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.

• linux linux kernel (>= 6.3.9 < 6.4) • linux linux kernel (>= 6.4.1 < 6.6.144) • linux linux kernel (>= 6.7 < 6.12.95) • linux linux kernel (>= 6.13 < 6.18.38) • linux linux kernel (>= 6.19 < 7.1.3) • linux linux kernel 6.4