r8152: Avoid memcpy() over-reading of ETH_SS_STATS

Message ID 20210616195303.1231429-1-keescook@chromium.org
State New
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Series
  • r8152: Avoid memcpy() over-reading of ETH_SS_STATS
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Commit Message

Kees Cook June 16, 2021, 7:53 p.m.
In preparation for FORTIFY_SOURCE performing compile-time and run-time
field bounds checking for memcpy(), memmove(), and memset(), avoid
intentionally reading across neighboring array fields.

The memcpy() is copying the entire structure, not just the first array.
Adjust the source argument so the compiler can do appropriate bounds
checking.

Signed-off-by: Kees Cook <keescook@chromium.org>
---
 drivers/net/usb/r8152.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Comments

Andrew Lunn June 16, 2021, 8:02 p.m. | #1
On Wed, Jun 16, 2021 at 12:53:03PM -0700, Kees Cook wrote:
> In preparation for FORTIFY_SOURCE performing compile-time and run-time
> field bounds checking for memcpy(), memmove(), and memset(), avoid
> intentionally reading across neighboring array fields.
> 
> The memcpy() is copying the entire structure, not just the first array.
> Adjust the source argument so the compiler can do appropriate bounds
> checking.
> 
> Signed-off-by: Kees Cook <keescook@chromium.org>
> ---
>  drivers/net/usb/r8152.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/usb/r8152.c b/drivers/net/usb/r8152.c
> index 85039e17f4cd..5f08720bf1c9 100644
> --- a/drivers/net/usb/r8152.c
> +++ b/drivers/net/usb/r8152.c
> @@ -8678,7 +8678,7 @@ static void rtl8152_get_strings(struct net_device *dev, u32 stringset, u8 *data)
>  {
>  	switch (stringset) {
>  	case ETH_SS_STATS:
> -		memcpy(data, *rtl8152_gstrings, sizeof(rtl8152_gstrings));
> +		memcpy(data, rtl8152_gstrings, sizeof(rtl8152_gstrings));
>  		break;

Is this correct? The call is supposed to return all the statistic
strings, which would be the entire structure.

	  Andrew
Andrew Lunn June 16, 2021, 8:10 p.m. | #2
On Wed, Jun 16, 2021 at 10:02:43PM +0200, Andrew Lunn wrote:
> On Wed, Jun 16, 2021 at 12:53:03PM -0700, Kees Cook wrote:
> > In preparation for FORTIFY_SOURCE performing compile-time and run-time
> > field bounds checking for memcpy(), memmove(), and memset(), avoid
> > intentionally reading across neighboring array fields.
> > 
> > The memcpy() is copying the entire structure, not just the first array.
> > Adjust the source argument so the compiler can do appropriate bounds
> > checking.
> > 
> > Signed-off-by: Kees Cook <keescook@chromium.org>
> > ---
> >  drivers/net/usb/r8152.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/net/usb/r8152.c b/drivers/net/usb/r8152.c
> > index 85039e17f4cd..5f08720bf1c9 100644
> > --- a/drivers/net/usb/r8152.c
> > +++ b/drivers/net/usb/r8152.c
> > @@ -8678,7 +8678,7 @@ static void rtl8152_get_strings(struct net_device *dev, u32 stringset, u8 *data)
> >  {
> >  	switch (stringset) {
> >  	case ETH_SS_STATS:
> > -		memcpy(data, *rtl8152_gstrings, sizeof(rtl8152_gstrings));
> > +		memcpy(data, rtl8152_gstrings, sizeof(rtl8152_gstrings));
> >  		break;
> 
> Is this correct? The call is supposed to return all the statistic
> strings, which would be the entire structure.

Ah! now i think i get it.

Although *rtl8152_gstrings == rtl8152_gstrings in terms of addresses,
the compiler sees that *rtl8152_gstrings is sizeof(ETH_GSTRING_LEN),
but we are copying sizeof(rtl8152_gstrings), so it will issue a
warning. So you remove the * to indicate we are interesting in the
whole structure of arrays.

      Andrew

Patch

diff --git a/drivers/net/usb/r8152.c b/drivers/net/usb/r8152.c
index 85039e17f4cd..5f08720bf1c9 100644
--- a/drivers/net/usb/r8152.c
+++ b/drivers/net/usb/r8152.c
@@ -8678,7 +8678,7 @@  static void rtl8152_get_strings(struct net_device *dev, u32 stringset, u8 *data)
 {
 	switch (stringset) {
 	case ETH_SS_STATS:
-		memcpy(data, *rtl8152_gstrings, sizeof(rtl8152_gstrings));
+		memcpy(data, rtl8152_gstrings, sizeof(rtl8152_gstrings));
 		break;
 	}
 }