CVE-2025-21631 block, bfq: fix waker_bfqq UAF after bfq_split_bfqq()

In the Linux kernel, the following vulnerability has been resolved: block, bfq: fix wakerbfqq UAF after bfqsplitbfqq Our syzkaller report a following UAF for v6.6: BUG: KASAN: slab-use-after-free in bfqinitrq+0x175d/0x17a0 block/bfq-iosched.c:6958 Read of size 8 at addr ffff8881b57147d8 by task...