ACK: [X][B][D][E][F][U][SRU][CVE-2020-11494][PATCH 1/1] slcan: Don't transmit uninitialized stack data in padding

[Colin Ian King]

On 08/04/2020 09:58, Po-Hsu Lin wrote:
> From: Richard Palethorpe <rpalethorpe at suse.com>
> 
> CVE-2020-11494
> 
> struct can_frame contains some padding which is not explicitly zeroed in
> slc_bump. This uninitialized data will then be transmitted if the stack
> initialization hardening feature is not enabled (CONFIG_INIT_STACK_ALL).
> 
> This commit just zeroes the whole struct including the padding.
> 
> Signed-off-by: Richard Palethorpe <rpalethorpe at suse.com>
> Fixes: a1044e36e457 ("can: add slcan driver for serial/USB-serial CAN adapters")
> Reviewed-by: Kees Cook <keescook at chromium.org>
> Cc: linux-can at vger.kernel.org
> Cc: netdev at vger.kernel.org
> Cc: security at kernel.org
> Cc: wg at grandegger.com
> Cc: mkl at pengutronix.de
> Cc: davem at davemloft.net
> Acked-by: Marc Kleine-Budde <mkl at pengutronix.de>
> Signed-off-by: David S. Miller <davem at davemloft.net>
> (cherry picked from commit b9258a2cece4ec1f020715fe3554bc2e360f6264)
> Signed-off-by: Po-Hsu Lin <po-hsu.lin at canonical.com>
> ---
>  drivers/net/can/slcan.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/drivers/net/can/slcan.c b/drivers/net/can/slcan.c
> index cc4a0c4..b8694b5 100644
> --- a/drivers/net/can/slcan.c
> +++ b/drivers/net/can/slcan.c
> @@ -147,7 +147,7 @@ static void slc_bump(struct slcan *sl)
>  	u32 tmpid;
>  	char *cmd = sl->rbuff;
>  
> -	cf.can_id = 0;
> +	memset(&cf, 0, sizeof(cf));
>  
>  	switch (*cmd) {
>  	case 'r':
> @@ -186,8 +186,6 @@ static void slc_bump(struct slcan *sl)
>  	else
>  		return;
>  
> -	*(u64 *) (&cf.data) = 0; /* clear payload */
> -
>  	/* RTR frames may have a dlc > 0 but they never have any data bytes */
>  	if (!(cf.can_id & CAN_RTR_FLAG)) {
>  		for (i = 0; i < cf.can_dlc; i++) {
> 
Clean cherry pick, makes sense. Thanks!

Acked-by: Colin Ian King <colin.king at canonical.com>