In the Linux kernel, the following vulnerability has been resolved:
clsact: Fix use-after-free in init/destroy rollback asymmetry
Fix a use-after-free in the clsact qdisc upon init/destroy rollback asymmetry.
The latter is achieved by first fully initializing a clsact instance, and
then in a second step having a replacement failure for the new clsact qdisc
instance. clsact_init() initializes ingress first and then takes care of the
egress part. This can fail midway, for example, via tcf_block_get_ext(). Upon
failure, the kernel will trigger the clsact_destroy() callback.
Commit 1cb6f0bae504 ("bpf: Fix too early release of tcx_entry") details the
way how the transition is happening. If tcf_block_get_ext on the q->ingress_block
ends up failing, we took the tcx_miniq_inc reference count on the ingress
side, but not yet on the egress side. clsact_destroy() tests whether the
{ingress,egress}_entry was non-NULL. However, even in midway failure on the
replacement, both are in fact non-NULL with a valid egress_entry from the
previous clsact instance.
What we really need to test for is whether the qdisc instance-specific ingress
or egress side previously got initialized. This adds a small helper for checking
the miniq initialization called mini_qdisc_pair_inited, and utilizes that upon
clsact_destroy() in order to fix the use-after-free scenario. Convert the
ingress_destroy() side as well so both are consistent to each other.
References
Configurations
Configuration 1 (hide)
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History
No history.
Information
Published : 2026-04-02 12:16
Updated : 2026-06-17 10:21
NVD link : CVE-2026-23413
Mitre link : CVE-2026-23413
CVE.ORG link : CVE-2026-23413
JSON object : View
Products Affected
linux
- linux_kernel
CWE
CWE-416
Use After Free