CVE-2026-63802

Summary

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.

Affected Software

VendorProductVersion RangeStatus
LinuxLinux20cb1c2fb7568a6054c55defe044311397e01ddb < 96e545410c4f74c89d496c1d5d9ef8d08f14368baffected
LinuxLinux20cb1c2fb7568a6054c55defe044311397e01ddb < bbebd9425cad3573d1527441753899b926525a0faffected
LinuxLinux20cb1c2fb7568a6054c55defe044311397e01ddb < 5e5b7f2ef854936e95dceb6a2fdfefcb7152d2c6affected
LinuxLinux20cb1c2fb7568a6054c55defe044311397e01ddb < afebe44facc48a61761e885bbb7f0380d4a603ecaffected
LinuxLinux20cb1c2fb7568a6054c55defe044311397e01ddb < 0ab5ee5a1badb58cbb2242617cb01a4972b1f2a2affected
LinuxLinux0f6090d90f627d8c58f939067d6c6821ce1b3c68affected
LinuxLinux6.3.9 < 6.4affected
LinuxLinux6.4affected
LinuxLinux0 < 6.4unaffected
LinuxLinux6.6.144 <= 6.6.*unaffected
LinuxLinux6.12.95 <= 6.12.*unaffected
LinuxLinux6.18.38 <= 6.18.*unaffected
LinuxLinux7.1.3 <= 7.1.*unaffected
LinuxLinux7.2-rc1 <= *unaffected

Weaknesses

References