[PATCH bpf-next 4/4] bpf, btf: Enforce destructor kfunc type with CFI

[Sami Tolvanen <samitolvanen@google.com>]

Ensure that registered destructor kfuncs have the same type
as btf_dtor_kfunc_t to avoid a kernel panic on systems with
CONFIG_CFI_CLANG enabled.

Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
---
 kernel/bpf/btf.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 0aff814cb53a..2b0ebd46db4a 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -8856,6 +8856,13 @@ static int btf_check_dtor_kfuncs(struct btf *btf, const struct btf_id_dtor_kfunc
 		 */
 		if (!t || !btf_type_is_ptr(t))
 			return -EINVAL;
+
+		if (IS_ENABLED(CONFIG_CFI_CLANG)) {
+			/* Ensure the destructor kfunc type matches btf_dtor_kfunc_t */
+			t = btf_type_by_id(btf, t->type);
+			if (!btf_type_is_void(t))
+				return -EINVAL;
+		}
 	}
 	return 0;
 }
-- 
2.50.1.470.g6ba607880d-goog