diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index e64035683795..7d8ddb1bee00 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -17089,6 +17089,15 @@ static int check_ld_imm(struct bpf_verifier_env *env, struct bpf_insn *insn)
 			verbose(env, "callback function not static\n");
 			return -EINVAL;
 		}
+		/*
+		 * When env->subprog_cnt == 1 this instruction won't be rewritten
+		 * to hold a real function address. Assume that no usable program
+		 * combines e.g. main and timer callback and just reject here.
+		 */
+		if (subprogno == 0) {
+			verbose(env, "callback function cannot be the main program\n");
+			return -EINVAL;
+		}
 
 		dst_reg->type = PTR_TO_FUNC;
 		dst_reg->subprogno = subprogno;