[PATCH 4.9 61/88] s390/cio: cio_ignore_proc_seq_next should increase position index

Greg Kroah-Hartman
2020-03-10T12:46:32Z

From: Vasily Averin <vvs@virtuozzo.com>

[ 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>
---
drivers/s390/cio/blacklist.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/s390/cio/blacklist.c b/drivers/s390/cio/blacklist.c
index 9082476b51db9..4e9f794176d35 100644
--- a/drivers/s390/cio/blacklist.c
+++ b/drivers/s390/cio/blacklist.c
@@ -302,8 +302,10 @@ 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) {
@@ -313,7 +315,6 @@ cio_ignore_proc_seq_next(struct seq_file *s, void *it, loff_t *offset)
return NULL;
} else
iter->devno++;
- (*offset)++;
return iter;
}

--
2.20.1