CVE-2026-98037

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

bpf: Reject untrusted allocated-object pointers

When the final RCU read-side critical section ends, a local kptr is demoted to PTR_UNTRUSTED but retains MEM_ALLOC. The pointer may be NULL or may refer to an object whose lifetime is no longer protected.

type_is_ptr_alloc_obj() nevertheless recognizes any PTR_TO_BTF_ID with MEM_ALLOC as a live allocated object. In particular, a refcount-only local kptr never carries NON_OWN_REF, so it still passes the bpf_refcount_acquire() argument check after RCU protection ends. The kfunc can then dereference NULL or stale memory.

Make type_is_ptr_alloc_obj() reject PTR_UNTRUSTED pointers. Since type_is_non_owning_ref() is based on the same predicate, graph kfunc arguments obey the same live-object requirement. Fault-protected reads of the demoted pointer remain valid: writes are already rejected, and read fixups use bpf_may_fault_on_deref() rather than this predicate.

[ kkd: Rewrote commit log ]

Affected Software

References

• https://git.kernel.org/stable/c/092c2874dc1b2060fa77a465a971acd4fdf87683
• https://git.kernel.org/stable/c/135d542b97fa93e32c457d49d6e7b33ca7d05bae
• https://git.kernel.org/stable/c/6b1f786ad85a0b63393b76f5e634deab1a73198c
• https://git.kernel.org/stable/c/7441ee8276641bddaf1cba7bb75ef9c1458ceb3b