Bug 2548397 (CVE-2026-98376)

Summary: CVE-2026-98376 kernel: bpf: Use array_map_meta_equal for percpu array inner map replacement
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: 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) subsystem. When replacing an inner per-CPU array map within a map-in-map structure, the kernel fails to verify that the replacement map matches the size of the original template map. A local attacker can exploit this flaw by substituting an inner map with one that has fewer entries, causing subsequent lookups to perform out-of-bounds memory access. This issue can lead to kernel memory corruption, resulting in a system crash (Denial of Service) or potential privilege escalation.
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Description OSIDB Bzimport 2026-10-09 08:01:51 UTC 
In the Linux kernel, the following vulnerability has been resolved:

bpf: Use array_map_meta_equal for percpu array inner map replacement

percpu_array_map_ops.map_meta_equal points to the generic
bpf_map_meta_equal(), which does not compare max_entries.  When a
percpu array serves as an inner map, replacing it with one that has
fewer max_entries bypasses the check.  Since percpu_array_map_gen_lookup()
inlines the original template's index_mask as a JIT immediate, a lookup
on the replacement map can access pptrs[] out of bounds.

Point percpu_array_map_ops.map_meta_equal to array_map_meta_equal(),
which already enforces the max_entries equality check.

Add a selftest to verify that replacing a percpu array inner map with
a differently-sized one is rejected.
Comment 1 gkamathe 2026-10-10 15:03:50 UTC 
Upstream advisory:
https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-98376.mbox