Bug 2425208 (CVE-2023-54107)

Summary: CVE-2023-54107 kernel: Linux kernel blk-cgroup: Use-after-free vulnerability leading to denial of service
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedKeywords: Security
Target Milestone: ---   
Target Release: ---   
Hardware: All   
OS: Linux   
Whiteboard:
Fixed In Version: Doc Type: ---
Doc Text:
A flaw was found in the Linux kernel's block cgroup (blk-cgroup) component. A local attacker, by creating and tearing down cgroups and triggering block cgroup policy activity, could exploit a use-after-free vulnerability. This occurs due to the asynchronous execution of `pd_free_fn`, which can prematurely free parent policy data while child policies may still access it. This could lead to a stale pointer dereference, potentially causing a denial of service (DoS).
 Story Points: ---
Clone Of: Environment:
Last Closed: Type: ---
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:

Description OSIDB Bzimport 2025-12-24 14:10:54 UTC 
In the Linux kernel, the following vulnerability has been resolved:

blk-cgroup: dropping parent refcount after pd_free_fn() is done

Some cgroup policies will access parent pd through child pd even
after pd_offline_fn() is done. If pd_free_fn() for parent is called
before child, then UAF can be triggered. Hence it's better to guarantee
the order of pd_free_fn().

Currently refcount of parent blkg is dropped in __blkg_release(), which
is before pd_free_fn() is called in blkg_free_work_fn() while
blkg_free_work_fn() is called asynchronously.

This patch make sure pd_free_fn() called from removing cgroup is ordered
by delaying dropping parent refcount after calling pd_free_fn() for
child.

BTW, pd_free_fn() will also be called from blkcg_deactivate_policy()
from deleting device, and following patches will guarantee the order.
Comment 1 Alexander B 2025-12-24 18:37:47 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2025122412-CVE-2023-54107-12ef@gregkh/T