Re: [PATCH] arch:x86:coco:sev: Initialize ctxt variable

[Tom Lendacky]

On 11/18/24 08:44, Tom Lendacky wrote:
> On 11/15/24 16:55, Ard Biesheuvel wrote:
>> On Fri, 15 Nov 2024 at 20:53, Ragavendra B.N. <ragavendra.bn@xxxxxxxxx> wrote:
>>>
>>> On Fri, Nov 15, 2024 at 12:02:27PM +0100, Ard Biesheuvel wrote:
>>>> On Fri, 15 Nov 2024 at 12:01, Ingo Molnar <mingo@xxxxxxxxxx> wrote:
>>>>>
>>>>>
>>>>> * Ragavendra <ragavendra.bn@xxxxxxxxx> wrote:
>>>>>
>>>>>> Updating the ctxt value to NULL in the svsm_perform_ghcb_protocol as
>>>>>> it was not initialized.
>>>>>>
>>>>>> Fixes: 2e1b3cc9d7f7 (grafted) Merge tag 'arm-fixes-6.12-2' of git://git.kernel.org/pub/scm/linux/kernel/git/soc/soc
>>>>>
>>>>> This 'Fixes' tag looks bogus.
>>>>>
>>>>
>>>> So does the patch itself - 'struct es_em_ctxt ctxt' is not a pointer.
>>> Thank you very much for your response. I am relatively new to kernel development.
>>>
>>> I know we can use kmalloc for memory allocation. Please advice.
>>>
>>> struct es_em_ctxt ctxt = kmalloc(sizeof(struct es_em_ctxt), GFP_KERNEL);
>>>
>>> I am thinking to update like above, but like you mentioned, ctxt is not a pointer. I can update this to be a pointer if needed.
>>>
>>
>> The code is fine as is. Let's end this thread here, shall we?
> 
> I was assuming he got some kind of warning from some compiler options or
> a static checker. Is that the case Ragavendra?
> 
> When I look at the code, it is possible for ctxt->fi.error_code to be
> left uninitialized. The simple fix is to just initialize ctxt as:
> 
> 	struct es_em_ctxt ctxt = {};

Although to cover all cases now and going forwared, the es_em_ctxt fi
member should just be zeroed in verify_exception_info() when
ES_EXCEPTION is going to be returned.

Thanks,
Tom

> 
> Thanks,
> Tom