From: Alexei Starovoitov <ast@kernel.org>
Date: Thu, 7 Mar 2024 03:12:23 +0000 (-0800)
Subject: bpf: Allow kfuncs return 'void *'
X-Git-Url: http://xenbits.xensource.com/gitweb?a=commitdiff_plain;h=88d1d4a7eebea2836859246d91fe9d141789dfc3;p=people%2Faperard%2Flinux.git

bpf: Allow kfuncs return 'void *'

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

Acked-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/r/20240307031228.42896-2-alexei.starovoitov@gmail.com
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
---

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index ee86e4d7d5fcc..9c2a36b1373b9 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;