linux-kernel - [PATCH 13/14] drm/amd/pm: Replace one-element array with flexible-array in struct phm_ppt_v1_pcie

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Date:   Wed, 7 Oct 2020 11:10:44 -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 13/14] drm/amd/pm: Replace one-element array with
 flexible-array in struct phm_ppt_v1_pcie_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_pcie_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/5f7db0bc.7Xivn4K83f7XW0ug%25lkp@intel.com/
Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>
---
 .../drm/amd/pm/powerplay/hwmgr/hwmgr_ppt.h    |  2 +-
 .../powerplay/hwmgr/process_pptables_v1_0.c   | 22 ++++++++-----------
 .../powerplay/hwmgr/vega10_processpptables.c  | 10 +++------
 3 files changed, 13 insertions(+), 21 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 e11298cdeb30..729615aff126 100644
--- a/drivers/gpu/drm/amd/pm/powerplay/hwmgr/hwmgr_ppt.h
+++ b/drivers/gpu/drm/amd/pm/powerplay/hwmgr/hwmgr_ppt.h
@@ -103,7 +103,7 @@ typedef struct phm_ppt_v1_pcie_record phm_ppt_v1_pcie_record;
 
 struct phm_ppt_v1_pcie_table {
 	uint32_t count;                                            /* Number of entries. */
-	phm_ppt_v1_pcie_record entries[1];                         /* Dynamically allocate count entries. */
+	phm_ppt_v1_pcie_record entries[];			   /* Dynamically allocate count entries. */
 };
 typedef struct phm_ppt_v1_pcie_table phm_ppt_v1_pcie_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 426655b9c678..4fa58614e26a 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
@@ -478,7 +478,7 @@ static int get_pcie_table(
 		PPTable_Generic_SubTable_Header const *ptable
 		)
 {
-	uint32_t table_size, i, pcie_count;
+	uint32_t i, pcie_count;
 	phm_ppt_v1_pcie_table *pcie_table;
 	struct phm_ppt_v1_information *pp_table_information =
 		(struct phm_ppt_v1_information *)(hwmgr->pptable);
@@ -491,12 +491,10 @@ static int get_pcie_table(
 		PP_ASSERT_WITH_CODE((atom_pcie_table->ucNumEntries != 0),
 			"Invalid PowerPlay Table!", return -1);
 
-		table_size = sizeof(uint32_t) +
-			sizeof(phm_ppt_v1_pcie_record) * atom_pcie_table->ucNumEntries;
-
-		pcie_table = kzalloc(table_size, GFP_KERNEL);
-
-		if (pcie_table == NULL)
+		pcie_table = kzalloc(struct_size(pcie_table, entries,
+						 atom_pcie_table->ucNumEntries),
+				     GFP_KERNEL);
+		if (!pcie_table)
 			return -ENOMEM;
 
 		/*
@@ -530,12 +528,10 @@ static int get_pcie_table(
 		PP_ASSERT_WITH_CODE((atom_pcie_table->ucNumEntries != 0),
 			"Invalid PowerPlay Table!", return -1);
 
-		table_size = sizeof(uint32_t) +
-			sizeof(phm_ppt_v1_pcie_record) * atom_pcie_table->ucNumEntries;
-
-		pcie_table = kzalloc(table_size, GFP_KERNEL);
-
-		if (pcie_table == NULL)
+		pcie_table = kzalloc(struct_size(pcie_table, entries,
+						 atom_pcie_table->ucNumEntries),
+				     GFP_KERNEL);
+		if (!pcie_table)
 			return -ENOMEM;
 
 		/*
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 3d7f915381c8..535404de78a2 100644
--- a/drivers/gpu/drm/amd/pm/powerplay/hwmgr/vega10_processpptables.c
+++ b/drivers/gpu/drm/amd/pm/powerplay/hwmgr/vega10_processpptables.c
@@ -784,7 +784,7 @@ static int get_pcie_table(struct pp_hwmgr *hwmgr,
 		struct phm_ppt_v1_pcie_table **vega10_pcie_table,
 		const Vega10_PPTable_Generic_SubTable_Header *table)
 {
-	uint32_t table_size, i, pcie_count;
+	uint32_t i, pcie_count;
 	struct phm_ppt_v1_pcie_table *pcie_table;
 	struct phm_ppt_v2_information *table_info =
 			(struct phm_ppt_v2_information *)(hwmgr->pptable);
@@ -795,12 +795,8 @@ static int get_pcie_table(struct pp_hwmgr *hwmgr,
 			"Invalid PowerPlay Table!",
 			return 0);
 
-	table_size = sizeof(uint32_t) +
-			sizeof(struct phm_ppt_v1_pcie_record) *
-			atom_pcie_table->ucNumEntries;
-
-	pcie_table = kzalloc(table_size, GFP_KERNEL);
-
+	pcie_table = kzalloc(struct_size(pcie_table, entries, atom_pcie_table->ucNumEntries),
+			     GFP_KERNEL);
 	if (!pcie_table)
 		return -ENOMEM;
 
-- 
2.27.0