linux-kernel - Re: [PATCH V2] sysfs: Add sysfs_emit and sysfs_emit

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Date:   Sun, 30 Aug 2020 10:59:40 +0200 (CEST)
From:   Julia Lawall <julia.lawall@...ia.fr>
To:     Joe Perches <joe@...ches.com>
cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        "Gustavo A . R . Silva" <gustavoars@...nel.org>,
        Denis Efremov <efremov@...ux.com>,
        Julia Lawall <julia.lawall@...ia.fr>,
        Alex Dewar <alex.dewar90@...il.com>,
        Jonathan Corbet <corbet@....net>, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH V2] sysfs: Add sysfs_emit and sysfs_emit_at to format
 sysfs output



On Sat, 29 Aug 2020, Joe Perches wrote:

> On Sat, 2020-08-29 at 16:48 -0700, Joe Perches wrote:
> > Output defects can exist in sysfs content using sprintf and snprintf.
> >
> > sprintf does not know the PAGE_SIZE maximum of the temporary buffer
> > used for outputting sysfs content and it's possible to overrun the
> > PAGE_SIZE buffer length.
> >
> > Add a generic sysfs_emit function that knows that the size of the
> > temporary buffer and ensures that no overrun is done.
> >
> > Add a generic sysfs_emit_at function that can be used in multiple
> > call situations that also ensures that no overrun is done.
>
> This preliminary coccinelle script converts ~5000 instances treewide.
> There are still many remaining instances that could be converted.

Except for the issue with the ...s that has been discussed, this looks
basically reasonable to me.

julia


>
> $ git grep -w sysfs_emit -- '*.[ch]'|wc -l
> 4702
> $ git grep -w sysfs_emit_at -- '*.[ch]'|wc -l
> 229
>
> $ cat sysfs_emit.cocci
> @@
> identifier d_show =~ "^.*show.*$";
> identifier arg1, arg2, arg3;
> @@
> ssize_t d_show(struct device *
> -	arg1
> +	dev
> 	, struct device_attribute *
> -	arg2
> +	attr
> 	, char *
> -	arg3
> +	buf
> 	)
> {
> 	...
> (
> -	arg1
> +	dev
> |
> -	arg2
> +	attr
> |
> -	arg3
> +	buf
> )
> 	...
> }
>
> @@
> identifier d_show =~ "^.*show.*$";
> identifier dev, attr, buf;
> @@
>
> ssize_t d_show(struct device *dev, struct device_attribute *attr, char *buf)
> {
> 	<...
> 	return
> -	sprintf(buf,
> +	sysfs_emit(buf,
> 	...);
> 	...>
> }
>
> @@
> identifier d_show =~ "^.*show.*$";
> identifier dev, attr, buf;
> @@
>
> ssize_t d_show(struct device *dev, struct device_attribute *attr, char *buf)
> {
> 	<...
> 	return
> -	snprintf(buf, PAGE_SIZE,
> +	sysfs_emit(buf,
> 	...);
> 	...>
> }
>
> @@
> identifier d_show =~ "^.*show.*$";
> identifier dev, attr, buf;
> @@
>
> ssize_t d_show(struct device *dev, struct device_attribute *attr, char *buf)
> {
> 	<...
> 	return
> -	scnprintf(buf, PAGE_SIZE,
> +	sysfs_emit(buf,
> 	...);
> 	...>
> }
>
> @@
> identifier d_show =~ "^.*show.*$";
> identifier dev, attr, buf;
> expression chr;
> @@
>
> ssize_t d_show(struct device *dev, struct device_attribute *attr, char *buf)
> {
> 	<...
> 	return
> -	strcpy(buf, chr);
> +	sysfs_emit(buf, chr);
> 	...>
> }
>
> @@
> identifier d_show =~ "^.*show.*$";
> identifier dev, attr, buf;
> identifier len;
> @@
>
> ssize_t d_show(struct device *dev, struct device_attribute *attr, char *buf)
> {
> 	<...
> 	len =
> -	sprintf(buf,
> +	sysfs_emit(buf,
> 	...);
> 	...>
> 	return len;
> }
>
> @@
> identifier d_show =~ "^.*show.*$";
> identifier dev, attr, buf;
> identifier len;
> @@
>
> ssize_t d_show(struct device *dev, struct device_attribute *attr, char *buf)
> {
> 	<...
> 	len =
> -	snprintf(buf, PAGE_SIZE,
> +	sysfs_emit(buf,
> 	...);
> 	...>
> 	return len;
> }
>
> @@
> identifier d_show =~ "^.*show.*$";
> identifier dev, attr, buf;
> identifier len;
> @@
>
> ssize_t d_show(struct device *dev, struct device_attribute *attr, char *buf)
> {
> 	<...
> 	len =
> -	scnprintf(buf, PAGE_SIZE,
> +	sysfs_emit(buf,
> 	...);
> 	...>
> 	return len;
> }
>
> @@
> identifier d_show =~ "^.*show.*$";
> identifier dev, attr, buf;
> identifier len;
> @@
>
> ssize_t d_show(struct device *dev, struct device_attribute *attr, char *buf)
> {
> 	<...
> -	len += scnprintf(buf + len, PAGE_SIZE - len,
> +	len += sysfs_emit_at(buf, len,
> 	...);
> 	...>
> 	return len;
> }
>
> @@
> identifier d_show =~ "^.*show.*$";
> identifier dev, attr, buf;
> expression chr;
> @@
>
> ssize_t d_show(struct device *dev, struct device_attribute *attr, char *buf)
> {
> -	strcpy(buf, chr);
> -	return strlen(buf);
> +	return sysfs_emit(buf, chr);
> }
>
> @@
> identifier k_show =~ "^.*show.*$";
> identifier arg1, arg2, arg3;
> @@
> ssize_t k_show(struct kobject *
> -	arg1
> +	kobj
> 	, struct kobj_attribute *
> -	arg2
> +	attr
> 	, char *
> -	arg3
> +	buf
> 	)
> {
> 	...
> (
> -	arg1
> +	kobj
> |
> -	arg2
> +	attr
> |
> -	arg3
> +	buf
> )
> 	...
> }
>
> @@
> identifier k_show =~ "^.*show.*$";
> identifier kobj, attr, buf;
> @@
>
> ssize_t k_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf)
> {
> 	<...
> 	return
> -	sprintf(buf,
> +	sysfs_emit(buf,
> 	...);
> 	...>
> }
>
> @@
> identifier k_show =~ "^.*show.*$";
> identifier kobj, attr, buf;
> @@
>
> ssize_t k_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf)
> {
> 	<...
> 	return
> -	snprintf(buf, PAGE_SIZE,
> +	sysfs_emit(buf,
> 	...);
> 	...>
> }
>
> @@
> identifier k_show =~ "^.*show.*$";
> identifier kobj, attr, buf;
> @@
>
> ssize_t k_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf)
> {
> 	<...
> 	return
> -	scnprintf(buf, PAGE_SIZE,
> +	sysfs_emit(buf,
> 	...);
> 	...>
> }
>
> @@
> identifier k_show =~ "^.*show.*$";
> identifier kobj, attr, buf;
> expression chr;
> @@
>
> ssize_t k_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf)
> {
> 	<...
> 	return
> -	strcpy(buf, chr);
> +	sysfs_emit(buf, chr);
> 	...>
> }
>
> @@
> identifier k_show =~ "^.*show.*$";
> identifier kobj, attr, buf;
> identifier len;
> @@
>
> ssize_t k_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf)
> {
> 	<...
> 	len =
> -	sprintf(buf,
> +	sysfs_emit(buf,
> 	...);
> 	...>
> 	return len;
> }
>
> @@
> identifier k_show =~ "^.*show.*$";
> identifier kobj, attr, buf;
> identifier len;
> @@
>
> ssize_t k_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf)
> {
> 	<...
> 	len =
> -	snprintf(buf, PAGE_SIZE,
> +	sysfs_emit(buf,
> 	...);
> 	...>
> 	return len;
> }
>
> @@
> identifier k_show =~ "^.*show.*$";
> identifier kobj, attr, buf;
> identifier len;
> @@
>
> ssize_t k_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf)
> {
> 	<...
> 	len =
> -	scnprintf(buf, PAGE_SIZE,
> +	sysfs_emit(buf,
> 	...);
> 	...>
> 	return len;
> }
>
> @@
> identifier k_show =~ "^.*show.*$";
> identifier kobj, attr, buf;
> identifier len;
> @@
>
> ssize_t k_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf)
> {
> 	<...
> -	len += scnprintf(buf + len, PAGE_SIZE - len,
> +	len += sysfs_emit_at(buf, len,
> 	...);
> 	...>
> 	return len;
> }
>
> @@
> identifier k_show =~ "^.*show.*$";
> identifier kobj, attr, buf;
> expression chr;
> @@
>
> ssize_t k_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf)
> {
> -	strcpy(buf, chr);
> -	return strlen(buf);
> +	return sysfs_emit(buf, chr);
> }
>
>
>