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bpf: check bpf_dummy_struct_ops program params for test runs 

When doing BPF_PROG_TEST_RUN for bpf_dummy_struct_ops programs,
reject execution when NULL is passed for non-nullable params.
For programs with non-nullable params verifier assumes that
such params are never NULL and thus might optimize out NULL checks.

Suggested-by: Kui-Feng Lee <sinquersw@gmail.com>
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20240424012821.595216-5-eddyz87@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Eduard Zingerman 2024-04-23 18:28:20 -07:00 committed by Alexei Starovoitov
parent f612210d45
commit 980ca8ceea
1 changed files with 50 additions and 1 deletions
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51
net/bpf/bpf_dummy_struct_ops.c
View File

@ -79,6 +79,51 @@ static int dummy_ops_call_op(void *image, struct bpf_dummy_ops_test_args *args)
args->args[3], args->args[4]);
}
static const struct bpf_ctx_arg_aux *find_ctx_arg_info(struct bpf_prog_aux *aux, int offset)
{
int i;
for (i = 0; i < aux->ctx_arg_info_size; i++)
if (aux->ctx_arg_info[i].offset == offset)
return &aux->ctx_arg_info[i];
return NULL;
}
/* There is only one check at the moment:
* - zero should not be passed for pointer parameters not marked as nullable.
*/
static int check_test_run_args(struct bpf_prog *prog, struct bpf_dummy_ops_test_args *args)
{
const struct btf_type *func_proto = prog->aux->attach_func_proto;
for (u32 arg_no = 0; arg_no < btf_type_vlen(func_proto) ; ++arg_no) {
const struct btf_param *param = &btf_params(func_proto)[arg_no];
const struct bpf_ctx_arg_aux *info;
const struct btf_type *t;
int offset;
if (args->args[arg_no] != 0)
continue;
/* Program is validated already, so there is no need
* to check if t is NULL.
*/
t = btf_type_skip_modifiers(bpf_dummy_ops_btf, param->type, NULL);
if (!btf_type_is_ptr(t))
continue;
offset = btf_ctx_arg_offset(bpf_dummy_ops_btf, func_proto, arg_no);
info = find_ctx_arg_info(prog->aux, offset);
if (info && (info->reg_type & PTR_MAYBE_NULL))
continue;
return -EINVAL;
}
return 0;
}
extern const struct bpf_link_ops bpf_struct_ops_link_lops;
int bpf_struct_ops_test_run(struct bpf_prog *prog, const union bpf_attr *kattr,
@ -87,7 +132,7 @@ int bpf_struct_ops_test_run(struct bpf_prog *prog, const union bpf_attr *kattr,
const struct bpf_struct_ops *st_ops = &bpf_bpf_dummy_ops;
const struct btf_type *func_proto;
struct bpf_dummy_ops_test_args *args;
struct bpf_tramp_links *tlinks;
struct bpf_tramp_links *tlinks = NULL;
struct bpf_tramp_link *link = NULL;
void *image = NULL;
unsigned int op_idx;
@ -109,6 +154,10 @@ int bpf_struct_ops_test_run(struct bpf_prog *prog, const union bpf_attr *kattr,
if (IS_ERR(args))
return PTR_ERR(args);
err = check_test_run_args(prog, args);
if (err)
goto out;
tlinks = kcalloc(BPF_TRAMP_MAX, sizeof(*tlinks), GFP_KERNEL);
if (!tlinks) {
err = -ENOMEM;