linux-kernel - Re: [PATCH] drm/nouveau/nvif: use struct

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Message-ID: <a3905de3-265a-b69b-10f7-044bc18808b0@nfschina.com>
Date:   Thu, 1 Jun 2023 08:59:32 +0800
From:   Su Hui <suhui@...china.com>
To:     Dan Carpenter <dan.carpenter@...aro.org>
Cc:     Ben Skeggs <bskeggs@...hat.com>, Karol Herbst <kherbst@...hat.com>,
        Lyude Paul <lyude@...hat.com>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>, airlied@...hat.com,
        dri-devel@...ts.freedesktop.org, nouveau@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: Re: [PATCH] drm/nouveau/nvif: use struct_size()

On 2023/5/31 16:31, Dan Carpenter wrote:
> On Wed, May 31, 2023 at 12:38:26PM +0800, Su Hui wrote:
>> Use struct_size() instead of hand writing it.
>> This is less verbose and more informative.
>>
>> Signed-off-by: Su Hui <suhui@...china.com>
>> ---
>>   drivers/gpu/drm/nouveau/nvif/object.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/nouveau/nvif/object.c b/drivers/gpu/drm/nouveau/nvif/object.c
>> index 4d1aaee8fe15..4bd693aa4ee0 100644
>> --- a/drivers/gpu/drm/nouveau/nvif/object.c
>> +++ b/drivers/gpu/drm/nouveau/nvif/object.c
>> @@ -65,7 +65,7 @@ nvif_object_sclass_get(struct nvif_object *object, struct nvif_sclass **psclass)
>>   	u32 size;
>>   
>>   	while (1) {
>> -		size = sizeof(*args) + cnt * sizeof(args->sclass.oclass[0]);
>> +		size = struct_size(args, sclass.oclass, cnt);
> This is from the original code, but now that you are using the
> struct_size() macro static checkers will complain about it.  (Maybe they
> don't yet?).  size is a u32.  Never save struct_size() returns to
> anything except unsigned long or size_t.  (ssize_t is also fine, I
> suppose).  Otherwise, you do not benefit from the integer overflow
> checking.
Sorry, I don't notice the issue caused by type size.
You are right, this patch is wrong because of the type mismatch.
Thanks for your reply!

Su Hui

>>   		if (!(args = kmalloc(size, GFP_KERNEL)))
>>   			return -ENOMEM;
>>   		args->ioctl.version = 0;
> regards,
> dan carpenter