linux-kernel - Re: [PATCH] drm/nouveau/secboot/acr: Remove VLA usage

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Message-ID: <CAGXu5jJPmeJTLiJrPqeQWhcRwFh3GgpL8RfWvHoK+Kvd=mybFg@mail.gmail.com>
Date:   Tue, 19 Jun 2018 21:45:41 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Alexandre Courbot <acourbot@...dia.com>,
        Ben Skeggs <bskeggs@...hat.com>
Cc:     Maling list - DRI developers <dri-devel@...ts.freedesktop.org>,
        LKML <linux-kernel@...r.kernel.org>,
        nouveau <nouveau@...ts.freedesktop.org>
Subject: Re: [PATCH] drm/nouveau/secboot/acr: Remove VLA usage

On Thu, May 24, 2018 at 10:24 AM, Kees Cook <keescook@...omium.org> wrote:
> In the quest to remove all stack VLA usage from the kernel[1], this
> allocates the working buffers before starting the writing so it won't
> abort in the middle. This needs an initial walk of the lists to figure
> out how large the buffer should be.
>
> [1] https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@mail.gmail.com
>
> Signed-off-by: Kees Cook <keescook@...omium.org>

Friendly ping. Who is best to take this patch?

Thanks!

-Kees

> ---
>  .../nouveau/nvkm/subdev/secboot/acr_r352.c    | 25 ++++++++++++++++---
>  .../nouveau/nvkm/subdev/secboot/acr_r367.c    | 16 +++++++++++-
>  2 files changed, 37 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/nouveau/nvkm/subdev/secboot/acr_r352.c b/drivers/gpu/drm/nouveau/nvkm/subdev/secboot/acr_r352.c
> index a721354249ce..d02e183717dc 100644
> --- a/drivers/gpu/drm/nouveau/nvkm/subdev/secboot/acr_r352.c
> +++ b/drivers/gpu/drm/nouveau/nvkm/subdev/secboot/acr_r352.c
> @@ -414,6 +414,20 @@ acr_r352_ls_write_wpr(struct acr_r352 *acr, struct list_head *imgs,
>  {
>         struct ls_ucode_img *_img;
>         u32 pos = 0;
> +       u32 max_desc_size = 0;
> +       u8 *gdesc;
> +
> +       /* Figure out how large we need gdesc to be. */
> +       list_for_each_entry(_img, imgs, node) {
> +               const struct acr_r352_ls_func *ls_func =
> +                                           acr->func->ls_func[_img->falcon_id];
> +
> +               max_desc_size = max(max_desc_size, ls_func->bl_desc_size);
> +       }
> +
> +       gdesc = kmalloc(max_desc_size, GFP_KERNEL);
> +       if (!gdesc)
> +               return -ENOMEM;
>
>         nvkm_kmap(wpr_blob);
>
> @@ -421,7 +435,6 @@ acr_r352_ls_write_wpr(struct acr_r352 *acr, struct list_head *imgs,
>                 struct ls_ucode_img_r352 *img = ls_ucode_img_r352(_img);
>                 const struct acr_r352_ls_func *ls_func =
>                                             acr->func->ls_func[_img->falcon_id];
> -               u8 gdesc[ls_func->bl_desc_size];
>
>                 nvkm_gpuobj_memcpy_to(wpr_blob, pos, &img->wpr_header,
>                                       sizeof(img->wpr_header));
> @@ -447,6 +460,8 @@ acr_r352_ls_write_wpr(struct acr_r352 *acr, struct list_head *imgs,
>
>         nvkm_done(wpr_blob);
>
> +       kfree(gdesc);
> +
>         return 0;
>  }
>
> @@ -771,7 +786,11 @@ acr_r352_load(struct nvkm_acr *_acr, struct nvkm_falcon *falcon,
>         struct fw_bl_desc *hsbl_desc;
>         void *bl, *blob_data, *hsbl_code, *hsbl_data;
>         u32 code_size;
> -       u8 bl_desc[bl_desc_size];
> +       u8 *bl_desc;
> +
> +       bl_desc = kzalloc(bl_desc_size, GFP_KERNEL);
> +       if (!bl_desc)
> +               return -ENOMEM;
>
>         /* Find the bootloader descriptor for our blob and copy it */
>         if (blob == acr->load_blob) {
> @@ -802,7 +821,6 @@ acr_r352_load(struct nvkm_acr *_acr, struct nvkm_falcon *falcon,
>                               code_size, hsbl_desc->start_tag, 0, false);
>
>         /* Generate the BL header */
> -       memset(bl_desc, 0, bl_desc_size);
>         acr->func->generate_hs_bl_desc(load_hdr, bl_desc, offset);
>
>         /*
> @@ -811,6 +829,7 @@ acr_r352_load(struct nvkm_acr *_acr, struct nvkm_falcon *falcon,
>         nvkm_falcon_load_dmem(falcon, bl_desc, hsbl_desc->dmem_load_off,
>                               bl_desc_size, 0);
>
> +       kfree(bl_desc);
>         return hsbl_desc->start_tag << 8;
>  }
>
> diff --git a/drivers/gpu/drm/nouveau/nvkm/subdev/secboot/acr_r367.c b/drivers/gpu/drm/nouveau/nvkm/subdev/secboot/acr_r367.c
> index 866877b88797..978ad0790367 100644
> --- a/drivers/gpu/drm/nouveau/nvkm/subdev/secboot/acr_r367.c
> +++ b/drivers/gpu/drm/nouveau/nvkm/subdev/secboot/acr_r367.c
> @@ -265,6 +265,19 @@ acr_r367_ls_write_wpr(struct acr_r352 *acr, struct list_head *imgs,
>  {
>         struct ls_ucode_img *_img;
>         u32 pos = 0;
> +       u32 max_desc_size = 0;
> +       u8 *gdesc;
> +
> +       list_for_each_entry(_img, imgs, node) {
> +               const struct acr_r352_ls_func *ls_func =
> +                                           acr->func->ls_func[_img->falcon_id];
> +
> +               max_desc_size = max(max_desc_size, ls_func->bl_desc_size);
> +       }
> +
> +       gdesc = kmalloc(max_desc_size, GFP_KERNEL);
> +       if (!gdesc)
> +               return -ENOMEM;
>
>         nvkm_kmap(wpr_blob);
>
> @@ -272,7 +285,6 @@ acr_r367_ls_write_wpr(struct acr_r352 *acr, struct list_head *imgs,
>                 struct ls_ucode_img_r367 *img = ls_ucode_img_r367(_img);
>                 const struct acr_r352_ls_func *ls_func =
>                                             acr->func->ls_func[_img->falcon_id];
> -               u8 gdesc[ls_func->bl_desc_size];
>
>                 nvkm_gpuobj_memcpy_to(wpr_blob, pos, &img->wpr_header,
>                                       sizeof(img->wpr_header));
> @@ -298,6 +310,8 @@ acr_r367_ls_write_wpr(struct acr_r352 *acr, struct list_head *imgs,
>
>         nvkm_done(wpr_blob);
>
> +       kfree(gdesc);
> +
>         return 0;
>  }
>
> --
> 2.17.0
>
>
> --
> Kees Cook
> Pixel Security



-- 
Kees Cook
Pixel Security