linux-kernel - [PATCH 79/91] SCSI: scsi_lib: fix potential NULL dereference

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Message-Id: <20120205220952.826423599@pcw.home.local>
Date:	Sun, 05 Feb 2012 23:11:08 +0100
From:	Willy Tarreau <w@....eu>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	Jiri Slaby <jirislaby@...il.com>,
	James Bottomley <James.Bottomley@...e.de>,
	Greg KH <gregkh@...uxfoundation.org>
Subject: [PATCH 79/91] SCSI: scsi_lib: fix potential NULL dereference

2.6.27-longterm review patch.  If anyone has any objections, please let us know.

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

commit 03b147083a2f9a2a3fbbd2505fa88ffa3c6ab194 upstream.

Stanse found a potential NULL dereference in scsi_kill_request.

Instead of triggering BUG() in 'if (unlikely(cmd == NULL))' branch,
the kernel will Oops earlier on cmd dereference.

Move the dereferences after the if.

[ WT: starget is not set in 2.6.27 ]

Signed-off-by: Jiri Slaby <jirislaby@...il.com>
Signed-off-by: James Bottomley <James.Bottomley@...e.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>
---
 drivers/scsi/scsi_lib.c |    9 ++++++---
 1 files changed, 6 insertions(+), 3 deletions(-)

Index: longterm-2.6.27/drivers/scsi/scsi_lib.c
===================================================================
--- longterm-2.6.27.orig/drivers/scsi/scsi_lib.c	2012-02-05 22:34:42.697916475 +0100
+++ longterm-2.6.27/drivers/scsi/scsi_lib.c	2012-02-05 22:34:46.142917247 +0100
@@ -1389,8 +1389,8 @@
 static void scsi_kill_request(struct request *req, struct request_queue *q)
 {
 	struct scsi_cmnd *cmd = req->special;
-	struct scsi_device *sdev = cmd->device;
-	struct Scsi_Host *shost = sdev->host;
+	struct scsi_device *sdev;
+	struct Scsi_Host *shost;
 
 	blkdev_dequeue_request(req);
 
@@ -1400,6 +1400,8 @@
 		BUG();
 	}
 
+	sdev = cmd->device;
+	shost = sdev->host;
 	scsi_init_cmd_errh(cmd);
 	cmd->result = DID_NO_CONNECT << 16;
 	atomic_inc(&cmd->device->iorequest_cnt);


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