BugLink: https://bugs.launchpad.net/bugs/1868628

[ Upstream commit 8b101a5e ]

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.comReviewed-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>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>
Signed-off-by: Kelsey Skunberg <kelsey.skunberg@canonical.com>