On Fri, Sep 6, 2024 at 6:56 AM Daniel Borkmann <daniel@xxxxxxxxxxxxx> wrote:
>
> When checking malformed helper function signatures, also take other argument
> types into account aside from just ARG_PTR_TO_UNINIT_MEM.
>
> This concerns (formerly) ARG_PTR_TO_{INT,LONG} given uninitialized memory can
> be passed there, too.
>
> The func proto sanity check goes back to commit 435faee1aae9 ("bpf, verifier:
> add ARG_PTR_TO_RAW_STACK type"), and its purpose was to detect wrong func protos
> which had more than just one MEM_UNINIT-tagged type as arguments.
>
> The reason more than one is currently not supported is as we mark stack slots with
> STACK_MISC in check_helper_call() in case of raw mode based on meta.access_size to
> allow uninitialized stack memory to be passed to helpers when they just write into
> the buffer.
>
> Probing for base type as well as MEM_UNINIT tagging ensures that other types do not
> get missed (as it used to be the case for ARG_PTR_TO_{INT,LONG}).
>
> Fixes: 57c3bb725a3d ("bpf: Introduce ARG_PTR_TO_{INT,LONG} arg types")
> Reported-by: Shung-Hsi Yu <shung-hsi.yu@xxxxxxxx>
> Signed-off-by: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
> ---
> v1 -> v2:
> - new patch (Shung-Hsi)
> v2 -> v3:
> - base_type(type) was needed also
>
> kernel/bpf/verifier.c | 16 +++++++++++-----
> 1 file changed, 11 insertions(+), 5 deletions(-)
>
LGTM (though I like straight unwrapped lines ;))
Acked-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> index 3a0801933a79..a1bbe4b401af 100644
> --- a/kernel/bpf/verifier.c
> +++ b/kernel/bpf/verifier.c
> @@ -8291,6 +8291,12 @@ static bool arg_type_is_mem_size(enum bpf_arg_type type)
> type == ARG_CONST_SIZE_OR_ZERO;
> }
>
> +static bool arg_type_is_raw_mem(enum bpf_arg_type type)
> +{
> + return base_type(type) == ARG_PTR_TO_MEM &&
> + type & MEM_UNINIT;
> +}
> +
> static bool arg_type_is_release(enum bpf_arg_type type)
> {
> return type & OBJ_RELEASE;
> @@ -9343,15 +9349,15 @@ static bool check_raw_mode_ok(const struct bpf_func_proto *fn)
> {
> int count = 0;
>
> - if (fn->arg1_type == ARG_PTR_TO_UNINIT_MEM)
> + if (arg_type_is_raw_mem(fn->arg1_type))
> count++;
> - if (fn->arg2_type == ARG_PTR_TO_UNINIT_MEM)
> + if (arg_type_is_raw_mem(fn->arg2_type))
> count++;
> - if (fn->arg3_type == ARG_PTR_TO_UNINIT_MEM)
> + if (arg_type_is_raw_mem(fn->arg3_type))
> count++;
> - if (fn->arg4_type == ARG_PTR_TO_UNINIT_MEM)
> + if (arg_type_is_raw_mem(fn->arg4_type))
> count++;
> - if (fn->arg5_type == ARG_PTR_TO_UNINIT_MEM)
> + if (arg_type_is_raw_mem(fn->arg5_type))
> count++;
>
> /* We only support one arg being in raw mode at the moment,
> --
> 2.43.0
>
