linux-kernel - [PATCH 3.16 40/61] scsi: sg: fix static checker warning in sg_is_valid

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Date:   Tue, 09 Jun 2020 19:04:31 +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>,
        "Johannes Thumshirn" <jthumshirn@...e.de>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        "Dan Carpenter" <dan.carpenter@...cle.com>,
        "Colin Ian King" <colin.king@...onical.com>,
        "Greg Kroah-Hartman" <gregkh@...uxfoundation.org>,
        "Douglas Gilbert" <dgilbert@...erlog.com>
Subject: [PATCH 3.16 40/61] scsi: sg: fix static checker warning in
 sg_is_valid_dxfer

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

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

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

commit 14074aba4bcda3764c9a702b276308b89901d5b6 upstream.

dxfer_len is an unsigned int and we always assign a value > 0 to it, so
it doesn't make any sense to check if it is < 0. We can't really check
dxferp as well as we have both NULL and not NULL cases in the possible
call paths.

So just return true for SG_DXFER_FROM_DEV transfer in
sg_is_valid_dxfer().

Signed-off-by: Johannes Thumshirn <jthumshirn@...e.de>
Reported-by: Colin Ian King <colin.king@...onical.com>
Reported-by: Dan Carpenter <dan.carpenter@...cle.com>
Cc: Douglas Gilbert <dgilbert@...erlog.com>
Signed-off-by: Martin K. Petersen <martin.petersen@...cle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/scsi/sg.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

--- a/drivers/scsi/sg.c
+++ b/drivers/scsi/sg.c
@@ -796,8 +796,11 @@ static bool sg_is_valid_dxfer(sg_io_hdr_
 			return false;
 		return true;
 	case SG_DXFER_FROM_DEV:
-		if (hp->dxfer_len < 0)
-			return false;
+		/*
+		 * 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: