bpf: Check cfi_stubs before registering a struct_ops type.

Recently, st_ops->cfi_stubs was introduced. However, the upcoming new
struct_ops support (e.g. sched_ext) is not aware of this and does not
provide its own cfi_stubs. The kernel ends up NULL dereferencing the
st_ops->cfi_stubs.

Considering struct_ops supports kernel module now, this NULL check
is necessary. This patch is to reject struct_ops registration
that does not provide a cfi_stubs.

Signed-off-by: Kui-Feng Lee <thinker.li@gmail.com>
Link: https://lore.kernel.org/r/20240222021105.1180475-2-thinker.li@gmail.com
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>

diff --git a/kernel/bpf/bpf_struct_ops.c b/kernel/bpf/bpf_struct_ops.c
index 0d7be97a2411c8e8e9379978767cf3a2ff99a80a..a6019087b467c2612ee20f8205a3268cc51beb22 100644 (file)
--- a/kernel/bpf/bpf_struct_ops.c
+++ b/kernel/bpf/bpf_struct_ops.c
@@ -302,6 +302,11 @@ int bpf_struct_ops_desc_init(struct bpf_struct_ops_desc *st_ops_desc,
        }
        sprintf(value_name, "%s%s", VALUE_PREFIX, st_ops->name);
 
+       if (!st_ops->cfi_stubs) {
+               pr_warn("struct_ops for %s has no cfi_stubs\n", st_ops->name);
+               return -EINVAL;
+       }
+
        type_id = btf_find_by_name_kind(btf, st_ops->name,
                                        BTF_KIND_STRUCT);
        if (type_id < 0) {