[PATCH] drm/amd/pm: And destination bounds checking to struct copy

[Kees Cook]

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 at amd.com>
Cc: "Christian König" <christian.koenig at amd.com>
Cc: "Pan, Xinhui" <Xinhui.Pan at amd.com>
Cc: David Airlie <airlied at linux.ie>
Cc: Daniel Vetter <daniel at ffwll.ch>
Cc: Hawking Zhang <Hawking.Zhang at amd.com>
Cc: Feifei Xu <Feifei.Xu at amd.com>
Cc: Likun Gao <Likun.Gao at amd.com>
Cc: Jiawei Gu <Jiawei.Gu at amd.com>
Cc: Evan Quan <evan.quan at amd.com>
Cc: amd-gfx at lists.freedesktop.org
Cc: dri-devel at lists.freedesktop.org
Signed-off-by: Kees Cook <keescook at chromium.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. :)
---
 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