Re: [PATCH] staging: r8188eu: Check for NULL header value

From: Greg Kroah-Hartman
Date: Thu Jan 13 2022 - 04:15:42 EST


On Wed, Jan 12, 2022 at 04:19:34PM -0800, Kees Cook wrote:
> When building with -Warray-bounds, the following warning is emitted:
>
> In file included from ./include/linux/string.h:253,
> from ./arch/x86/include/asm/page_32.h:22,
> from ./arch/x86/include/asm/page.h:14,
> from ./arch/x86/include/asm/thread_info.h:12,
> from ./include/linux/thread_info.h:60,
> from ./arch/x86/include/asm/preempt.h:7,
> from ./include/linux/preempt.h:78,
> from ./include/linux/rcupdate.h:27,
> from ./include/linux/rculist.h:11,
> from ./include/linux/sched/signal.h:5,
> from ./drivers/staging/rtl8723bs/include/drv_types.h:17,
> from drivers/staging/rtl8723bs/core/rtw_recv.c:7:
> In function 'memcpy',
> inlined from 'wlanhdr_to_ethhdr' at drivers/staging/rtl8723bs/core/rtw_recv.c:1554:2:
> ./include/linux/fortify-string.h:41:33: warning: '__builtin_memcpy' offset [0, 5] is out of the bounds [0, 0] [-Warray-bounds]
> 41 | #define __underlying_memcpy __builtin_memcpy
> | ^
>
> This is because the compiler sees it is possible for "ptr" to be a NULL
> value, and concludes that it has zero size and attempts to copy to it
> would overflow. Instead, detect the NULL return and error out early.
>
> Cc: Larry Finger <Larry.Finger@xxxxxxxxxxxx>
> Cc: Phillip Potter <phil@xxxxxxxxxxxxxxxx>
> Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> Cc: Michael Straube <straube.linux@xxxxxxxxx>
> Cc: Fabio Aiuto <fabioaiuto83@xxxxxxxxx>
> Cc: linux-staging@xxxxxxxxxxxxxxx
> Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
> ---
> drivers/staging/r8188eu/core/rtw_recv.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/drivers/staging/r8188eu/core/rtw_recv.c b/drivers/staging/r8188eu/core/rtw_recv.c
> index 51a13262a226..93b0aa5688e3 100644
> --- a/drivers/staging/r8188eu/core/rtw_recv.c
> +++ b/drivers/staging/r8188eu/core/rtw_recv.c
> @@ -1191,6 +1191,9 @@ static int wlanhdr_to_ethhdr(struct recv_frame *precvframe)
> u8 *ptr = get_recvframe_data(precvframe); /* point to frame_ctrl field */
> struct rx_pkt_attrib *pattrib = &precvframe->attrib;
>
> + if (!ptr)
> + return _FAIL;

Same objection as on the other staging driver change, this is not the
correct way to solve this.

thanks,

greg k-h