linux-kernel - Re: [PATCH] inotify: Use strscpy() for event->name copies

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Message-ID: <Z2D6FzPgomC442vW@casper.infradead.org>
Date: Tue, 17 Dec 2024 04:12:07 +0000
From: Matthew Wilcox <willy@...radead.org>
To: Kees Cook <kees@...nel.org>
Cc: Jan Kara <jack@...e.cz>, Amir Goldstein <amir73il@...il.com>,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-hardening@...r.kernel.org
Subject: Re: [PATCH] inotify: Use strscpy() for event->name copies

On Mon, Dec 16, 2024 at 02:45:15PM -0800, Kees Cook wrote:
> Since we have already allocated "len + 1" space for event->name, make sure
> that name->name cannot ever accidentally cause a copy overflow by calling
> strscpy() instead of the unbounded strcpy() routine. This assists in
> the ongoing efforts to remove the unsafe strcpy() API[1] from the kernel.

Since a qstr can't contain a NUL before the length, why not just use
memcpy()?

>  	event->name_len = len;
>  	if (len)
> -		strcpy(event->name, name->name);
> +		strscpy(event->name, name->name, event->name_len + 1);