[SCSI] don't reference freed command in scsi_prep_return

Patch

commit 0479633686d370303e3430256ace4bd5f7f138dc
Author: Christoph Hellwig <hch@infradead.org>
Date:   Thu Feb 20 14:20:55 2014 -0800

    [SCSI] do not manipulate device reference counts in scsi_get/put_command

Introduced a use after free:I in the kill case of scsi_prep_return we have to
release our device reference, but we do this trying to reference the just
freed command.  Use the local sdev pointer instead.

Fixes: 0479633686d370303e3430256ace4bd5f7f138dc
Reported-by: Joe Lawrence <joe.lawrence@stratus.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 54eff6a79fb81e2bec5a2b7346af9b94d689e434..7fa54fe51f63fd8f684284f47207c499087bedb7 100644 (file)
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -1274,7 +1274,7 @@ int scsi_prep_return(struct request_queue *q, struct request *req, int ret)
                        struct scsi_cmnd *cmd = req->special;
                        scsi_release_buffers(cmd);
                        scsi_put_command(cmd);
-                       put_device(&cmd->device->sdev_gendev);
+                       put_device(&sdev->sdev_gendev);
                        req->special = NULL;
                }
                break;