Bug 2540368 (CVE-2026-93270)

Summary:	CVE-2026-93270 kernel: bpf: Disallow interpreter fallback for BPF_ADDR_PERCPU insn
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security DevOps Team <prodsec-dev>
Status:	NEW ---	QA Contact:
Severity:	medium	Docs Contact:
Priority:	medium
Version:	unspecified	CC:	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
Whiteboard:
Fixed In Version:		Doc Type:	---
Doc Text:	A flaw was found in the Linux kernel's Berkeley Packet Filter (BPF) subsystem. When the BPF interpreter processes specific per-CPU instructions instead of using Just-In-Time (JIT) compilation, it fails to properly handle memory offset calculations. A local user could exploit this flaw by loading a crafted BPF program, causing an unhandled kernel page fault that leads to a system crash and 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 2026-09-24 16:24:22 UTC

In the Linux kernel, the following vulnerability has been resolved:

bpf: Disallow interpreter fallback for BPF_ADDR_PERCPU insn

The BPF_MOV64_PERCPU_REG insn requires JIT to emit native code to for
'dst_reg = src_reg + <percpu_base_off>'.

However, the interpreter ignores the 'off' at its ALU64_MOV_X label.
The 'off' indicates the insn is BPF_MOV64_PERCPU_REG insn. Then, when
the interpreter loads memory from the register, it will hit a page
fault.

[    2.545572] BUG: unable to handle page fault for address: ffffffffacaaf034
[    2.546485] #PF: supervisor read access in kernel mode
[    2.547167] #PF: error_code(0x0000) - not-present page
[    2.547850] PGD 134e63067 P4D 134e63067 PUD 134e64063 PMD 10021c063 PTE 800ffffeca550062
[    2.548912] Oops: Oops: 0000 [#1] SMP PTI

Set jit_required as true in order to disallow interpreter fallback in
core.c::__bpf_prog_select_runtime(), if any BPF_ADDR_PERCPU insn is
patched to the prog.

BTW, rename the helper bpf_map_supports_cpu_flags() to
bpf_map_is_percpu_map().

Comment 1 gkamathe 2026-09-28 12:11:04 UTC

Upstream advisory:
https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-93270.mbox