linux-kernel - [PATCH 3.16 41/61] scsi: sg: only check for dxfer

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Date:   Tue, 09 Jun 2020 19:04:32 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, Denis Kirjanov <kda@...ux-powerpc.org>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        "" <stable@...r.kernel.org>,
        "Johannes Thumshirn" <jthumshirn@...e.de>,
        "Jason L Tibbitts III" <tibbs@...h.uh.edu>,
        "Hannes Reinecke" <hare@...e.com>,
        "Greg Kroah-Hartman" <gregkh@...uxfoundation.org>,
        "Doug Gilbert" <dgilbert@...erlog.com>
Subject: [PATCH 3.16 41/61] scsi: sg: only check for dxfer_len greater
 than 256M

3.16.85-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Johannes Thumshirn <jthumshirn@...e.de>

commit f930c7043663188429cd9b254e9d761edfc101ce upstream.

Don't make any assumptions on the sg_io_hdr_t::dxfer_direction or the
sg_io_hdr_t::dxferp in order to determine if it is a valid request. The
only way we can check for bad requests is by checking if the length
exceeds 256M.

Signed-off-by: Johannes Thumshirn <jthumshirn@...e.de>
Fixes: 28676d869bbb (scsi: sg: check for valid direction before starting the request)
Reported-by: Jason L Tibbitts III <tibbs@...h.uh.edu>
Tested-by: Jason L Tibbitts III <tibbs@...h.uh.edu>
Suggested-by: Doug Gilbert <dgilbert@...erlog.com>
Cc: Doug Gilbert <dgilbert@...erlog.com>
Cc: <stable@...r.kernel.org>
Reviewed-by: Hannes Reinecke <hare@...e.com>
Signed-off-by: Martin K. Petersen <martin.petersen@...cle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
[bwh: Backported to 3.16: Include <linux/sizes.h>]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/scsi/sg.c | 31 +------------------------------
 1 file changed, 1 insertion(+), 30 deletions(-)

--- a/drivers/scsi/sg.c
+++ b/drivers/scsi/sg.c
@@ -54,6 +54,7 @@ static int sg_version_num = 30534;	/* 2
 #include <linux/atomic.h>
 #include <linux/ratelimit.h>
 #include <linux/cred.h> /* for sg_check_file_access() */
+#include <linux/sizes.h>
 
 #include "scsi.h"
 #include <scsi/scsi_dbg.h>
@@ -788,35 +789,6 @@ sg_new_write(Sg_fd *sfp, struct file *fi
 	return count;
 }
 
-static bool sg_is_valid_dxfer(sg_io_hdr_t *hp)
-{
-	switch (hp->dxfer_direction) {
-	case SG_DXFER_NONE:
-		if (hp->dxferp || hp->dxfer_len > 0)
-			return false;
-		return true;
-	case SG_DXFER_FROM_DEV:
-		/*
-		 * for SG_DXFER_FROM_DEV we always set dxfer_len to > 0. dxferp
-		 * can either be NULL or != NULL so there's no point in checking
-		 * it either. So just return true.
-		 */
-		return true;
-	case SG_DXFER_TO_DEV:
-	case SG_DXFER_TO_FROM_DEV:
-		if (!hp->dxferp || hp->dxfer_len == 0)
-			return false;
-		return true;
-	case SG_DXFER_UNKNOWN:
-		if ((!hp->dxferp && hp->dxfer_len) ||
-		    (hp->dxferp && hp->dxfer_len == 0))
-			return false;
-		return true;
-	default:
-		return false;
-	}
-}
-
 static int
 sg_common_write(Sg_fd * sfp, Sg_request * srp,
 		unsigned char *cmnd, int timeout, int blocking)
@@ -836,7 +808,7 @@ sg_common_write(Sg_fd * sfp, Sg_request
 	SCSI_LOG_TIMEOUT(4, printk("sg_common_write:  scsi opcode=0x%02x, cmd_size=%d\n",
 			  (int) cmnd[0], (int) hp->cmd_len));
 
-	if (!sg_is_valid_dxfer(hp))
+	if (hp->dxfer_len >= SZ_256M)
 		return -EINVAL;
 
 	k = sg_start_req(srp, cmnd);