linux-kernel - Re: [PATCH 1/2] scsi: Fix get_user() in call sg_scsi

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Date:   Thu, 17 Nov 2022 03:03:30 +0300
From:   "kirill@...temov.name" <kirill@...temov.name>
To:     David Laight <David.Laight@...LAB.COM>
Cc:     "'Kirill A. Shutemov'" <kirill.shutemov@...ux.intel.com>,
        "dave.hansen@...el.com" <dave.hansen@...el.com>,
        "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
        "jejb@...ux.ibm.com" <jejb@...ux.ibm.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "lkp@...el.com" <lkp@...el.com>,
        "martin.petersen@...cle.com" <martin.petersen@...cle.com>,
        "oe-kbuild-all@...ts.linux.dev" <oe-kbuild-all@...ts.linux.dev>,
        "x86@...nel.org" <x86@...nel.org>
Subject: Re: [PATCH 1/2] scsi: Fix get_user() in call sg_scsi_ioctl()

On Wed, Nov 16, 2022 at 10:40:09PM +0000, David Laight wrote:
> From: Kirill A. Shutemov
> > Sent: 16 November 2022 00:44
> > 
> > get_user() expects the pointer to be pointer-to-simple-variable type,
> > but sic->data is array of 'unsigned char'. It violates get_user()
> > contracts.
> > 
> > Cast it explicitly to 'unsigned char __user *'. It matches current
> > behaviour.
> > 
> > This is preparation for fixing sparse warnings caused by Linear Address
> > Masking patchset.
> > 
> > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> > Cc: "James E.J. Bottomley" <jejb@...ux.ibm.com>
> > Cc: "Martin K. Petersen" <martin.petersen@...cle.com>
> > ---
> >  drivers/scsi/scsi_ioctl.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/scsi/scsi_ioctl.c b/drivers/scsi/scsi_ioctl.c
> > index 2d20da55fb64..72b3ab5137b8 100644
> > --- a/drivers/scsi/scsi_ioctl.c
> > +++ b/drivers/scsi/scsi_ioctl.c
> > @@ -519,7 +519,7 @@ static int sg_scsi_ioctl(struct request_queue *q, fmode_t mode,
> >  		return -EFAULT;
> >  	if (in_len > PAGE_SIZE || out_len > PAGE_SIZE)
> >  		return -EINVAL;
> > -	if (get_user(opcode, sic->data))
> > +	if (get_user(opcode, (unsigned char __user *)sic->data))
> 
> Using &sic->data[0] should work and is much nicer than the cast.

Okay. Fair enough. Adjusted patch is below.

>From 86baed963c9295c067940479ab0f844c3644e1c9 Mon Sep 17 00:00:00 2001
From: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Date: Wed, 16 Nov 2022 03:22:28 +0300
Subject: [PATCHv2 1/2] scsi: Fix get_user() in call sg_scsi_ioctl()

get_user() expects the pointer to be pointer-to-simple-variable type,
but sic->data is array of 'unsigned char'. It violates get_user()
contracts.

Explicitly take pointer to the first element of the array. It matches
current behaviour.

This is preparation for fixing sparse warnings caused by Linear Address
Masking patchset.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
Cc: "James E.J. Bottomley" <jejb@...ux.ibm.com>
Cc: "Martin K. Petersen" <martin.petersen@...cle.com>
---
 drivers/scsi/scsi_ioctl.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/scsi/scsi_ioctl.c b/drivers/scsi/scsi_ioctl.c
index 2d20da55fb64..fdd47565a311 100644
--- a/drivers/scsi/scsi_ioctl.c
+++ b/drivers/scsi/scsi_ioctl.c
@@ -519,7 +519,7 @@ static int sg_scsi_ioctl(struct request_queue *q, fmode_t mode,
 		return -EFAULT;
 	if (in_len > PAGE_SIZE || out_len > PAGE_SIZE)
 		return -EINVAL;
-	if (get_user(opcode, sic->data))
+	if (get_user(opcode, &sic->data[0]))
 		return -EFAULT;
 
 	bytes = max(in_len, out_len);
-- 
  Kiryl Shutsemau / Kirill A. Shutemov