On 12/13/24 3:29 PM, Amery Hung wrote:
@@ -15993,13 +16001,15 @@ static int check_return_code(struct bpf_verifier_env *env, int regno, const char
const char *exit_ctx = "At program exit";
struct tnum enforce_attach_type_range = tnum_unknown;
const struct bpf_prog *prog = env->prog;
- struct bpf_reg_state *reg;
+ struct bpf_reg_state *reg = reg_state(env, regno);
struct bpf_retval_range range = retval_range(0, 1);
enum bpf_prog_type prog_type = resolve_prog_type(env->prog);
int err;
struct bpf_func_state *frame = env->cur_state->frame[0];
const bool is_subprog = frame->subprogno;
bool return_32bit = false;
+ struct btf *btf = bpf_prog_get_target_btf(prog);
+ const struct btf_type *ret_type = NULL;
/* LSM and struct_ops func-ptr's return type could be "void" */
if (!is_subprog || frame->in_exception_callback_fn) {
@@ -16008,10 +16018,31 @@ static int check_return_code(struct bpf_verifier_env *env, int regno, const char
if (prog->expected_attach_type == BPF_LSM_CGROUP)
/* See below, can be 0 or 0-1 depending on hook. */
break;
- fallthrough;
+ if (!prog->aux->attach_func_proto->type)
+ return 0;
+ break;
case BPF_PROG_TYPE_STRUCT_OPS:
if (!prog->aux->attach_func_proto->type)
return 0;
+
+ if (frame->in_exception_callback_fn)
+ break;
+
+ /* Allow a struct_ops program to return a referenced kptr if it
+ * matches the operator's return type and is in its unmodified
+ * form. A scalar zero (i.e., a null pointer) is also allowed.
+ */
+ ret_type = btf_type_by_id(btf, prog->aux->attach_func_proto->type);
+ if (btf_type_is_ptr(ret_type) && reg->type & PTR_TO_BTF_ID &&
The "reg->type & PTR_TO_BTF_ID" does not look right. It should be
"base_type(reg->type) == PTR_TO_BTF_ID".
+ reg->ref_obj_id) {
+ if (reg->btf_id != ret_type->type) {
reg->btf could be a bpf prog's btf (i.e. prog->aux->btf) instead of the kernel
btf, so only comparing btf_id here is not very correct.
One way could be to first compare the reg->btf == prog->aux->attach_btf.
prog->aux->attach_btf here must be a kernel btf.
Another way is, btf_type_resolve_ptr() should be a better helper than
btf_type_by_id() here. It only returns non NULL if the type is a pointer and
also skips the modifiers like "const" before returning. Then it can directly
compare the "struct btf_type *" returned by
'btf_type_resolve_ptr(prog->aux->attach_btf, prog->aux->attach_func_proto->type,
NULL)' and 'btf_type_resolve_ptr(reg->btf, reg->btf_id, NULL)'
May as well enforce the pointer returned by an "ops" must be a struct (i.e.
__btf_type_is_struct(t) == true). This enforcement can be done in
bpf_struct_ops_desc_init().
+ verbose(env, "Return kptr type, struct %s, doesn't match function prototype, struct %s\n",
+ btf_type_name(reg->btf, reg->btf_id),
+ btf_type_name(btf, ret_type->type));
+ return -EINVAL;
+ }
+ return __check_ptr_off_reg(env, reg, regno, false);
+ }
break;
default:
break;
@@ -16033,8 +16064,6 @@ static int check_return_code(struct bpf_verifier_env *env, int regno, const char
return -EACCES;
}
- reg = cur_regs(env) + regno;
-
if (frame->in_async_callback_fn) {
/* enforce return zero from async callbacks like timer */
exit_ctx = "At async callback return";
@@ -16133,6 +16162,11 @@ static int check_return_code(struct bpf_verifier_env *env, int regno, const char
case BPF_PROG_TYPE_NETFILTER:
range = retval_range(NF_DROP, NF_ACCEPT);
break;
+ case BPF_PROG_TYPE_STRUCT_OPS:
+ if (!ret_type || !btf_type_is_ptr(ret_type))
+ return 0;
+ range = retval_range(0, 0);
+ break;
case BPF_PROG_TYPE_EXT:
/* freplace program can return anything as its return value
* depends on the to-be-replaced kernel func or bpf program.
