From efa70f3da72a34b691a78332a325d24529fdd10b Mon Sep 17 00:00:00 2001
From: Vineeth Vijayan <vneethv@linux.ibm.com>
Date: Fri, 5 Nov 2021 16:44:51 +0100
Subject: [PATCH] s390/cio: check the subchannel validity for dev_busid
Git-commit: a4751f157c194431fae9e9c493f456df8272b871
Patch-mainline: v5.16-rc1
References: stable-5.14.19

commit a4751f157c194431fae9e9c493f456df8272b871 upstream.

Check the validity of subchanel before reading other fields in
the schib.

Fixes: d3683c055212 ("s390/cio: add dev_busid sysfs entry for each subchannel")
Cc: <stable@vger.kernel.org>
Reported-by: Cornelia Huck <cohuck@redhat.com>
Signed-off-by: Vineeth Vijayan <vneethv@linux.ibm.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Link: https://lore.kernel.org/r/20211105154451.847288-1-vneethv@linux.ibm.com
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/s390/cio/css.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/s390/cio/css.c b/drivers/s390/cio/css.c
index 9fcdb8d81eee..3b912ef43170 100644
--- a/drivers/s390/cio/css.c
+++ b/drivers/s390/cio/css.c
@@ -437,8 +437,8 @@ static ssize_t dev_busid_show(struct device *dev,
 	struct subchannel *sch = to_subchannel(dev);
 	struct pmcw *pmcw = &sch->schib.pmcw;
 
-	if ((pmcw->st == SUBCHANNEL_TYPE_IO ||
-	     pmcw->st == SUBCHANNEL_TYPE_MSG) && pmcw->dnv)
+	if ((pmcw->st == SUBCHANNEL_TYPE_IO && pmcw->dnv) ||
+	    (pmcw->st == SUBCHANNEL_TYPE_MSG && pmcw->w))
 		return sysfs_emit(buf, "0.%x.%04x\n", sch->schid.ssid,
 				  pmcw->dev);
 	else
-- 
2.26.2