linux-hardening - Re: [PATCH v2] crypto: Replace strlcpy with strscpy

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Message-ID: <202306201311.862B05981F@keescook>
Date:   Tue, 20 Jun 2023 13:12:08 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Azeem Shaikh <azeemshaikh38@...il.com>
Cc:     Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Biggers <ebiggers@...nel.org>,
        linux-hardening@...r.kernel.org, linux-crypto@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] crypto: Replace strlcpy with strscpy

On Tue, Jun 20, 2023 at 08:08:32PM +0000, Azeem Shaikh wrote:
> strlcpy() reads the entire source buffer first.
> This read may exceed the destination size limit.
> This is both inefficient and can lead to linear read
> overflows if a source string is not NUL-terminated [1].
> In an effort to remove strlcpy() completely [2], replace
> strlcpy() here with strscpy().
> 
> Direct replacement is safe here since return value of -errno
> is used to check for truncation instead of sizeof(dest).
> 
> [1] https://www.kernel.org/doc/html/latest/process/deprecated.html#strlcpy
> [2] https://github.com/KSPP/linux/issues/89
> 
> Signed-off-by: Azeem Shaikh <azeemshaikh38@...il.com>

Thanks for fixing up the variable type. (And thank you Eric for catching
the signedness problem!)

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

-- 
Kees Cook