linux-kernel - Re: [PATCH v2] usbip: usbip_host: Replace strlcpy with strscpy

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Message-ID: <785c1d49-f080-2f21-2948-d12d522c9fa7@linuxfoundation.org>
Date:   Wed, 14 Jun 2023 09:02:10 -0600
From:   Shuah Khan <skhan@...uxfoundation.org>
To:     Azeem Shaikh <azeemshaikh38@...il.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Valentina Manea <valentina.manea.m@...il.com>,
        Shuah Khan <shuah@...nel.org>,
        Kees Cook <keescook@...omium.org>
Cc:     linux-hardening@...r.kernel.org, Hongren Zheng <i@...ithal.me>,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        Shuah Khan <skhan@...uxfoundation.org>
Subject: Re: [PATCH v2] usbip: usbip_host: Replace strlcpy with strscpy

On 6/14/23 08:10, 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>
> ---
> v1: https://lore.kernel.org/all/20230613004402.3540432-1-azeemshaikh38@gmail.com/
> 
> Changes from v1 - uses "< 0" instead of "== -E2BIG".
> 
>   drivers/usb/usbip/stub_main.c |    3 +--
>   1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/drivers/usb/usbip/stub_main.c b/drivers/usb/usbip/stub_main.c
> index e8c3131a8543..97043b4df275 100644
> --- a/drivers/usb/usbip/stub_main.c
> +++ b/drivers/usb/usbip/stub_main.c
> @@ -174,8 +174,7 @@ static ssize_t match_busid_store(struct device_driver *dev, const char *buf,
>   		return -EINVAL;
>   
>   	/* busid needs to include \0 termination */
> -	len = strlcpy(busid, buf + 4, BUSID_SIZE);
> -	if (sizeof(busid) <= len)
> +	if (strscpy(busid, buf + 4, BUSID_SIZE) < 0)
>   		return -EINVAL;
>   
>   	if (!strncmp(buf, "add ", 4)) {


Than you Kees for the review.

If Kees is happy, I am happy :)

Acked-by: Shuah Khan <skhan@...uxfoundation.org>

thanks,
-- Shuah