linux-kernel - Re: [PATCH v2] ext4: replace strcpy() with '.' assignment

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Message-ID: <20250523142449.GB1414791@mit.edu>
Date: Fri, 23 May 2025 10:24:49 -0400
From: "Theodore Ts'o" <tytso@....edu>
To: David Laight <david.laight.linux@...il.com>
Cc: Kees Cook <kees@...nel.org>,
        Ethan Carter Edwards <ethan@...ancedwards.com>,
        Andreas Dilger <adilger.kernel@...ger.ca>, linux-ext4@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH v2] ext4: replace strcpy() with '.' assignment

On Fri, May 23, 2025 at 01:31:00PM +0100, David Laight wrote:
> 
> The compiler (or headers files) can also allow strcpy() of constant
> length strings into arrays (known size). Erroring requests that are too long.
> The strcpy() is then converted to a memcpy() which can then be optimised
> into writes of constants.
> 
> So using strcpy() under those conditions 'isn't all bad' and can generate
> better (and less bug prone) code than trying to hand-optimise it.
> 
> So even through strcpy() is usually a bad idea, there is not need to
> remove the calls that the compiler can validate as safe.

I assume that what the hardening folks want to do is to assert that
strcpy is always evil(tm) so they can detect potential security bugs
by doing "git grep strcpy".

						- Ted