From: Jan Höppner <hoeppner@xxxxxxxxxxxxx>
In dasd_profile_start() the amount of requests on the device queue are
counted. The access to the device queue is unprotected against
concurrent access. With a lot of parallel I/O, especially with alias
devices enabled, the device queue can change while dasd_profile_start()
is accessing the queue. In the worst case this leads to a kernel panic
due to incorrect pointer accesses.
Fix this by taking the device lock before accessing the queue and
counting the requests. Additionally the check for a valid profile data
pointer can be done earlier to avoid unnecessary locking in a hot path.
Cc: stable@xxxxxxxxxxxxxxx
Fixes: 4fa52aa7a82f ("[S390] dasd: add enhanced DASD statistics interface")
Reviewed-by: Stefan Haberland <sth@xxxxxxxxxxxxx>
Signed-off-by: Jan Höppner <hoeppner@xxxxxxxxxxxxx>
Signed-off-by: Stefan Haberland <sth@xxxxxxxxxxxxx>
---
drivers/s390/block/dasd.c | 24 +++++++++++++-----------
1 file changed, 13 insertions(+), 11 deletions(-)
diff --git a/drivers/s390/block/dasd.c b/drivers/s390/block/dasd.c
index 215597f73be4..5b11ee923457 100644
--- a/drivers/s390/block/dasd.c
+++ b/drivers/s390/block/dasd.c
@@ -674,18 +674,20 @@ static void dasd_profile_start(struct dasd_block *block,
* we count each request only once.
*/
device = cqr->startdev;
- if (device->profile.data) {
- counter = 1; /* request is not yet queued on the start device */
- list_for_each(l, &device->ccw_queue)
- if (++counter >= 31)
- break;
- }
+ if (!device->profile.data)
+ return;
+
+ spin_lock(get_ccwdev_lock(device->cdev));
+ counter = 1; /* request is not yet queued on the start device */
+ list_for_each(l, &device->ccw_queue)
+ if (++counter >= 31)
+ break;
+ spin_unlock(get_ccwdev_lock(device->cdev));
+
spin_lock(&device->profile.lock);
- if (device->profile.data) {
- device->profile.data->dasd_io_nr_req[counter]++;
- if (rq_data_dir(req) == READ)
- device->profile.data->dasd_read_nr_req[counter]++;
- }
+ device->profile.data->dasd_io_nr_req[counter]++;
+ if (rq_data_dir(req) == READ)
+ device->profile.data->dasd_read_nr_req[counter]++;
spin_unlock(&device->profile.lock);
}
--
2.39.2
