bpf: Keep refcount_acquire nullable for borrowed RCU kptrs

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-98038
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-09-25 11:17:32 UTC
Updated2026-09-25 11:17:32 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: bpf: Keep refcount_acquire nullable for borrowed RCU kptrs bpf_refcount_acquire() is fallible for a borrowed reference because the object may have reached a zero refcount. The verifier therefore keeps KF_RET_NULL on the return value unless the argument is an owning reference. An RCU-protected load of a local kptr is marked MEM_ALLOC, but it only receives NON_OWN_REF when the pointee contains a graph node. A refcounted object without a graph node consequently looks like an owning reference even though the loaded register has no acquired reference state. If the program drops the last real reference while remaining in the RCU critical section, refcount_inc_not_zero() returns NULL while the verifier treats the result as non-NULL. Only classify the argument as owning when it is backed by a verifier-tracked reference. This retains the non-NULL return for pointers from bpf_obj_new(), bpf_kptr_xchg(), or an earlier successful acquisition, while requiring a NULL check for borrowed RCU kptrs. [ kkd: Rewrote commit log ]

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 1b12171533a9bb23cf6fba7262b479028b65e1e8 85074498228a2500ea8b8039c49cc1ab8ad5328f git Not specified
CNA Linux Linux affected 1b12171533a9bb23cf6fba7262b479028b65e1e8 dc36739e5cc9f60485418a910b42bc95339218d2 git Not specified
CNA Linux Linux affected 6.8 Not specified
CNA Linux Linux unaffected 6.8 semver Not specified
CNA Linux Linux unaffected 7.2.7 7.2.* semver Not specified
CNA Linux Linux unaffected 7.3-rc2 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/dc36739e5cc9f60485418a910b42bc95339218d2 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/85074498228a2500ea8b8039c49cc1ab8ad5328f 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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