Bug 2536630 (CVE-2026-90313)

Summary: CVE-2026-90313 kernel: bpf, cgroup: Fix invalid storage access after __cgroup_bpf_attach failed
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: akhatavk, aos-team-art-private, asdas, dpaolell, jdelft, jupierce, lgarciaa, mbiarnes, ppalepu, ppostler, prdhamdh, rhel-process-autobot, sghai, sidsharm, suppawar, vlaad, watson-tool-maintainers
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
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A flaw was found in the Linux kernel's BPF (Berkeley Packet Filter) cgroup functionality. This issue arises during the replacement of a cgroup BPF program in multi-attach mode. If the replacement process fails, the system may not correctly restore the original program's storage pointers, leaving them in an invalid or dangling state. This can lead to an invalid memory access when the affected program attempts to use its local storage, potentially causing system instability or a denial of service.
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Description OSIDB Bzimport 2026-09-17 18:58:09 UTC 
In the Linux kernel, the following vulnerability has been resolved:

bpf, cgroup: Fix invalid storage access after __cgroup_bpf_attach failed

A potential invalid storage access issue can occur after replacing a
cgroup bpf prog.

This occurs in the following scenario:
1. prog1 with storage is attached to a cgroup in multi-attach mode.
2. prog1 is replaced with prog2 using BPF_F_REPLACE in multi-attach
   mode, but fails midway (e.g. in bpf_trampoline_link_cgroup_shim or
   update_effective_progs).
3. A new prog3 is attached to the cgroup in multi-attach mode.

The reason is that __cgroup_bpf_attach overwrites pl->storage with the
new storage prior to attachment completion. When attachment fails
midway, the cleanup path calls bpf_cgroup_storages_free(new_storage) to
free the newly allocated storage, but fails to restore pl->storage back
to old_storage.

Consequently, the still-active prog1 holds invalid or dangling storage
pointers, leading to an invalid memory access when prog1 executes and
calls bpf_get_local_storage. Additionally, original pl->flags and
cgrp->bpf.flags[atype] are left unrestored.

Fix this by saving old_pl_flags, old_storage, and old_flags prior to the
update, and properly restoring all of them in the cleanup path on error.
Comment 1 gkamathe 2026-09-23 06:02:29 UTC 
Upstream advisory:
https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-90313.mbox