sshdr) is 8 bytes, and will most
probably remain so. Thus=A0

    memset(sshdr, 0, sizeof(*sshdr))

would result in more efficient code.

Martin