Bug 2536440 (CVE-2026-93138) - CVE-2026-93138 kernel: bpf: Fix vmlinux BTF prep race in bpf_get_btf_vmlinux
Summary: CVE-2026-93138 kernel: bpf: Fix vmlinux BTF prep race in bpf_get_btf_vmlinux
Keywords:
Status: NEW
Alias: CVE-2026-93138
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
medium
medium
Target Milestone: ---
Assignee: Product Security
QA Contact:
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2026-09-17 17:53 UTC by OSIDB Bzimport
Modified: 2026-10-20 11:42 UTC (History)
17 users (show)

Fixed In Version:
Clone Of:
Environment:
Last Closed:
Embargoed:


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Description OSIDB Bzimport 2026-09-17 17:53:03 UTC
In the Linux kernel, the following vulnerability has been resolved:

bpf: Fix vmlinux BTF prep race in bpf_get_btf_vmlinux

bpf_get_btf_vmlinux() lazily parses the vmlinux BTF under the
bpf_verifier_lock, but publishes the result through a plain store
and re-checks it through a plain lockless load. Nothing orders
the stores initializing the struct btf inside btf_parse_vmlinux()
against the store publishing the pointer: On a weakly ordered
arch, a concurrent first-time caller taking the lockless fast
path could in principle observe the pointer before the parsed
contents are visible. The mutex_unlock() does not help such a
reader given it only synchronizes with a later acquisition of the
same lock. Thus, publish the pointer with smp_store_release()
and read it on the fast path with smp_load_acquire().

Acquire semantics are needed rather than a dependency-ordered
READ_ONCE(): btf_parse_vmlinux() also populates globals outside
the returned object (e.g. bpf_ctx_convert.t). An address
dependency would only order accesses performed through the
pointer and not cover other globals.


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