[PATCH v2] slcan: Don't transmit uninitialized stack data in padding

[PATCH v2] slcan: Don't transmit uninitialized stack data in padding

[Richard Palethorpe]

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@suse.com>
Fixes: a1044e36e457 ("can: add slcan driver for serial/USB-serial CAN adapters")
Reviewed-by: Kees Cook <keescook@chromium.org>
Cc: linux-can@vger.kernel.org
Cc: netdev@vger.kernel.org
Cc: security@kernel.org
Cc: wg@grandegger.com
Cc: mkl@pengutronix.de
Cc: davem@davemloft.net
---

V2: Reviewed by Kees and Fixes tag added.

As mentioned in V1; The following unfinished test can reproduce the bug:
https://github.com/richiejp/ltp/blob/pty-slcan/testcases/kernel/pty/pty04.c


 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 a3664281a33f..4dfa459ef5c7 100644
--- a/drivers/net/can/slcan.c
+++ b/drivers/net/can/slcan.c
@@ -148,7 +148,7 @@ 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':
@@ -187,8 +187,6 @@ 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++) {
-- 
2.24.0

Re: [PATCH v2] slcan: Don't transmit uninitialized stack data in padding

[Marc Kleine-Budde]

On 4/1/20 12:06 PM, Richard Palethorpe wrote:
> 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@suse.com>
> Fixes: a1044e36e457 ("can: add slcan driver for serial/USB-serial CAN adapters")
> Reviewed-by: Kees Cook <keescook@chromium.org>
> Cc: linux-can@vger.kernel.org
> Cc: netdev@vger.kernel.org
> Cc: security@kernel.org
> Cc: wg@grandegger.com
> Cc: mkl@pengutronix.de
> Cc: davem@davemloft.net

Acked-by: Marc Kleine-Budde <mkl@pengutronix.de>

Marc

-- 
Pengutronix e.K.                 | Marc Kleine-Budde           |
Embedded Linux                   | https://www.pengutronix.de  |
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Re: [PATCH v2] slcan: Don't transmit uninitialized stack data in padding

[David Miller]

From: Richard Palethorpe <rpalethorpe@suse.com>
Date: Wed,  1 Apr 2020 12:06:39 +0200

> 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@suse.com>
> Fixes: a1044e36e457 ("can: add slcan driver for serial/USB-serial CAN adapters")
> Reviewed-by: Kees Cook <keescook@chromium.org>

Applied and queued up for -stable, thanks.

Re: [PATCH v2] slcan: Don't transmit uninitialized stack data in padding

[Oliver Hartkopp]

On 01/04/2020 12.06, Richard Palethorpe wrote:
> 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@suse.com>
> Fixes: a1044e36e457 ("can: add slcan driver for serial/USB-serial CAN adapters")
> Reviewed-by: Kees Cook <keescook@chromium.org>
> Cc: linux-can@vger.kernel.org
> Cc: netdev@vger.kernel.org
> Cc: security@kernel.org
> Cc: wg@grandegger.com
> Cc: mkl@pengutronix.de
> Cc: davem@davemloft.net

Acked-by: Oliver Hartkopp <socketcan@hartkopp.net>


> ---
> 
> V2: Reviewed by Kees and Fixes tag added.
> 
> As mentioned in V1; The following unfinished test can reproduce the bug:
> https://github.com/richiejp/ltp/blob/pty-slcan/testcases/kernel/pty/pty04.c
> 
> 
>   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 a3664281a33f..4dfa459ef5c7 100644
> --- a/drivers/net/can/slcan.c
> +++ b/drivers/net/can/slcan.c
> @@ -148,7 +148,7 @@ 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':
> @@ -187,8 +187,6 @@ 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++) {
>