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

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Date: Wed, 17 Jan 2024 11:40:09 +0100
From: Markus Elfring <Markus.Elfring@....de>
To: Kunwu Chan <chentao@...inos.cn>, xen-devel@...ts.xenproject.org,
 kernel-janitors@...r.kernel.org
Cc: 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

> 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?

>  	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”?

Regards,
Markus