From: Vasily Averin <vvs@virtuozzo.com>
Date: Fri, 24 Jan 2020 05:48:55 +0000 (+0300)
Subject: s390/cio: cio_ignore_proc_seq_next should increase position index
X-Git-Tag: v5.5.9~153
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=cd4129fd3aa5c300f25658b4bf37c293e4098eb3;p=users%2Fdwmw2%2Flinux.git

s390/cio: cio_ignore_proc_seq_next should increase position index

[ Upstream commit 8b101a5e14f2161869636ff9cb4907b7749dc0c2 ]

if seq_file .next fuction does not change position index,
read after some lseek can generate unexpected output.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=206283
Link: https://lore.kernel.org/r/d44c53a7-9bc1-15c7-6d4a-0c10cb9dffce@virtuozzo.com
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---

diff --git a/drivers/s390/cio/blacklist.c b/drivers/s390/cio/blacklist.c
index 2a3f874a21d54..9cebff8e8d740 100644
--- a/drivers/s390/cio/blacklist.c
+++ b/drivers/s390/cio/blacklist.c
@@ -303,8 +303,10 @@ static void *
 cio_ignore_proc_seq_next(struct seq_file *s, void *it, loff_t *offset)
 {
 	struct ccwdev_iter *iter;
+	loff_t p = *offset;
 
-	if (*offset >= (__MAX_SUBCHANNEL + 1) * (__MAX_SSID + 1))
+	(*offset)++;
+	if (p >= (__MAX_SUBCHANNEL + 1) * (__MAX_SSID + 1))
 		return NULL;
 	iter = it;
 	if (iter->devno == __MAX_SUBCHANNEL) {
@@ -314,7 +316,6 @@ cio_ignore_proc_seq_next(struct seq_file *s, void *it, loff_t *offset)
 			return NULL;
 	} else
 		iter->devno++;
-	(*offset)++;
 	return iter;
 }