linux-kernel - Re: [PATCH] soc: fsl: dpio: avoid stack usage warning

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Date:   Wed, 8 Apr 2020 21:24:21 +0100
From:   Russell King - ARM Linux admin <linux@...linux.org.uk>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     soc@...nel.org, Roy Pledge <Roy.Pledge@....com>,
        Li Yang <leoyang.li@....com>,
        Youri Querry <youri.querry_1@....com>,
        Ioana Ciornei <ioana.ciornei@....com>,
        linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] soc: fsl: dpio: avoid stack usage warning

On Wed, Apr 08, 2020 at 08:58:16PM +0200, Arnd Bergmann wrote:
> A 1024 byte variable on the stack will warn on any 32-bit architecture
> during compile-testing, and is generally a bad idea anyway:
> 
> fsl/dpio/dpio-service.c: In function 'dpaa2_io_service_enqueue_multiple_desc_fq':
> fsl/dpio/dpio-service.c:495:1: error: the frame size of 1032 bytes is larger than 1024 bytes [-Werror=frame-larger-than=]
> 
> There are currently no callers of this function, so I cannot tell whether
> dynamic memory allocation is allowed once callers are added. Change
> it to kcalloc for now, if anyone gets a warning about calling this in
> atomic context after they start using it, they can fix it later.
> 
> Fixes: 9d98809711ae ("soc: fsl: dpio: Adding QMAN multiple enqueue interface")
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
>  drivers/soc/fsl/dpio/dpio-service.c | 18 +++++++++++++-----
>  1 file changed, 13 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/soc/fsl/dpio/dpio-service.c b/drivers/soc/fsl/dpio/dpio-service.c
> index cd4f6410e8c2..ff0ef8cbdbff 100644
> --- a/drivers/soc/fsl/dpio/dpio-service.c
> +++ b/drivers/soc/fsl/dpio/dpio-service.c
> @@ -478,12 +478,17 @@ int dpaa2_io_service_enqueue_multiple_desc_fq(struct dpaa2_io *d,
>  				const struct dpaa2_fd *fd,
>  				int nb)
>  {
> -	int i;
> -	struct qbman_eq_desc ed[32];
> +	struct qbman_eq_desc *ed = kcalloc(sizeof(struct qbman_eq_desc), 32, GFP_KERNEL);

I think you need to rearrange this to be more compliant with the coding
style.

> +	int i, ret;
> +
> +	if (!ed)
> +		return -ENOMEM;
>  
>  	d = service_select(d);
> -	if (!d)
> -		return -ENODEV;
> +	if (!d) {
> +		ret = -ENODEV;
> +		goto out;
> +	}
>  
>  	for (i = 0; i < nb; i++) {
>  		qbman_eq_desc_clear(&ed[i]);
> @@ -491,7 +496,10 @@ int dpaa2_io_service_enqueue_multiple_desc_fq(struct dpaa2_io *d,
>  		qbman_eq_desc_set_fq(&ed[i], fqid[i]);
>  	}
>  
> -	return qbman_swp_enqueue_multiple_desc(d->swp, &ed[0], fd, nb);
> +	ret = qbman_swp_enqueue_multiple_desc(d->swp, &ed[0], fd, nb);
> +out:
> +	kfree(ed);
> +	return ret;
>  }
>  EXPORT_SYMBOL(dpaa2_io_service_enqueue_multiple_desc_fq);
>  
> -- 
> 2.26.0
> 
> 

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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