[PATCH v4 bpf-next 1/6] bpf: Allow kfuncs return 'void *'

[Alexei Starovoitov <alexei.starovoitov@xxxxxxxxx>]

From: Alexei Starovoitov <ast@xxxxxxxxxx>

Recognize return of 'void *' from kfunc as returning unknown scalar.

Acked-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
Acked-by: Kumar Kartikeya Dwivedi <memxor@xxxxxxxxx>
Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx>
---
 kernel/bpf/verifier.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index ee86e4d7d5fc..9c2a36b1373b 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -12364,6 +12364,9 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
 					meta.func_name);
 				return -EFAULT;
 			}
+		} else if (btf_type_is_void(ptr_type)) {
+			/* kfunc returning 'void *' is equivalent to returning scalar */
+			mark_reg_unknown(env, regs, BPF_REG_0);
 		} else if (!__btf_type_is_struct(ptr_type)) {
 			if (!meta.r0_size) {
 				__u32 sz;
-- 
2.43.0