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s390/dasd: protect device queue against concurrent access

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commit db46cd1e0426f52999d50fa72cfa97fa39952885 upstream.

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@vger.kernel.org>
Fixes: 4fa52aa7a82f ("[S390] dasd: add enhanced DASD statistics interface")
Reviewed-by: Stefan Haberland <sth@linux.ibm.com>
Signed-off-by: Jan Höppner <hoeppner@linux.ibm.com>
Signed-off-by: Stefan Haberland <sth@linux.ibm.com>
Link: https://lore.kernel.org/r/20231025132437.1223363-3-sth@linux.ibm.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Jan Höppner 2023-10-25 15:24:37 +02:00 • committed by Ksawlii
parent 475bd70f75
commit 71394ac071
1 changed files with 13 additions and 11 deletions
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24
drivers/s390/block/dasd.c
View file

@ -737,18 +737,20 @@ 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);
}