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Date:   Fri, 20 Aug 2021 11:27:57 -0400
From:   Alex Deucher <alexdeucher@...il.com>
To:     Kees Cook <keescook@...omium.org>
Cc:     Lijo Lazar <lijo.lazar@....com>,
        Christian König <christian.koenig@....com>,
        "Pan, Xinhui" <Xinhui.Pan@....com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Hawking Zhang <Hawking.Zhang@....com>,
        Feifei Xu <Feifei.Xu@....com>, Likun Gao <Likun.Gao@....com>,
        Jiawei Gu <Jiawei.Gu@....com>, Evan Quan <evan.quan@....com>,
        amd-gfx list <amd-gfx@...ts.freedesktop.org>,
        Maling list - DRI developers 
        <dri-devel@...ts.freedesktop.org>,
        Alex Deucher <alexander.deucher@....com>,
        Luben Tuikov <luben.tuikov@....com>,
        Andrey Grodzovsky <andrey.grodzovsky@....com>,
        Dennis Li <Dennis.Li@....com>,
        Sathishkumar S <sathishkumar.sundararaju@....com>,
        Jonathan Kim <jonathan.kim@....com>,
        Kevin Wang <kevin1.wang@....com>,
        David M Nieto <David.Nieto@....com>,
        Kenneth Feng <kenneth.feng@....com>,
        Lee Jones <lee.jones@...aro.org>,
        John Clements <John.Clements@....com>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-hardening@...r.kernel.org
Subject: Re: [PATCH] drm/amd/pm: And destination bounds checking to struct copy

On Thu, Aug 19, 2021 at 4:14 PM Kees Cook <keescook@...omium.org> wrote:
>
> In preparation for FORTIFY_SOURCE performing compile-time and run-time
> field bounds checking for memcpy(), memmove(), and memset(), avoid
> intentionally writing across neighboring fields.
>
> The "Board Parameters" members of the structs:
>         struct atom_smc_dpm_info_v4_5
>         struct atom_smc_dpm_info_v4_6
>         struct atom_smc_dpm_info_v4_7
>         struct atom_smc_dpm_info_v4_10
> are written to the corresponding members of the corresponding PPTable_t
> variables, but they lack destination size bounds checking, which means
> the compiler cannot verify at compile time that this is an intended and
> safe memcpy().
>
> Since the header files are effectively immutable[1] and a struct_group()
> cannot be used, nor a common struct referenced by both sides of the
> memcpy() arguments, add a new helper, memcpy_trailing(), to perform the
> bounds checking at compile time. Replace the open-coded memcpy()s with
> memcpy_trailing() which includes enough context for the bounds checking.
>
> "objdump -d" shows no object code changes.
>
> [1] https://lore.kernel.org/lkml/e56aad3c-a06f-da07-f491-a894a570d78f@amd.com
>
> Cc: Lijo Lazar <lijo.lazar@....com>
> Cc: "Christian König" <christian.koenig@....com>
> Cc: "Pan, Xinhui" <Xinhui.Pan@....com>
> Cc: David Airlie <airlied@...ux.ie>
> Cc: Daniel Vetter <daniel@...ll.ch>
> Cc: Hawking Zhang <Hawking.Zhang@....com>
> Cc: Feifei Xu <Feifei.Xu@....com>
> Cc: Likun Gao <Likun.Gao@....com>
> Cc: Jiawei Gu <Jiawei.Gu@....com>
> Cc: Evan Quan <evan.quan@....com>
> Cc: amd-gfx@...ts.freedesktop.org
> Cc: dri-devel@...ts.freedesktop.org
> Signed-off-by: Kees Cook <keescook@...omium.org>
> Link: https://lore.kernel.org/lkml/CADnq5_Npb8uYvd+R4UHgf-w8-cQj3JoODjviJR_Y9w9wqJ71mQ@mail.gmail.com
> ---
> Alex, I dropped your prior Acked-by, since the implementation is very
> different. If you're still happy with it, I can add it back. :)

This looks reasonable to me:
Acked-by: Alex Deucher <alexander.deucher@....com>

> ---
>  drivers/gpu/drm/amd/amdgpu/amdgpu.h           | 25 +++++++++++++++++++
>  .../gpu/drm/amd/pm/swsmu/smu11/arcturus_ppt.c |  6 ++---
>  .../gpu/drm/amd/pm/swsmu/smu11/navi10_ppt.c   |  8 +++---
>  .../drm/amd/pm/swsmu/smu13/aldebaran_ppt.c    |  5 ++--
>  4 files changed, 33 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu.h b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
> index 96e895d6be35..4605934a4fb7 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu.h
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
> @@ -1446,4 +1446,29 @@ static inline int amdgpu_in_reset(struct amdgpu_device *adev)
>  {
>         return atomic_read(&adev->in_gpu_reset);
>  }
> +
> +/**
> + * memcpy_trailing - Copy the end of one structure into the middle of another
> + *
> + * @dst: Pointer to destination struct
> + * @first_dst_member: The member name in @dst where the overwrite begins
> + * @last_dst_member: The member name in @dst where the overwrite ends after
> + * @src: Pointer to the source struct
> + * @first_src_member: The member name in @src where the copy begins
> + *
> + */
> +#define memcpy_trailing(dst, first_dst_member, last_dst_member,                   \
> +                       src, first_src_member)                             \
> +({                                                                        \
> +       size_t __src_offset = offsetof(typeof(*(src)), first_src_member);  \
> +       size_t __src_size = sizeof(*(src)) - __src_offset;                 \
> +       size_t __dst_offset = offsetof(typeof(*(dst)), first_dst_member);  \
> +       size_t __dst_size = offsetofend(typeof(*(dst)), last_dst_member) - \
> +                           __dst_offset;                                  \
> +       BUILD_BUG_ON(__src_size != __dst_size);                            \
> +       __builtin_memcpy((u8 *)(dst) + __dst_offset,                       \
> +                        (u8 *)(src) + __src_offset,                       \
> +                        __dst_size);                                      \
> +})
> +
>  #endif
> diff --git a/drivers/gpu/drm/amd/pm/swsmu/smu11/arcturus_ppt.c b/drivers/gpu/drm/amd/pm/swsmu/smu11/arcturus_ppt.c
> index 8ab58781ae13..1918e6232319 100644
> --- a/drivers/gpu/drm/amd/pm/swsmu/smu11/arcturus_ppt.c
> +++ b/drivers/gpu/drm/amd/pm/swsmu/smu11/arcturus_ppt.c
> @@ -465,10 +465,8 @@ static int arcturus_append_powerplay_table(struct smu_context *smu)
>
>         if ((smc_dpm_table->table_header.format_revision == 4) &&
>             (smc_dpm_table->table_header.content_revision == 6))
> -               memcpy(&smc_pptable->MaxVoltageStepGfx,
> -                      &smc_dpm_table->maxvoltagestepgfx,
> -                      sizeof(*smc_dpm_table) - offsetof(struct atom_smc_dpm_info_v4_6, maxvoltagestepgfx));
> -
> +               memcpy_trailing(smc_pptable, MaxVoltageStepGfx, BoardReserved,
> +                               smc_dpm_table, maxvoltagestepgfx);
>         return 0;
>  }
>
> diff --git a/drivers/gpu/drm/amd/pm/swsmu/smu11/navi10_ppt.c b/drivers/gpu/drm/amd/pm/swsmu/smu11/navi10_ppt.c
> index 2e5d3669652b..b738042e064d 100644
> --- a/drivers/gpu/drm/amd/pm/swsmu/smu11/navi10_ppt.c
> +++ b/drivers/gpu/drm/amd/pm/swsmu/smu11/navi10_ppt.c
> @@ -431,16 +431,16 @@ static int navi10_append_powerplay_table(struct smu_context *smu)
>
>         switch (smc_dpm_table->table_header.content_revision) {
>         case 5: /* nv10 and nv14 */
> -               memcpy(smc_pptable->I2cControllers, smc_dpm_table->I2cControllers,
> -                       sizeof(*smc_dpm_table) - sizeof(smc_dpm_table->table_header));
> +               memcpy_trailing(smc_pptable, I2cControllers, BoardReserved,
> +                               smc_dpm_table, I2cControllers);
>                 break;
>         case 7: /* nv12 */
>                 ret = amdgpu_atombios_get_data_table(adev, index, NULL, NULL, NULL,
>                                               (uint8_t **)&smc_dpm_table_v4_7);
>                 if (ret)
>                         return ret;
> -               memcpy(smc_pptable->I2cControllers, smc_dpm_table_v4_7->I2cControllers,
> -                       sizeof(*smc_dpm_table_v4_7) - sizeof(smc_dpm_table_v4_7->table_header));
> +               memcpy_trailing(smc_pptable, I2cControllers, BoardReserved,
> +                               smc_dpm_table_v4_7, I2cControllers);
>                 break;
>         default:
>                 dev_err(smu->adev->dev, "smc_dpm_info with unsupported content revision %d!\n",
> diff --git a/drivers/gpu/drm/amd/pm/swsmu/smu13/aldebaran_ppt.c b/drivers/gpu/drm/amd/pm/swsmu/smu13/aldebaran_ppt.c
> index c8eefacfdd37..a6fd7ee314a9 100644
> --- a/drivers/gpu/drm/amd/pm/swsmu/smu13/aldebaran_ppt.c
> +++ b/drivers/gpu/drm/amd/pm/swsmu/smu13/aldebaran_ppt.c
> @@ -409,9 +409,8 @@ static int aldebaran_append_powerplay_table(struct smu_context *smu)
>
>         if ((smc_dpm_table->table_header.format_revision == 4) &&
>             (smc_dpm_table->table_header.content_revision == 10))
> -               memcpy(&smc_pptable->GfxMaxCurrent,
> -                      &smc_dpm_table->GfxMaxCurrent,
> -                      sizeof(*smc_dpm_table) - offsetof(struct atom_smc_dpm_info_v4_10, GfxMaxCurrent));
> +               memcpy_trailing(smc_pptable, GfxMaxCurrent, reserved,
> +                               smc_dpm_table, GfxMaxCurrent);
>         return 0;
>  }
>
> --
> 2.30.2
>

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