netdev - [PATCH bpf-next] bpf: return -EOPNOTSUPP when attaching to non-kernel BTF

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Date:   Fri, 4 Dec 2020 19:09:51 -0800
From:   Andrii Nakryiko <andrii@...nel.org>
To:     <bpf@...r.kernel.org>, <netdev@...r.kernel.org>, <ast@...com>,
        <daniel@...earbox.net>
CC:     <andrii@...nel.org>, <kernel-team@...com>,
        Alexei Starovoitov <ast@...nel.org>
Subject: [PATCH bpf-next] bpf: return -EOPNOTSUPP when attaching to non-kernel BTF

Return -EOPNOTSUPP if tracing BPF program is attempted to be attached with
specified attach_btf_obj_fd pointing to non-kernel (neither vmlinux nor
module) BTF object. This scenario might be supported in the future and isn't
outright invalid, so -EINVAL isn't the most appropriate error code.

Suggested-by: Alexei Starovoitov <ast@...nel.org>
Signed-off-by: Andrii Nakryiko <andrii@...nel.org>
---
 kernel/bpf/syscall.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 0cd3cc2af9c1..7e2bf671c6db 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -2121,8 +2121,11 @@ static int bpf_prog_load(union bpf_attr *attr, union bpf_attr __user *uattr)
 			if (IS_ERR(attach_btf))
 				return -EINVAL;
 			if (!btf_is_kernel(attach_btf)) {
+				/* attaching through specifying bpf_prog's BTF
+				 * objects directly might be supported eventually
+				 */
 				btf_put(attach_btf);
-				return -EINVAL;
+				return -EOPNOTSUPP;
 			}
 		}
 	} else if (attr->attach_btf_id) {
-- 
2.24.1