[PATCH] usbip: usbip_host: Replace strlcpy with strscpy

[PATCH] usbip: usbip_host: Replace strlcpy with strscpy

[Azeem Shaikh]

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 -E2BIG
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@gmail.com>
---
 drivers/usb/usbip/stub_main.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/usbip/stub_main.c b/drivers/usb/usbip/stub_main.c
index e8c3131a8543..a92a284f5abb 100644
--- a/drivers/usb/usbip/stub_main.c
+++ b/drivers/usb/usbip/stub_main.c
@@ -174,8 +174,8 @@ 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)
+	len = strscpy(busid, buf + 4, BUSID_SIZE);
+	if (len == -E2BIG)
 		return -EINVAL;
 
 	if (!strncmp(buf, "add ", 4)) {
-- 
2.41.0.162.gfafddb0af9-goog

Re: [PATCH] usbip: usbip_host: Replace strlcpy with strscpy

[Kees Cook]

On Tue, Jun 13, 2023 at 12:44:02AM +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 -E2BIG
> 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@gmail.com>
> ---
>  drivers/usb/usbip/stub_main.c |    4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/usb/usbip/stub_main.c b/drivers/usb/usbip/stub_main.c
> index e8c3131a8543..a92a284f5abb 100644
> --- a/drivers/usb/usbip/stub_main.c
> +++ b/drivers/usb/usbip/stub_main.c
> @@ -174,8 +174,8 @@ 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)
> +	len = strscpy(busid, buf + 4, BUSID_SIZE);
> +	if (len == -E2BIG)
>  		return -EINVAL;

"len" is never used again, so maybe:

	if (strscpy(...) < 0)
		return -EINVAL;

-Kees

>  
>  	if (!strncmp(buf, "add ", 4)) {
> -- 
> 2.41.0.162.gfafddb0af9-goog
> 
> 

-- 
Kees Cook

Re: [PATCH] usbip: usbip_host: Replace strlcpy with strscpy

[Azeem Shaikh]

On Tue, Jun 13, 2023 at 3:31 PM Kees Cook <keescook@chromium.org> wrote:
>
> On Tue, Jun 13, 2023 at 12:44:02AM +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 -E2BIG
> > 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@gmail.com>
> > ---
> >  drivers/usb/usbip/stub_main.c |    4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/usb/usbip/stub_main.c b/drivers/usb/usbip/stub_main.c
> > index e8c3131a8543..a92a284f5abb 100644
> > --- a/drivers/usb/usbip/stub_main.c
> > +++ b/drivers/usb/usbip/stub_main.c
> > @@ -174,8 +174,8 @@ 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)
> > +     len = strscpy(busid, buf + 4, BUSID_SIZE);
> > +     if (len == -E2BIG)
> >               return -EINVAL;
>
> "len" is never used again, so maybe:
>
>         if (strscpy(...) < 0)
>                 return -EINVAL;
>
> -Kees
>

Thanks. Sent v2.

> >
> >       if (!strncmp(buf, "add ", 4)) {
> > --
> > 2.41.0.162.gfafddb0af9-goog
> >
> >
>
> --
> Kees Cook