staging: unisys: visorhba: fix s-Par to boot with option CONFIG_VMAP_STACK set to y

BugLink: http://bugs.launchpad.net/bugs/1764762

[ Upstream commit 3c2bf0bd ]

The root issue is that we are not allowed to have items on the
stack being passed to "DMA" like operations. In this case we have
a vmcall and an inline completion of scsi command.

This patch fixes the issue by moving the variables on stack in
do_scsi_nolinuxstat() to heap memory.
Signed-off-by: Sameer Wadgaonkar <sameer.wadgaonkar@unisys.com>
Signed-off-by: David Kershner <david.kershner@unisys.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Juerg Haefliger <juergh@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

drivers/staging/unisys/visorhba/visorhba_main.c

@@ -792,7 +792,7 @@ static void
 do_scsi_nolinuxstat(struct uiscmdrsp *cmdrsp, struct scsi_cmnd *scsicmd)
 {
 	struct scsi_device *scsidev;
-	unsigned char buf[36];
+	unsigned char *buf;
 	struct scatterlist *sg;
 	unsigned int i;
 	char *this_page;
@@ -807,6 +807,10 @@ do_scsi_nolinuxstat(struct uiscmdrsp *cmdrsp, struct scsi_cmnd *scsicmd)
 		if (cmdrsp->scsi.no_disk_result == 0)
 			return;
 
+		buf = kzalloc(sizeof(char) * 36, GFP_KERNEL);
+		if (!buf)
+			return;
+
 		/* Linux scsi code wants a device at Lun 0
 		 * to issue report luns, but we don't want
 		 * a disk there so we'll present a processor
@@ -820,6 +824,7 @@ do_scsi_nolinuxstat(struct uiscmdrsp *cmdrsp, struct scsi_cmnd *scsicmd)
 		if (scsi_sg_count(scsicmd) == 0) {
 			memcpy(scsi_sglist(scsicmd), buf,
 			       cmdrsp->scsi.bufflen);
+			kfree(buf);
 			return;
 		}
 
@@ -831,6 +836,7 @@ do_scsi_nolinuxstat(struct uiscmdrsp *cmdrsp, struct scsi_cmnd *scsicmd)
 			memcpy(this_page, buf + bufind, sg[i].length);
 			kunmap_atomic(this_page_orig);
 		}
+		kfree(buf);
 	} else {
 		devdata = (struct visorhba_devdata *)scsidev->host->hostdata;
 		for_each_vdisk_match(vdisk, devdata, scsidev) {