linux-kernel - Re: [PATCH v2] x86/xen: Add some null pointer checking to smp.c

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Date: Mon, 22 Jan 2024 16:41:14 +0800
From: Kunwu Chan <chentao@...inos.cn>
To: Dan Carpenter <dan.carpenter@...aro.org>
Cc: Markus Elfring <Markus.Elfring@....de>, xen-devel@...ts.xenproject.org,
 kernel-janitors@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
 kernel test robot <lkp@...el.com>,
 Boris Ostrovsky <boris.ostrovsky@...cle.com>, Borislav Petkov
 <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>,
 "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
 Jürgen Groß <jgross@...e.com>,
 Thomas Gleixner <tglx@...utronix.de>, x86@...nel.org
Subject: Re: [PATCH v2] x86/xen: Add some null pointer checking to smp.c

On 2024/1/22 16:30, Dan Carpenter wrote:
> On Fri, Jan 19, 2024 at 05:22:25PM +0800, Kunwu Chan wrote:
>> On 2024/1/17 18:40, Markus Elfring wrote:
>>>> kasprintf() returns a pointer to dynamically allocated memory
>>>> which can be NULL upon failure. Ensure the allocation was successful
>>>> by checking the pointer validity.
>>> …
>>>> +++ b/arch/x86/xen/smp.c
>>>> @@ -61,10 +61,14 @@ void xen_smp_intr_free(unsigned int cpu)
>>>>
>>>>    int xen_smp_intr_init(unsigned int cpu)
>>>>    {
>>>> -	int rc;
>>>> +	int rc = 0;
>>>
>>> I find the indication of a successful function execution sufficient by
>>> the statement “return 0;” at the end.
>>> How do you think about to omit such an extra variable initialisation?
>> Thanks, it's no need now. I'll remove it in v3.
> 
> This advice is good.  Don't do unnecessary assignments.
Thanks for your suggestions, I'll keep it in mind.
> 
>>>
>>>
>>>>    	char *resched_name, *callfunc_name, *debug_name;
>>>>
>>>>    	resched_name = kasprintf(GFP_KERNEL, "resched%d", cpu);
>>>> +	if (!resched_name) {
>>>> +		rc = -ENOMEM;
>>>> +		goto fail;
>>>> +	}
>>>>    	per_cpu(xen_resched_irq, cpu).name = resched_name;
>>>>    	rc = bind_ipi_to_irqhandler(XEN_RESCHEDULE_VECTOR,
>>>>    				    cpu,
>>>
>>> You propose to apply the same error code in four if branches.
>>> I suggest to avoid the specification of duplicate assignment statements
>>> for this purpose.
>>> How do you think about to use another label like “e_nomem”?
>> I'll add a new label to simply the code.
> 
> I'm not a Xen maintainer so I can't really comment on their style
> choices.  However, as one of the kernel-janitors list people, I would
> say that not everyone agrees with Markus's style preferences.  Markus
> was banned from the list for a while, but we unbanned everyone when we
> transitioned to the new list infrastructure.  Do a search on lore to
> find out more.  https://lore.kernel.org/all/?q=Elfring
> 
> Perhaps wait for feedback from the maintainers for how to proceed?
OK, I'll wait for the feedback.
> 
> regards,
> dan carpenter
> 
-- 
Thanks,
   Kunwu