Commit 403ebc87 authored by Ming Lei's avatar Ming Lei Committed by Jens Axboe
Browse files

ublk_drv: add module parameter of ublks_max for limiting max allowed ublk dev 



Prepare for supporting unprivileged ublk device by limiting max number
ublk devices added. Otherwise too many ublk devices could be added by
un-trusted user, which can be thought as one DoS.

Reviewed-by: default avatarZiyangZhang <ZiyangZhang@linux.alibaba.com>
Signed-off-by: default avatarMing Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20230106041711.914434-6-ming.lei@redhat.com


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent abb864d3

drivers/block/ublk_drv.c

+19 −0
Original line number Diff line number Diff line
@@ -186,6 +186,15 @@ static wait_queue_head_t ublk_idr_wq; /* wait until one idr is freed */ 


static DEFINE_MUTEX(ublk_ctl_mutex);



/*

 * Max ublk devices allowed to add

 *

 * It can be extended to one per-user limit in future or even controlled

 * by cgroup.

 */

static unsigned int ublks_max = 64;

static unsigned int ublks_added;	/* protected by ublk_ctl_mutex */



static struct miscdevice ublk_misc;



static void ublk_dev_param_basic_apply(struct ublk_device *ub)
@@ -1441,6 +1450,8 @@ static int ublk_add_chdev(struct ublk_device *ub) 
	ret = cdev_device_add(&ub->cdev, dev);

	if (ret)

		goto fail;



	ublks_added++;

	return 0;

 fail:

	put_device(dev);
@@ -1483,6 +1494,7 @@ static void ublk_remove(struct ublk_device *ub) 
	cancel_work_sync(&ub->quiesce_work);

	cdev_device_del(&ub->cdev, &ub->cdev_dev);

	put_device(&ub->cdev_dev);

	ublks_added--;

}



static struct ublk_device *ublk_get_device_from_id(int idx)
@@ -1642,6 +1654,10 @@ static int ublk_ctrl_add_dev(struct io_uring_cmd *cmd) 
	if (ret)

		return ret;



	ret = -EACCES;

	if (ublks_added >= ublks_max)

		goto out_unlock;



	ret = -ENOMEM;

	ub = kzalloc(sizeof(*ub), GFP_KERNEL);

	if (!ub)
@@ -2095,5 +2111,8 @@ static void __exit ublk_exit(void) 
module_init(ublk_init);

module_exit(ublk_exit);



module_param(ublks_max, int, 0444);

MODULE_PARM_DESC(ublks_max, "max number of ublk devices allowed to add(default: 64)");



MODULE_AUTHOR("Ming Lei <ming.lei@redhat.com>");

MODULE_LICENSE("GPL");