From: Rasmus Villemoes <linux@rasmusvillemoes.dk>
To: Yann Droneaud <ydroneaud@opteya.com>,
David Laight <David.Laight@ACULAB.COM>,
Joe Perches <joe@perches.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>, Stephen Kitt <steve@sk2.org>,
Kees Cook <keescook@chromium.org>,
Nitin Gote <nitin.r.gote@intel.com>,
"jannh@google.com" <jannh@google.com>,
"kernel-hardening@lists.openwall.com"
<kernel-hardening@lists.openwall.com>,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH 1/2] string: Add stracpy and stracpy_pad mechanisms
Date: Wed, 24 Jul 2019 15:09:10 +0200 [thread overview]
Message-ID: <396d1eed-8edf-aa77-110b-c50ead3a5fd5@rasmusvillemoes.dk> (raw)
In-Reply-To: <bc1ad99a420dd842ce3a17c2c38a2f94683dc91c.camel@opteya.com>
On 24/07/2019 14.05, Yann Droneaud wrote:
> Hi,
>
> Beware that snprintf(), per C standard, is supposed to return the
> length of the formatted string, regarless of the size of the
> destination buffer.
>
> So encouraging developper to write something like code below because
> snprintf() in kernel behave in a non-standard way,
The kernel's snprintf() does not behave in a non-standard way, at least
not with respect to its return value. It doesn't support %n or floating
point, of course, and there are some quirks regarding precision (see
lib/test_printf.c for details).
There's the non-standard scnprintf() for getting the length of the
formatted string, which can safely be used in an append loop. Or one can
use the seq_buf API.
Rasmus
next prev parent reply other threads:[~2019-07-24 13:09 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-23 0:38 [PATCH 0/2] string: Add stracpy and stracpy_pad Joe Perches
2019-07-23 0:38 ` [PATCH 1/2] string: Add stracpy and stracpy_pad mechanisms Joe Perches
2019-07-23 4:35 ` Andrew Morton
2019-07-23 4:42 ` Joe Perches
2019-07-23 21:29 ` Kees Cook
2019-07-23 6:55 ` Rasmus Villemoes
2019-07-23 15:41 ` David Laight
2019-07-23 15:50 ` Joe Perches
2019-07-23 21:34 ` Kees Cook
2019-07-24 12:05 ` Yann Droneaud
2019-07-24 13:09 ` Rasmus Villemoes [this message]
2019-07-24 17:08 ` Linus Torvalds
2019-07-25 20:03 ` Kees Cook
2019-07-26 2:46 ` Joe Perches
2019-07-23 21:36 ` Kees Cook
2019-07-24 11:40 ` Joe Perches
2019-07-23 0:38 ` [PATCH 2/2] kernel-doc: core-api: Include string.h into core-api Joe Perches
2019-07-23 21:28 ` Kees Cook
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