linux-kernel - [PATCH] drm/nouveau/nvif/mmu: Use struct

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Message-ID: <20190807155002.GA25502@embeddedor>
Date:   Wed, 7 Aug 2019 10:50:02 -0500
From:   "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To:     Ben Skeggs <bskeggs@...hat.com>, David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>
Cc:     dri-devel@...ts.freedesktop.org, nouveau@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>
Subject: [PATCH] drm/nouveau/nvif/mmu: Use struct_size() helper

One of the more common cases of allocation size calculations is finding
the size of a structure that has a zero-sized array at the end, along
with memory for some number of elements for that array. For example:

struct nvif_mmu_kind_v0 {
	...
        __u8  data[];
};


Make use of the struct_size() helper instead of an open-coded version
in order to avoid any potential type mistakes.

So, replace the following form:

sizeof(*kind) + sizeof(*kind->data) * mmu->kind_nr

with:

struct_size(kind, data, mmu->kind_nr)

This code was detected with the help of Coccinelle.

Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>
---
 drivers/gpu/drm/nouveau/nvif/mmu.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/nouveau/nvif/mmu.c b/drivers/gpu/drm/nouveau/nvif/mmu.c
index ae08a1ca8044..5641bda2046d 100644
--- a/drivers/gpu/drm/nouveau/nvif/mmu.c
+++ b/drivers/gpu/drm/nouveau/nvif/mmu.c
@@ -110,7 +110,7 @@ nvif_mmu_init(struct nvif_object *parent, s32 oclass, struct nvif_mmu *mmu)
 
 	if (mmu->kind_nr) {
 		struct nvif_mmu_kind_v0 *kind;
-		u32 argc = sizeof(*kind) + sizeof(*kind->data) * mmu->kind_nr;
+		size_t argc = struct_size(kind, data, mmu->kind_nr);
 
 		if (ret = -ENOMEM, !(kind = kmalloc(argc, GFP_KERNEL)))
 			goto done;
-- 
2.22.0