linux-kernel - [PATCH 11/14] drm/amd/pm: Replace one-element array with flexible-array in struct phm_ppt_v1_mm_clock_voltage_dependency

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Date:   Wed, 7 Oct 2020 11:09:34 -0500
From:   "Gustavo A. R. Silva" <gustavoars@...nel.org>
To:     linux-kernel@...r.kernel.org
Cc:     linux-hardening@...r.kernel.org,
        Alex Deucher <alexander.deucher@....com>,
        Christian König <christian.koenig@....com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>, amd-gfx@...ts.freedesktop.org,
        dri-devel@...ts.freedesktop.org,
        "Gustavo A. R. Silva" <gustavoars@...nel.org>
Subject: [PATCH 11/14] drm/amd/pm: Replace one-element array with
 flexible-array in struct phm_ppt_v1_mm_clock_voltage_dependency_table

There is a regular need in the kernel to provide a way to declare having
a dynamically sized set of trailing elements in a structure. Kernel code
should always use “flexible array members”[1] for these cases. The older
style of one-element or zero-length arrays should no longer be used[2].

Refactor the code according to the use of a flexible-array member in
struct phm_ppt_v1_mm_clock_voltage_dependency_table, instead of a
one-element array, and use the struct_size() helper to calculate the
size for the allocation.

[1] https://en.wikipedia.org/wiki/Flexible_array_member
[2] https://www.kernel.org/doc/html/v5.9-rc1/process/deprecated.html#zero-length-and-one-element-arrays

Build-tested-by: kernel test robot <lkp@...el.com>
Link: https://lore.kernel.org/lkml/5f7d61e2.qiTVTyG2pVoG8bb0%25lkp@intel.com/
Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>
---
 drivers/gpu/drm/amd/pm/powerplay/hwmgr/hwmgr_ppt.h    |  2 +-
 .../amd/pm/powerplay/hwmgr/process_pptables_v1_0.c    | 11 ++++-------
 .../amd/pm/powerplay/hwmgr/vega10_processpptables.c   |  9 +++------
 3 files changed, 8 insertions(+), 14 deletions(-)

diff --git a/drivers/gpu/drm/amd/pm/powerplay/hwmgr/hwmgr_ppt.h b/drivers/gpu/drm/amd/pm/powerplay/hwmgr/hwmgr_ppt.h
index c167083b0872..923cc04e405a 100644
--- a/drivers/gpu/drm/amd/pm/powerplay/hwmgr/hwmgr_ppt.h
+++ b/drivers/gpu/drm/amd/pm/powerplay/hwmgr/hwmgr_ppt.h
@@ -71,7 +71,7 @@ typedef struct phm_ppt_v1_mm_clock_voltage_dependency_record phm_ppt_v1_mm_clock
 
 struct phm_ppt_v1_mm_clock_voltage_dependency_table {
 	uint32_t count;													/* Number of entries. */
-	phm_ppt_v1_mm_clock_voltage_dependency_record entries[1];		/* Dynamically allocate count entries. */
+	phm_ppt_v1_mm_clock_voltage_dependency_record entries[];		/* Dynamically allocate count entries. */
 };
 typedef struct phm_ppt_v1_mm_clock_voltage_dependency_table phm_ppt_v1_mm_clock_voltage_dependency_table;
 
diff --git a/drivers/gpu/drm/amd/pm/powerplay/hwmgr/process_pptables_v1_0.c b/drivers/gpu/drm/amd/pm/powerplay/hwmgr/process_pptables_v1_0.c
index 0725531fbfff..5d8016cd1986 100644
--- a/drivers/gpu/drm/amd/pm/powerplay/hwmgr/process_pptables_v1_0.c
+++ b/drivers/gpu/drm/amd/pm/powerplay/hwmgr/process_pptables_v1_0.c
@@ -678,19 +678,16 @@ static int get_mm_clock_voltage_table(
 		const ATOM_Tonga_MM_Dependency_Table * mm_dependency_table
 		)
 {
-	uint32_t table_size, i;
+	uint32_t i;
 	const ATOM_Tonga_MM_Dependency_Record *mm_dependency_record;
 	phm_ppt_v1_mm_clock_voltage_dependency_table *mm_table;
 	phm_ppt_v1_mm_clock_voltage_dependency_record *mm_table_record;
 
 	PP_ASSERT_WITH_CODE((0 != mm_dependency_table->ucNumEntries),
 		"Invalid PowerPlay Table!", return -1);
-	table_size = sizeof(uint32_t) +
-		sizeof(phm_ppt_v1_mm_clock_voltage_dependency_record)
-		* mm_dependency_table->ucNumEntries;
-	mm_table = kzalloc(table_size, GFP_KERNEL);
-
-	if (NULL == mm_table)
+	mm_table = kzalloc(struct_size(mm_table, entries, mm_dependency_table->ucNumEntries),
+			   GFP_KERNEL);
+	if (!mm_table)
 		return -ENOMEM;
 
 	mm_table->count = mm_dependency_table->ucNumEntries;
diff --git a/drivers/gpu/drm/amd/pm/powerplay/hwmgr/vega10_processpptables.c b/drivers/gpu/drm/amd/pm/powerplay/hwmgr/vega10_processpptables.c
index 787b23fa25e7..4f6a73a2cf28 100644
--- a/drivers/gpu/drm/amd/pm/powerplay/hwmgr/vega10_processpptables.c
+++ b/drivers/gpu/drm/amd/pm/powerplay/hwmgr/vega10_processpptables.c
@@ -344,18 +344,15 @@ static int get_mm_clock_voltage_table(
 		phm_ppt_v1_mm_clock_voltage_dependency_table **vega10_mm_table,
 		const ATOM_Vega10_MM_Dependency_Table *mm_dependency_table)
 {
-	uint32_t table_size, i;
+	uint32_t i;
 	const ATOM_Vega10_MM_Dependency_Record *mm_dependency_record;
 	phm_ppt_v1_mm_clock_voltage_dependency_table *mm_table;
 
 	PP_ASSERT_WITH_CODE((mm_dependency_table->ucNumEntries != 0),
 			"Invalid PowerPlay Table!", return -1);
 
-	table_size = sizeof(uint32_t) +
-			sizeof(phm_ppt_v1_mm_clock_voltage_dependency_record) *
-			mm_dependency_table->ucNumEntries;
-	mm_table = kzalloc(table_size, GFP_KERNEL);
-
+	mm_table = kzalloc(struct_size(mm_table, entries, mm_dependency_table->ucNumEntries),
+			   GFP_KERNEL);
 	if (!mm_table)
 		return -ENOMEM;
 
-- 
2.27.0