2023-06-13 01:17:45

by Azeem Shaikh

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

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 <[email protected]>
---
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

2023-06-13 19:59:52

by Kees Cook

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

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 <[email protected]>
> ---
> 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

2023-06-14 14:50:40

by Azeem Shaikh

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

On Tue, Jun 13, 2023 at 3:31 PM Kees Cook <[email protected]> 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 <[email protected]>
> > ---
> > 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