linux-kernel - Re: [PATCH v2] tracing: replace multiple deprecated strncpy with memcpy

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <202410141423.2C30F35EE0@keescook>
Date: Mon, 14 Oct 2024 14:31:29 -0700
From: Kees Cook <kees@...nel.org>
To: Justin Stitt <justinstitt@...gle.com>
Cc: Steven Rostedt <rostedt@...dmis.org>,
	Masami Hiramatsu <mhiramat@...nel.org>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org,
	linux-hardening@...r.kernel.org
Subject: Re: [PATCH v2] tracing: replace multiple deprecated strncpy with
 memcpy

On Mon, Oct 14, 2024 at 02:13:14PM -0700, Justin Stitt wrote:
> strncpy() is deprecated for use on NUL-terminated destination strings [1] and
> as such we should prefer more robust and less ambiguous string interfaces.
> 
> String copy operations involving manual pointer offset and length
> calculations followed by explicit NUL-byte assignments are best changed
> to either strscpy or memcpy.
> 
> strscpy is not a drop-in replacement as @len would need a one subtracted
> from it to avoid truncating the source string.
> 
> To not sabotage readability of the current code, use memcpy (retaining
> the manual NUL assignment) as this unambiguously describes the desired
> behavior.

We know the destination must have a NUL-terminated string. Is the src
NUL terminated? Looking at parse_pred(), it seems like no? And we can't
use memtostr_pad() here because the source buffer size isn't known at
compile time. Okay then. And there are no NUL bytes in the "str + s"
span, so yeah, it looks like memcpy() is best.

Reviewed-by: Kees Cook <kees@...nel.org>

-- 
Kees Cook