linux-kernel - Re: [PATCH] virtio-blk: fixup coccinelle warnings

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Message-ID: <YXEvo5w6OzH3T0Tv@stefanha-x1.localdomain>
Date:   Thu, 21 Oct 2021 10:15:15 +0100
From:   Stefan Hajnoczi <stefanha@...hat.com>
To:     Joe Perches <joe@...ches.com>
Cc:     cgel.zte@...il.com, mst@...hat.com,
        Denis Efremov <efremov@...ux.com>,
        Julia Lawall <Julia.Lawall@...ia.fr>,
        Gilles Muller <Gilles.Muller@...ia.fr>,
        Nicolas Palix <nicolas.palix@...g.fr>,
        Michal Marek <michal.lkml@...kovi.net>, cocci@...ia.fr,
        jasowang@...hat.com, pbonzini@...hat.com, axboe@...nel.dk,
        virtualization@...ts.linux-foundation.org,
        linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        Ye Guojin <ye.guojin@....com.cn>,
        Zeal Robot <zealci@....com.cn>
Subject: Re: [PATCH] virtio-blk: fixup coccinelle warnings

On Thu, Oct 21, 2021 at 12:08:23AM -0700, Joe Perches wrote:
> On Thu, 2021-10-21 at 06:51 +0000, cgel.zte@...il.com wrote:
> > From: Ye Guojin <ye.guojin@....com.cn>
> > 
> > coccicheck complains about the use of snprintf() in sysfs show
> > functions:
> > WARNING  use scnprintf or sprintf
> > 
> > Use sysfs_emit instead of scnprintf or sprintf makes more sense.
> []
> > diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
> []
> > @@ -624,7 +624,7 @@ cache_type_show(struct device *dev, struct device_attribute *attr, char *buf)
> > -	return snprintf(buf, 40, "%s\n", virtblk_cache_types[writeback]);
> > +	return sysfs_emit(buf, "%s\n", virtblk_cache_types[writeback]);
> 
> Perhaps scripts/coccinelle/api/device_attr_show.cocci should be updated
> to be more like the script used in commit 1c7fd72687d6

This won't catch the case covered by the patch because it's
"snprintf(buf, 40" instead of "snprintf(buf, PAGE_SIZE", although
any size that's not PAGE_SIZE needs to be reviewed carefully in case the
intent of the statement is to truncate the output.

Stefan

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