Commit 7faccdf4 authored by Martin KaFai Lau's avatar Martin KaFai Lau Committed by Alexei Starovoitov
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bpf: Simplify reg0 marking for the rbtree kfuncs that return a bpf_rb_node pointer 



The current rbtree kfunc, bpf_rbtree_{first, remove}, returns the
bpf_rb_node pointer. The check_kfunc_call currently checks the
kfunc btf_id instead of its return pointer type to decide
if it needs to do mark_reg_graph_node(reg0) and ref_set_non_owning(reg0).

The later patch will add bpf_rbtree_{root,left,right} that will also
return a bpf_rb_node pointer. Instead of adding more kfunc btf_id
checks to the "if" case, this patch changes the test to check the
kfunc's return type. is_rbtree_node_type() function is added to
test if a pointer type is a bpf_rb_node. The callers have already
skipped the modifiers of the pointer type.

A note on the ref_set_non_owning(), although bpf_rbtree_remove()
also returns a bpf_rb_node pointer, the bpf_rbtree_remove()
has the KF_ACQUIRE flag. Thus, its reg0 will not become non-owning.

Acked-by: default avatarKumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: default avatarMartin KaFai Lau <martin.lau@kernel.org>
Link: https://lore.kernel.org/r/20250506015857.817950-3-martin.lau@linux.dev


Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent b183c012

kernel/bpf/verifier.c

+7 −3
Original line number Diff line number Diff line
@@ -11987,6 +11987,11 @@ static bool is_kfunc_arg_res_spin_lock(const struct btf *btf, const struct btf_p 
	return __is_kfunc_ptr_arg_type(btf, arg, KF_ARG_RES_SPIN_LOCK_ID);

}









static bool is_rbtree_node_type(const struct btf_type *t)









{









	return t == btf_type_by_id(btf_vmlinux, kf_arg_btf_ids[KF_ARG_RB_NODE_ID]);









}

















static bool is_kfunc_arg_callback(struct bpf_verifier_env *env, const struct btf *btf,









				  const struct btf_param *arg)









{








@@ -13750,8 +13755,7 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,







				struct btf_field *field = meta.arg_list_head.field;

















				mark_reg_graph_node(regs, BPF_REG_0, &field->graph_root);









			} else if (meta.func_id == special_kfunc_list[KF_bpf_rbtree_remove] ||









				   meta.func_id == special_kfunc_list[KF_bpf_rbtree_first]) {









			} else if (is_rbtree_node_type(ptr_type)) {









				struct btf_field *field = meta.arg_rbtree_root.field;

















				mark_reg_graph_node(regs, BPF_REG_0, &field->graph_root);








@@ -13881,7 +13885,7 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,







			if (is_kfunc_ret_null(&meta))









				regs[BPF_REG_0].id = id;









			regs[BPF_REG_0].ref_obj_id = id;









		} else if (meta.func_id == special_kfunc_list[KF_bpf_rbtree_first]) {









		} else if (is_rbtree_node_type(ptr_type)) {









			ref_set_non_owning(env, &regs[BPF_REG_0]);









		}