ublk_drv: fix error handling of ublk_add_dev

__ublk_destroy_dev() is called for handling error in ublk_add_dev(),
but either tagset isn't allocated or mutex isn't initialized.

So fix the issue by letting replacing ublk_add_dev with a
ublk_add_tag_set function that is much more limited in scope and
instead unwind every single step directly in ublk_ctrl_add_dev.
To allow for this refactor the device freeing so that there is
a helper for freeing the device number instead of coupling that
with freeing the mutex and the memory.

Note that this now copies the dev_info to userspace before adding
the character device.  This not only simplifies the erro handling
in ublk_ctrl_add_dev, but also means that the character device
can only be seen by userspace if the device addition succeeded.

Based on a patch from Ming Lei.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20220722103817.631258-2-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c
index f058f40..67f91a8 100644 (file)
--- a/drivers/block/ublk_drv.c
+++ b/drivers/block/ublk_drv.c
@@ -1005,7 +1005,7 @@ static int ublk_init_queues(struct ublk_device *ub)
        return ret;
 }
 
-static int __ublk_alloc_dev_number(struct ublk_device *ub, int idx)
+static int ublk_alloc_dev_number(struct ublk_device *ub, int idx)
 {
        int i = idx;
        int err;
@@ -1027,16 +1027,12 @@ static int __ublk_alloc_dev_number(struct ublk_device *ub, int idx)
        return err;
 }
 
-static void __ublk_destroy_dev(struct ublk_device *ub)
+static void ublk_free_dev_number(struct ublk_device *ub)
 {
        spin_lock(&ublk_idr_lock);
        idr_remove(&ublk_index_idr, ub->ub_number);
        wake_up_all(&ublk_idr_wq);
        spin_unlock(&ublk_idr_lock);
-
-       mutex_destroy(&ub->mutex);
-
-       kfree(ub);
 }
 
 static void ublk_cdev_rel(struct device *dev)
@@ -1045,8 +1041,9 @@ static void ublk_cdev_rel(struct device *dev)
 
        blk_mq_free_tag_set(&ub->tag_set);
        ublk_deinit_queues(ub);
-
-       __ublk_destroy_dev(ub);
+       ublk_free_dev_number(ub);
+       mutex_destroy(&ub->mutex);
+       kfree(ub);
 }
 
 static int ublk_add_chdev(struct ublk_device *ub)
@@ -1092,24 +1089,8 @@ static void ublk_align_max_io_size(struct ublk_device *ub)
                round_down(max_rq_bytes, PAGE_SIZE) >> ub->bs_shift;
 }
 
-/* add tag_set & cdev, cleanup everything in case of failure */
-static int ublk_add_dev(struct ublk_device *ub)
+static int ublk_add_tag_set(struct ublk_device *ub)
 {
-       int err = -ENOMEM;
-
-       /* We are not ready to support zero copy */
-       ub->dev_info.flags[0] &= ~UBLK_F_SUPPORT_ZERO_COPY;
-
-       ub->bs_shift = ilog2(ub->dev_info.block_size);
-       ub->dev_info.nr_hw_queues = min_t(unsigned int,
-                       ub->dev_info.nr_hw_queues, nr_cpu_ids);
-
-       INIT_WORK(&ub->stop_work, ublk_stop_work_fn);
-       INIT_DELAYED_WORK(&ub->monitor_work, ublk_daemon_monitor_work);
-
-       if (ublk_init_queues(ub))
-               goto out_destroy_dev;
-
        ub->tag_set.ops = &ublk_mq_ops;
        ub->tag_set.nr_hw_queues = ub->dev_info.nr_hw_queues;
        ub->tag_set.queue_depth = ub->dev_info.queue_depth;
@@ -1117,22 +1098,7 @@ static int ublk_add_dev(struct ublk_device *ub)
        ub->tag_set.cmd_size = sizeof(struct ublk_rq_data);
        ub->tag_set.flags = BLK_MQ_F_SHOULD_MERGE;
        ub->tag_set.driver_data = ub;
-       err = blk_mq_alloc_tag_set(&ub->tag_set);
-       if (err)
-               goto out_deinit_queues;
-
-       ublk_align_max_io_size(ub);
-       mutex_init(&ub->mutex);
-       spin_lock_init(&ub->mm_lock);
-
-       /* add char dev so that ublksrv daemon can be setup */
-       return ublk_add_chdev(ub);
-
-out_deinit_queues:
-       ublk_deinit_queues(ub);
-out_destroy_dev:
-       __ublk_destroy_dev(ub);
-       return err;
+       return blk_mq_alloc_tag_set(&ub->tag_set);
 }
 
 static void ublk_remove(struct ublk_device *ub)
@@ -1318,26 +1284,56 @@ static int ublk_ctrl_add_dev(struct io_uring_cmd *cmd)
        ub = kzalloc(sizeof(*ub), GFP_KERNEL);
        if (!ub)
                goto out_unlock;
+       mutex_init(&ub->mutex);
+       spin_lock_init(&ub->mm_lock);
+       INIT_WORK(&ub->stop_work, ublk_stop_work_fn);
+       INIT_DELAYED_WORK(&ub->monitor_work, ublk_daemon_monitor_work);
 
-       ret = __ublk_alloc_dev_number(ub, header->dev_id);
-       if (ret < 0) {
-               kfree(ub);
-               goto out_unlock;
-       }
+       ret = ublk_alloc_dev_number(ub, header->dev_id);
+       if (ret < 0)
+               goto out_free_ub;
 
        memcpy(&ub->dev_info, &info, sizeof(info));
 
        /* update device id */
        ub->dev_info.dev_id = ub->ub_number;
 
-       ret = ublk_add_dev(ub);
+       /* We are not ready to support zero copy */
+       ub->dev_info.flags[0] &= ~UBLK_F_SUPPORT_ZERO_COPY;
+
+       ub->bs_shift = ilog2(ub->dev_info.block_size);
+       ub->dev_info.nr_hw_queues = min_t(unsigned int,
+                       ub->dev_info.nr_hw_queues, nr_cpu_ids);
+       ublk_align_max_io_size(ub);
+
+       ret = ublk_init_queues(ub);
        if (ret)
-               goto out_unlock;
+               goto out_free_dev_number;
 
-       if (copy_to_user(argp, &ub->dev_info, sizeof(info))) {
-               ublk_remove(ub);
-               ret = -EFAULT;
-       }
+       ret = ublk_add_tag_set(ub);
+       if (ret)
+               goto out_deinit_queues;
+
+       ret = -EFAULT;
+       if (copy_to_user(argp, &ub->dev_info, sizeof(info)))
+               goto out_free_tag_set;
+
+       /*
+        * Add the char dev so that ublksrv daemon can be setup.
+        * ublk_add_chdev() will cleanup everything if it fails.
+        */
+       ret = ublk_add_chdev(ub);
+       goto out_unlock;
+
+out_free_tag_set:
+       blk_mq_free_tag_set(&ub->tag_set);
+out_deinit_queues:
+       ublk_deinit_queues(ub);
+out_free_dev_number:
+       ublk_free_dev_number(ub);
+out_free_ub:
+       mutex_destroy(&ub->mutex);
+       kfree(ub);
 out_unlock:
        mutex_unlock(&ublk_ctl_mutex);
        return ret;