From: Jan Höppner dasd_release_space() checks the implementation of the is_ese() discipline function before calling it to determine if a given device is an ESE DASD. The current usage of the logical AND operator will lead to a NULL pointer dereference as the function is called even if the function pointer is NULL. Fix this by using the logical OR operator. Fixes: 91dc4a197569 ("s390/dasd: Add new ioctl to release space") Cc: stable@vger.kernel.org # v5.3+ Reported-by: Vasily Gorbik Acked-by: Eduard Shishkin Reviewed-by: Stefan Haberland Signed-off-by: Jan Höppner Signed-off-by: Stefan Haberland --- drivers/s390/block/dasd_ioctl.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/s390/block/dasd_ioctl.c b/drivers/s390/block/dasd_ioctl.c index c85ee42732a3..e5b8b413f5ab 100644 --- a/drivers/s390/block/dasd_ioctl.c +++ b/drivers/s390/block/dasd_ioctl.c @@ -324,7 +324,7 @@ static int dasd_ioctl_check_format(struct block_device *bdev, void __user *argp) static int dasd_release_space(struct dasd_device *device, struct format_data_t *rdata) { - if (!device->discipline->is_ese && !device->discipline->is_ese(device)) + if (!device->discipline->is_ese || !device->discipline->is_ese(device)) return -ENOTSUPP; if (!device->discipline->release_space) return -ENOTSUPP; -- 2.53.0