In the Linux kernel, the following vulnerability has been resolved: blk-mq: fix tags leak when...

In the Linux kernel, the following vulnerability has been resolved:

blk-mq: fix tags leak when shrink nr_hw_queues

Although we don't need to realloc set->tags[] when shrink nr_hw_queues, we need to free them. Or these tags will be leaked.

How to reproduce:

1. mount -t configfs configfs /mnt
2. modprobe null_blk nr_devices=0 submit_queues=8
3. mkdir /mnt/nullb/nullb0
4. echo 1 > /mnt/nullb/nullb0/power
5. echo 4 > /mnt/nullb/nullb0/submit_queues
6. rmdir /mnt/nullb/nullb0

In step 4, will alloc 9 tags (8 submit queues and 1 poll queue), then in step 5, new_nr_hw_queues = 5 (4 submit queues and 1 poll queue). At last in step 6, only these 5 tags are freed, the other 4 tags leaked.