bpf: Reject untrusted allocated-object pointers

Summary

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 ]

Timeline

1. Sep 25, 2026, 10:23 AM UTCCVE published
2. Oct 19, 2026, 9:12 AM UTCRecord last updated

Affected versions

• Linux Linux

  From 1b12171533a9bb23cf6fba7262b479028b65e1e8 · fixed in 092c2874dc1b2060fa77a465a971acd4fdf87683; From 1b12171533a9bb23cf6fba7262b479028b65e1e8 · fixed in 135d542b97fa93e32c457d49d6e7b33ca7d05bae; From 1b12171533a9bb23cf6fba7262b479028b65e1e8 · fixed in 6b1f786ad85a0b63393b76f5e634deab1a73198c; From 1b12171533a9bb23cf6fba7262b479028b65e1e8 · fixed in 7441ee8276641bddaf1cba7bb75ef9c1458ceb3b

• Linux Linux

  6.8

• KernelLinux

  From 6.8.0 · fixed in 6.12.111; From 6.13.0 · fixed in 6.18.53; From 6.19.0 · fixed in 7.2.7

References 4