Bug 2297493 (CVE-2024-40909)

Summary: CVE-2024-40909 kernel: bpf: Fix a potential use-after-free in bpf_link_free()
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: unspecifiedCC: dfreiber, drow, jburrell, vkumar
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
Whiteboard:
Fixed In Version: kernel 6.6.35, kernel 6.9.6, kernel 6.10-rc3 Doc Type: If docs needed, set a value
Doc Text:
The Linux kernel vulnerability related to `bpf_link_free()` involved a potential use-after-free condition. After commit `1a80dbcb2dba`, the `bpf_link` could be freed via `link->ops->dealloc_deferred`, but the code erroneously continued to reference `link->ops->dealloc`. This dual reference risked accessing freed memory, leading to undefined behavior.
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Description OSIDB Bzimport 2024-07-12 13:27:07 UTC 
In the Linux kernel, the following vulnerability has been resolved:

bpf: Fix a potential use-after-free in bpf_link_free()

After commit 1a80dbcb2dba, bpf_link can be freed by
link->ops->dealloc_deferred, but the code still tests and uses
link->ops->dealloc afterward, which leads to a use-after-free as
reported by syzbot. Actually, one of them should be sufficient, so
just call one of them instead of both. Also add a WARN_ON() in case
of any problematic implementation.