linux-hardening - Re: [PATCH] printk: cleanup deprecated uses of strncpy/strcpy

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Date: Thu, 2 May 2024 17:07:08 +0200
From: Petr Mladek <pmladek@...e.com>
To: Justin Stitt <justinstitt@...gle.com>
Cc: Steven Rostedt <rostedt@...dmis.org>,
	John Ogness <john.ogness@...utronix.de>,
	Sergey Senozhatsky <senozhatsky@...omium.org>,
	linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH] printk: cleanup deprecated uses of strncpy/strcpy

On Mon 2024-04-29 23:06:54, Justin Stitt wrote:
> Cleanup some deprecated uses of strncpy() and strcpy() [1].
> 
> There doesn't seem to be any bugs with the current code but the
> readability of this code could benefit from a quick makeover while
> removing some deprecated stuff as a benefit.
> 
> The most interesting replacement made in this patch involves
> concatenating "ttyS" with a digit-led user-supplied string. Instead of
> doing two distinct string copies with carefully managed offsets and
> lengths, let's use the more robust and self-explanatory scnprintf().
> scnprintf will 1) respect the bounds of @buf, 2) null-terminate @buf, 3)
> do the concatenation. This allows us to drop the manual NUL-byte assignment.
> 
> Also, since isdigit() is used about a dozen lines after the open-coded
> version we'll replace it for uniformity's sake.
> 
> All the strcpy() --> strscpy() replacements are trivial as the source
> strings are literals and much smaller than the destination size. No
> behavioral change here.
> 
> Use the new 2-argument version of strscpy() introduced in Commit
> e6584c3964f2f ("string: Allow 2-argument strscpy()"). However, to make
> this work fully (since the size must be known at compile time), also
> update the extern-qualified declaration to have the proper size
> information.
> 
> Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [1]
> Link: https://github.com/KSPP/linux/issues/90 [2]
> Link: https://manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html [3]
> Cc: linux-hardening@...r.kernel.org
> Signed-off-by: Justin Stitt <justinstitt@...gle.com>

Nice improvements. Looks fine.

Reviewed-by: Petr Mladek <pmladek@...e.com>

Best Regards,
Petr