linux-hardening - [PATCH 12/14] drm/amd/pm: Replace one-element array with flexible-array in struct phm_ppt_v1_voltage_lookup

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Date:   Wed, 7 Oct 2020 11:10:16 -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 12/14] drm/amd/pm: Replace one-element array with
 flexible-array in struct phm_ppt_v1_voltage_lookup_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_voltage_lookup_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/5f7d61df.jWrFfnjxGbjSkPOp%25lkp@intel.com/
Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>
---
 drivers/gpu/drm/amd/pm/powerplay/hwmgr/hwmgr_ppt.h     |  2 +-
 .../drm/amd/pm/powerplay/hwmgr/process_pptables_v1_0.c | 10 +++-------
 .../amd/pm/powerplay/hwmgr/vega10_processpptables.c    | 10 +++-------
 3 files changed, 7 insertions(+), 15 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 923cc04e405a..e11298cdeb30 100644
--- a/drivers/gpu/drm/amd/pm/powerplay/hwmgr/hwmgr_ppt.h
+++ b/drivers/gpu/drm/amd/pm/powerplay/hwmgr/hwmgr_ppt.h
@@ -86,7 +86,7 @@ typedef struct phm_ppt_v1_voltage_lookup_record phm_ppt_v1_voltage_lookup_record
 
 struct phm_ppt_v1_voltage_lookup_table {
 	uint32_t count;
-	phm_ppt_v1_voltage_lookup_record entries[1];    /* Dynamically allocate count entries. */
+	phm_ppt_v1_voltage_lookup_record entries[];    /* Dynamically allocate count entries. */
 };
 typedef struct phm_ppt_v1_voltage_lookup_table phm_ppt_v1_voltage_lookup_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 5d8016cd1986..426655b9c678 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
@@ -157,7 +157,7 @@ static int get_vddc_lookup_table(
 		uint32_t max_levels
 		)
 {
-	uint32_t table_size, i;
+	uint32_t i;
 	phm_ppt_v1_voltage_lookup_table *table;
 	phm_ppt_v1_voltage_lookup_record *record;
 	ATOM_Tonga_Voltage_Lookup_Record *atom_record;
@@ -165,12 +165,8 @@ static int get_vddc_lookup_table(
 	PP_ASSERT_WITH_CODE((0 != vddc_lookup_pp_tables->ucNumEntries),
 		"Invalid CAC Leakage PowerPlay Table!", return 1);
 
-	table_size = sizeof(uint32_t) +
-		sizeof(phm_ppt_v1_voltage_lookup_record) * max_levels;
-
-	table = kzalloc(table_size, GFP_KERNEL);
-
-	if (NULL == table)
+	table = kzalloc(struct_size(table, entries, max_levels), GFP_KERNEL);
+	if (!table)
 		return -ENOMEM;
 
 	table->count = vddc_lookup_pp_tables->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 4f6a73a2cf28..3d7f915381c8 100644
--- a/drivers/gpu/drm/amd/pm/powerplay/hwmgr/vega10_processpptables.c
+++ b/drivers/gpu/drm/amd/pm/powerplay/hwmgr/vega10_processpptables.c
@@ -1040,18 +1040,14 @@ static int get_vddc_lookup_table(
 		const ATOM_Vega10_Voltage_Lookup_Table *vddc_lookup_pp_tables,
 		uint32_t max_levels)
 {
-	uint32_t table_size, i;
+	uint32_t i;
 	phm_ppt_v1_voltage_lookup_table *table;
 
 	PP_ASSERT_WITH_CODE((vddc_lookup_pp_tables->ucNumEntries != 0),
 			"Invalid SOC_VDDD Lookup Table!", return 1);
 
-	table_size = sizeof(uint32_t) +
-			sizeof(phm_ppt_v1_voltage_lookup_record) * max_levels;
-
-	table = kzalloc(table_size, GFP_KERNEL);
-
-	if (table == NULL)
+	table = kzalloc(struct_size(table, entries, max_levels), GFP_KERNEL);
+	if (!table)
 		return -ENOMEM;
 
 	table->count = vddc_lookup_pp_tables->ucNumEntries;
-- 
2.27.0