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

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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: ZiyangZhang <ZiyangZhang@linux.alibaba.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20230106041711.914434-6-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Ming Lei 2023-01-06 12:17:10 +08:00 committed by Jens Axboe
parent abb864d380
commit 403ebc8778
1 changed files with 19 additions and 0 deletions
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19
drivers/block/ublk_drv.c
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@ -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");