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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org,
        Sameer Wadgaonkar <sameer.wadgaonkar@unisys.com>,
        David Kershner <david.kershner@unisys.com>,
        Sasha Levin <alexander.levin@microsoft.com>
Subject: [PATCH 4.9 088/177] staging: unisys: visorhba: fix s-Par to boot with option CONFIG_VMAP_STACK set to y
Date:   Fri, 23 Mar 2018 10:53:36 +0100
Message-Id: <20180323094209.170789235@linuxfoundation.org>
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4.9-stable review patch.  If anyone has any objections, please let me know.

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

From: Sameer Wadgaonkar <sameer.wadgaonkar@unisys.com>


[ Upstream commit 3c2bf0bd08123f3497bd3e84bd9088c937b0cb40 ]

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>
---
 drivers/staging/unisys/visorhba/visorhba_main.c |    8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

--- a/drivers/staging/unisys/visorhba/visorhba_main.c
+++ b/drivers/staging/unisys/visorhba/visorhba_main.c
@@ -842,7 +842,7 @@ 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;
@@ -857,6 +857,10 @@ do_scsi_nolinuxstat(struct uiscmdrsp *cm
 		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
@@ -868,6 +872,7 @@ do_scsi_nolinuxstat(struct uiscmdrsp *cm
 		if (scsi_sg_count(scsicmd) == 0) {
 			memcpy(scsi_sglist(scsicmd), buf,
 			       cmdrsp->scsi.bufflen);
+			kfree(buf);
 			return;
 		}
 
@@ -879,6 +884,7 @@ do_scsi_nolinuxstat(struct uiscmdrsp *cm
 			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) {