linux-kernel - Re: [PATCH 2/2] powerpc/xive: Add a check for memory allocation failure

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Date:   Thu, 1 Aug 2019 11:41:32 +0200
From:   Greg Kurz <groug@...d.org>
To:     Christophe JAILLET <christophe.jaillet@...adoo.fr>
Cc:     benh@...nel.crashing.org, paulus@...ba.org, mpe@...erman.id.au,
        allison@...utok.net, tglx@...utronix.de, clg@...d.org,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        kernel-janitors@...r.kernel.org
Subject: Re: [PATCH 2/2] powerpc/xive: Add a check for memory allocation
 failure

On Thu,  1 Aug 2019 10:32:42 +0200
Christophe JAILLET <christophe.jaillet@...adoo.fr> wrote:

> The result of this kzalloc is not checked. Add a check and corresponding
> error handling code.
> 
> Signed-off-by: Christophe JAILLET <christophe.jaillet@...adoo.fr>
> ---

Reviewed-by: Greg Kurz <groug@...d.org>

> Note that 'xive_irq_bitmap_add()' failures are not handled in
> 'xive_spapr_init()'
> I guess that it is not really an issue. This function is _init, so if a
> memory allocation occures here, it is likely that the system will
> already be in bad shape.

Hmm not sure... The allocation could also fail if the "ibm,xive-lisn-ranges"
property contains an insanely big range, eg. count == 1 << 31. The system isn't
necessarily in bad shape in this case, but XIVE is definitely unusable and
we should let a chance to the kernel to switch to XICS in this case.

I guess it is worth adding proper error handling in xive_spapr_init() as well.

> Anyway, the check added here would at least keep the data linked in
> 'xive_irq_bitmaps' usable.
> ---
>  arch/powerpc/sysdev/xive/spapr.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/arch/powerpc/sysdev/xive/spapr.c b/arch/powerpc/sysdev/xive/spapr.c
> index b4f5eb9e0f82..52198131c75e 100644
> --- a/arch/powerpc/sysdev/xive/spapr.c
> +++ b/arch/powerpc/sysdev/xive/spapr.c
> @@ -53,6 +53,10 @@ static int xive_irq_bitmap_add(int base, int count)
>  	xibm->base = base;
>  	xibm->count = count;
>  	xibm->bitmap = kzalloc(xibm->count, GFP_KERNEL);
> +	if (!xibm->bitmap) {
> +		kfree(xibm);
> +		return -ENOMEM;
> +	}
>  	list_add(&xibm->list, &xive_irq_bitmaps);
>  
>  	pr_info("Using IRQ range [%x-%x]", xibm->base,