On Thu, Apr 28, 2022 at 2:12 PM Joanne Koong <joannelkoong@xxxxxxxxx> wrote:
>
> Instead of having uninitialized versions of arguments as separate
> bpf_arg_types (eg ARG_PTR_TO_UNINIT_MEM as the uninitialized version
> of ARG_PTR_TO_MEM), we can instead use MEM_UNINIT as a bpf_type_flag
> modifier to denote that the argument is uninitialized.
>
> Doing so cleans up some of the logic in the verifier. We no longer
> need to do two checks against an argument type (eg "if
> (base_type(arg_type) == ARG_PTR_TO_MEM || base_type(arg_type) ==
> ARG_PTR_TO_UNINIT_MEM)"), since uninitialized and initialized
> versions of the same argument type will now share the same base type.
>
> In the near future, MEM_UNINIT will be used by dynptr helper functions
> as well.
>
> Signed-off-by: Joanne Koong <joannelkoong@xxxxxxxxx>
> ---
LGTM, see minor suggestion below
Acked-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
> include/linux/bpf.h | 17 +++++++++--------
> kernel/bpf/helpers.c | 4 ++--
> kernel/bpf/verifier.c | 26 ++++++++------------------
> 3 files changed, 19 insertions(+), 28 deletions(-)
>
[...]
> @@ -6189,9 +6179,9 @@ static bool check_raw_mode_ok(const struct bpf_func_proto *fn)
> static bool check_args_pair_invalid(enum bpf_arg_type arg_curr,
> enum bpf_arg_type arg_next)
> {
> - return (arg_type_is_mem_ptr(arg_curr) &&
> + return (base_type(arg_curr) == ARG_PTR_TO_MEM &&
> !arg_type_is_mem_size(arg_next)) ||
> - (!arg_type_is_mem_ptr(arg_curr) &&
> + (base_type(arg_curr) != ARG_PTR_TO_MEM &&
> arg_type_is_mem_size(arg_next));
trying to parse this check I realized that it can be written as !=
(basically it's a XOR, both conditions are either true or both are
false)
return (base_type(arg_curr) == ARG_PTR_TO_MEM) !=
arg_type_is_mem_size(arg_next);
> }
>
> @@ -6203,7 +6193,7 @@ static bool check_arg_pair_ok(const struct bpf_func_proto *fn)
> * helper function specification.
> */
> if (arg_type_is_mem_size(fn->arg1_type) ||
> - arg_type_is_mem_ptr(fn->arg5_type) ||
> + base_type(fn->arg5_type) == ARG_PTR_TO_MEM ||
> check_args_pair_invalid(fn->arg1_type, fn->arg2_type) ||
> check_args_pair_invalid(fn->arg2_type, fn->arg3_type) ||
> check_args_pair_invalid(fn->arg3_type, fn->arg4_type) ||
> --
> 2.30.2
>
