From: Joe Perches <joe@perches.com>
To: Kees Cook <keescook@chromium.org>, 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>,
cocci <cocci@systeme.lip6.fr>
Subject: Re: [Cocci] [PATCH] usb: atm: don't use snprintf() for sysfs attrs
Date: Thu, 27 Aug 2020 15:45:17 -0700 [thread overview]
Message-ID: <5ebe5c2737b59d04f1b8a46008cd3159c638f9d0.camel@perches.com> (raw)
In-Reply-To: <202008271517.ECC1F1F8F@keescook>
On Thu, 2020-08-27 at 15:20 -0700, Kees Cook wrote:
> 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;
> }
It seems likely that coccinelle could do those transform
with any of sprintf/snprintf/scnprint too.
Though my bikeshed would use a single function and have
that function know the maximum output size
Something like:
With single line use:
return sysfs_emit(buf, buf, fmt, ...) - buf;
and multi-line use:
char *pos = buf;
pos = sysfs_emit(buf, pos, fmt1, ...);
pos = sysfs_emit(buf, pos, fmt2, ...);
...
return pos - buf;
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next prev parent reply other threads:[~2020-08-27 22:46 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20200824222322.22962-1-alex.dewar90@gmail.com>
[not found] ` <48f2dc90-7852-eaf1-55d7-2c85cf954688@rasmusvillemoes.dk>
[not found] ` <20200827071537.GA168593@kroah.com>
[not found] ` <20200827131819.7rcl2f5js3hkoqj2@lenovo-laptop>
[not found] ` <def24e9e-018c-9712-0d07-d4cbc84f07d9@rasmusvillemoes.dk>
[not found] ` <20200827144846.yauuttjaqtxaldxg@lenovo-laptop>
2020-08-27 16:58 ` [Cocci] [PATCH] usb: atm: don't use snprintf() for sysfs attrs Joe Perches
2020-08-27 19:42 ` Julia Lawall
2020-08-27 20:29 ` Joe Perches
2020-08-27 21:00 ` Joe Perches
2020-08-27 21:29 ` Julia Lawall
2020-08-27 22:03 ` David Laight
2020-08-27 22:11 ` Joe Perches
2020-08-27 22:16 ` Kees Cook
2020-08-27 21:01 ` Denis Efremov
2020-08-27 21:36 ` Julia Lawall
2020-08-27 21:44 ` Joe Perches
2020-08-27 22:38 ` Denis Efremov
2020-08-27 22:48 ` Joe Perches
2020-08-27 22:20 ` Kees Cook
2020-08-27 22:45 ` Joe Perches [this message]
2020-08-28 4:12 ` Joe Perches
2020-08-28 7:58 ` Kees Cook
2020-08-28 8:10 ` Joe Perches
2020-08-28 8:22 ` Joe Perches
2020-08-28 7:39 ` David Laight
2020-08-27 21:54 ` David Laight
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