Re: [PATCH] virt: acrn: replace deprecated strncpy with strscpy

From: Kees Cook <keescook@chromium.org>
To: Justin Stitt <justinstitt@google.com>
Cc: Fei Li <fei1.li@intel.com>,
	linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org
Subject: Re: [PATCH] virt: acrn: replace deprecated strncpy with strscpy
Date: Thu, 28 Mar 2024 21:05:49 -0700	[thread overview]
Message-ID: <202403282105.321DAF619B@keescook> (raw)
In-Reply-To: <20240320-strncpy-drivers-virt-acrn-ioreq-c-v1-1-db6996770341@google.com>

On Wed, Mar 20, 2024 at 11:27:09PM +0000, 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.
> 
> We can see that client->name should be NUL-terminated based on its usage
> with a %s C-string format specifier.
> |	client->thread = kthread_run(ioreq_task, client, "VM%u-%s",
> |					client->vm->vmid, client->name);
> 
> NUL-padding is not required as client is already zero-allocated:
> |	client = kzalloc(sizeof(*client), GFP_KERNEL);
> 
> Considering the above, a suitable replacement is `strscpy` [2] due to
> the fact that it guarantees NUL-termination on the destination buffer
> without unnecessarily NUL-padding.
> 
> Note that this patch relies on the _new_ 2-argument version of strscpy()
> introduced in Commit e6584c3964f2f ("string: Allow 2-argument
> strscpy()").
> 
> Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [1]
> Link: https://manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html [2]
> Link: https://github.com/KSPP/linux/issues/90
> Cc: linux-hardening@vger.kernel.org
> Signed-off-by: Justin Stitt <justinstitt@google.com>

Reviewed-by: Kees Cook <keescook@chromium.org>

-- 
Kees Cook