From: Peter Oberparleiter oberpar@linux.ibm.com
[ Upstream commit 1b6074112742f65ece71b0f299ca5a6a887d2db6 ]
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@vger.kernel.org # v5.15 Reported-by: Alexander Egorenkov egorenar@linux.ibm.com Reviewed-by: Vineeth Vijayan vneethv@linux.ibm.com Signed-off-by: Peter Oberparleiter oberpar@linux.ibm.com Signed-off-by: Vasily Gorbik gor@linux.ibm.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/s390/cio/css.c | 8 ++------ 1 file changed, 2 insertions(+), 6 deletions(-)
diff --git a/drivers/s390/cio/css.c b/drivers/s390/cio/css.c index ce9e7517430f..2ba9e0135565 100644 --- a/drivers/s390/cio/css.c +++ b/drivers/s390/cio/css.c @@ -792,13 +792,9 @@ static int __unset_online(struct device *dev, void *data) { 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; }