From: Peter Oberparleiter <oberpar@xxxxxxxxxxxxx>
commit 1b6074112742f65ece71b0f299ca5a6a887d2db6 upstream.
The channel-subsystem-driver scans for newly available devices whenever
device-IDs are removed from the cio_ignore list using a command such as:
echo free >/proc/cio_ignore
Since an I/O device scan might interfer with running I/Os, commit
172da89ed0ea ("s390/cio: avoid excessive path-verification requests")
introduced an optimization to exclude online devices from the scan.
The newly added check for online devices incorrectly assumes that
an I/O-subchannel's drvdata points to a struct io_subchannel_private.
For devices that are bound to a non-default I/O subchannel driver, such
as the vfio_ccw driver, this results in an out-of-bounds read access
during each scan.
Fix this by changing the scan logic to rely on a driver-independent
online indication. For this we can use struct subchannel->config.ena,
which is the driver's requested subchannel-enabled state. Since I/Os
can only be started on enabled subchannels, this matches the intent
of the original optimization of not scanning devices where I/O might
be running.
Fixes: 172da89ed0ea ("s390/cio: avoid excessive path-verification requests")
Fixes: 0c3812c347bf ("s390/cio: derive cdev information only for IO-subchannels")
Cc: <stable@xxxxxxxxxxxxxxx> # v5.15
Reported-by: Alexander Egorenkov <egorenar@xxxxxxxxxxxxx>
Reviewed-by: Vineeth Vijayan <vneethv@xxxxxxxxxxxxx>
Signed-off-by: Peter Oberparleiter <oberpar@xxxxxxxxxxxxx>
Signed-off-by: Vasily Gorbik <gor@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/s390/cio/css.c | 8 ++------
1 file changed, 2 insertions(+), 6 deletions(-)
--- a/drivers/s390/cio/css.c
+++ b/drivers/s390/cio/css.c
@@ -753,13 +753,9 @@ static int __unset_online(struct device
{
struct idset *set = data;
struct subchannel *sch = to_subchannel(dev);
- struct ccw_device *cdev;
- if (sch->st == SUBCHANNEL_TYPE_IO) {
- cdev = sch_get_cdev(sch);
- if (cdev && cdev->online)
- idset_sch_del(set, sch->schid);
- }
+ if (sch->st == SUBCHANNEL_TYPE_IO && sch->config.ena)
+ idset_sch_del(set, sch->schid);
return 0;
}
