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From: Kees Cook <keescook@chromium.org>
To: Denis Efremov <efremov@linux.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	linux-usb@vger.kernel.org,
	Rasmus Villemoes <linux@rasmusvillemoes.dk>,
	"Gustavo A. R. Silva" <gustavoars@kernel.org>,
	linux-kernel@vger.kernel.org, Alex Dewar <alex.dewar90@gmail.com>,
	accessrunner-general@lists.sourceforge.net,
	Joe Perches <joe@perches.com>, cocci <cocci@systeme.lip6.fr>
Subject: Re: [Cocci] [PATCH] usb: atm: don't use snprintf() for sysfs attrs
Date: Thu, 27 Aug 2020 15:20:54 -0700	[thread overview]
Message-ID: <202008271517.ECC1F1F8F@keescook> (raw)
In-Reply-To: <5853c58e-7d26-2cf9-6cbf-698ecd93cbf9@linux.com>

On Fri, Aug 28, 2020 at 12:01:34AM +0300, Denis Efremov wrote:
> Just FYI, I've send an addition to the device_attr_show.cocci script[1] to turn
> simple cases of snprintf (e.g. "%i") to sprintf. Looks like many developers would
> like it more than changing snprintf to scnprintf. As for me, I don't like the idea
> of automated altering of the original logic from bounded snprint to unbouded one
> with sprintf.

Agreed. This just makes me cringe. If the API design declares that when
a show() callback starts, buf has been allocated with PAGE_SIZE bytes,
then that's how the logic should proceed, and it should be using
scnprintf...

show(...) {
	size_t remaining = PAGE_SIZE;

	...
	remaining -= scnprintf(buf, remaining, "fmt", var args ...);
	remaining -= scnprintf(buf, remaining, "fmt", var args ...);
	remaining -= scnprintf(buf, remaining, "fmt", var args ...);

	return PAGE_SIZE - remaining;
}

-- 
Kees Cook
_______________________________________________
Cocci mailing list
Cocci@systeme.lip6.fr
https://systeme.lip6.fr/mailman/listinfo/cocci

WARNING: multiple messages have this Message-ID (diff)
From: Kees Cook <keescook@chromium.org>
To: Denis Efremov <efremov@linux.com>
Cc: Julia Lawall <julia.lawall@inria.fr>,
	Joe Perches <joe@perches.com>,
	"Gustavo A. R. Silva" <gustavoars@kernel.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	linux-usb@vger.kernel.org,
	Rasmus Villemoes <linux@rasmusvillemoes.dk>,
	linux-kernel@vger.kernel.org, cocci <cocci@systeme.lip6.fr>,
	accessrunner-general@lists.sourceforge.net,
	Alex Dewar <alex.dewar90@gmail.com>
Subject: Re: [Cocci] [PATCH] usb: atm: don't use snprintf() for sysfs attrs
Date: Thu, 27 Aug 2020 15:20:54 -0700	[thread overview]
Message-ID: <202008271517.ECC1F1F8F@keescook> (raw)
In-Reply-To: <5853c58e-7d26-2cf9-6cbf-698ecd93cbf9@linux.com>

On Fri, Aug 28, 2020 at 12:01:34AM +0300, Denis Efremov wrote:
> Just FYI, I've send an addition to the device_attr_show.cocci script[1] to turn
> simple cases of snprintf (e.g. "%i") to sprintf. Looks like many developers would
> like it more than changing snprintf to scnprintf. As for me, I don't like the idea
> of automated altering of the original logic from bounded snprint to unbouded one
> with sprintf.

Agreed. This just makes me cringe. If the API design declares that when
a show() callback starts, buf has been allocated with PAGE_SIZE bytes,
then that's how the logic should proceed, and it should be using
scnprintf...

show(...) {
	size_t remaining = PAGE_SIZE;

	...
	remaining -= scnprintf(buf, remaining, "fmt", var args ...);
	remaining -= scnprintf(buf, remaining, "fmt", var args ...);
	remaining -= scnprintf(buf, remaining, "fmt", var args ...);

	return PAGE_SIZE - remaining;
}

-- 
Kees Cook

  parent reply	other threads:[~2020-08-27 22:21 UTC|newest]

Thread overview: 54+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-08-24 22:23 [PATCH] usb: atm: don't use snprintf() for sysfs attrs Alex Dewar
2020-08-25  8:12 ` David Laight
2020-08-25  8:17   ` Alex Dewar
2020-08-25  9:07     ` David Laight
2020-08-25  8:24   ` Greg Kroah-Hartman
2020-08-27 16:49     ` Kees Cook
2020-08-27 17:45       ` Greg Kroah-Hartman
2020-08-27  6:42 ` Rasmus Villemoes
2020-08-27  7:15   ` Greg Kroah-Hartman
2020-08-27 13:18     ` Alex Dewar
2020-08-27 13:41       ` Rasmus Villemoes
2020-08-27 14:48         ` Alex Dewar
2020-08-27 16:58           ` [Cocci] " Joe Perches
2020-08-27 16:58             ` Joe Perches
2020-08-27 19:42             ` [Cocci] " Julia Lawall
2020-08-27 19:42               ` Julia Lawall
2020-08-27 20:29               ` Joe Perches
2020-08-27 20:29                 ` Joe Perches
2020-08-27 21:00                 ` Joe Perches
2020-08-27 21:00                   ` Joe Perches
2020-08-27 21:29                 ` Julia Lawall
2020-08-27 21:29                   ` Julia Lawall
2020-08-27 22:03                 ` David Laight
2020-08-27 22:03                   ` David Laight
2020-08-27 22:11                   ` Joe Perches
2020-08-27 22:11                     ` Joe Perches
2020-08-27 22:16                     ` Kees Cook
2020-08-27 22:16                       ` Kees Cook
2020-08-27 21:01               ` Denis Efremov
2020-08-27 21:01                 ` Denis Efremov
2020-08-27 21:36                 ` Julia Lawall
2020-08-27 21:36                   ` Julia Lawall
2020-08-27 21:44                   ` Joe Perches
2020-08-27 21:44                     ` Joe Perches
2020-08-27 22:38                     ` Denis Efremov
2020-08-27 22:38                       ` Denis Efremov
2020-08-27 22:48                       ` Joe Perches
2020-08-27 22:48                         ` Joe Perches
2020-08-27 22:20                 ` Kees Cook [this message]
2020-08-27 22:20                   ` Kees Cook
2020-08-27 22:45                   ` Joe Perches
2020-08-27 22:45                     ` Joe Perches
2020-08-28  4:12                     ` Joe Perches
2020-08-28  4:12                       ` Joe Perches
2020-08-28  7:58                       ` Kees Cook
2020-08-28  7:58                         ` Kees Cook
2020-08-28  8:10                         ` Joe Perches
2020-08-28  8:10                           ` Joe Perches
2020-08-28  8:22                           ` Joe Perches
2020-08-28  8:22                             ` Joe Perches
2020-08-28  7:39                   ` David Laight
2020-08-28  7:39                     ` David Laight
2020-08-27 21:54             ` David Laight
2020-08-27 21:54               ` David Laight

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