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bpf: Add KF_RCU flag to bpf_refcount_acquire_impl
Refcounted local kptrs are kptrs to user-defined types with a bpf_refcount field. Recent commits ([0], [1]) modified the lifetime of refcounted local kptrs such that the underlying memory is not reused until RCU grace period has elapsed. Separately, verification of bpf_refcount_acquire calls currently succeeds for MAYBE_NULL non-owning reference input, which is a problem as bpf_refcount_acquire_impl has no handling for this case. This patch takes advantage of aforementioned lifetime changes to tag bpf_refcount_acquire_impl kfunc KF_RCU, thereby preventing MAYBE_NULL input to the kfunc. The KF_RCU flag applies to all kfunc params; it's fine for it to apply to the void *meta__ign param as that's populated by the verifier and is tagged __ign regardless. [0]: commit7e26cd12ad
("bpf: Use bpf_mem_free_rcu when bpf_obj_dropping refcounted nodes") is the actual change to allocation behaivor [1]: commit0816b8c6bf
("bpf: Consider non-owning refs to refcounted nodes RCU protected") modified verifier understanding of refcounted local kptrs to match [0]'s changes Signed-off-by: Dave Marchevsky <davemarchevsky@fb.com> Fixes:7c50b1cb76
("bpf: Add bpf_refcount_acquire kfunc") Link: https://lore.kernel.org/r/20231107085639.3016113-2-davemarchevsky@fb.com Signed-off-by: Alexei Starovoitov <ast@kernel.org>
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@ -2520,7 +2520,7 @@ BTF_ID_FLAGS(func, bpf_obj_new_impl, KF_ACQUIRE | KF_RET_NULL)
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BTF_ID_FLAGS(func, bpf_percpu_obj_new_impl, KF_ACQUIRE | KF_RET_NULL)
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BTF_ID_FLAGS(func, bpf_obj_drop_impl, KF_RELEASE)
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BTF_ID_FLAGS(func, bpf_percpu_obj_drop_impl, KF_RELEASE)
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BTF_ID_FLAGS(func, bpf_refcount_acquire_impl, KF_ACQUIRE | KF_RET_NULL)
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BTF_ID_FLAGS(func, bpf_refcount_acquire_impl, KF_ACQUIRE | KF_RET_NULL | KF_RCU)
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BTF_ID_FLAGS(func, bpf_list_push_front_impl)
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BTF_ID_FLAGS(func, bpf_list_push_back_impl)
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BTF_ID_FLAGS(func, bpf_list_pop_front, KF_ACQUIRE | KF_RET_NULL)
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