CVE-2026-63802

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

blk-cgroup: fix UAF in __blkcg_rstat_flush()

When multiple blkgs in the same blkcg are released concurrently,

a use-after-free can occur. The race happens when one blkg's

__blkcg_rstat_flush() removes another blkg's iostat entries via

llist_del_all(). The second blkg sees an empty list and proceeds

to free itself while the first is still iterating over its entries.

Move the flush from __blkg_release() (RCU callback) to blkg_release()

(before call_rcu). This ensures the RCU grace period waits for any

concurrent flush's rcu_read_lock() section to complete before freeing.