[PATCH AUTOSEL 5.6 068/129] slcan: Don't transmit uninitialized stack data in padding

[PATCH AUTOSEL 5.6 068/129] slcan: Don't transmit uninitialized stack data in padding

[Sasha Levin]

From: Richard Palethorpe <rpalethorpe@suse.com>

[ Upstream commit b9258a2cece4ec1f020715fe3554bc2e360f6264 ]

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>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 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 a3664281a33fc..4dfa459ef5c73 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++) {
-- 
2.20.1

Re: [PATCH AUTOSEL 5.6 068/129] slcan: Don't transmit uninitialized stack data in padding

[Eric W. Biederman]

How does this differ from Greg's backports of this patches?

Sasha Levin <sashal@kernel.org> writes:

> From: Richard Palethorpe <rpalethorpe@suse.com>
>
> [ Upstream commit b9258a2cece4ec1f020715fe3554bc2e360f6264 ]
>
> 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>
> Signed-off-by: David S. Miller <davem@davemloft.net>
> Signed-off-by: Sasha Levin <sashal@kernel.org>
> ---
>  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 a3664281a33fc..4dfa459ef5c73 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++) {

Re: [PATCH AUTOSEL 5.6 068/129] slcan: Don't transmit uninitialized stack data in padding

[Greg KH]

On Wed, Apr 15, 2020 at 12:09:08PM -0500, Eric W. Biederman wrote:
> 
> How does this differ from Greg's backports of this patches?

His tool didn't catch that they are already in a merged tree, it's a few
steps later that this happens :)

greg k-h

Re: [PATCH AUTOSEL 5.6 068/129] slcan: Don't transmit uninitialized stack data in padding

[Sasha Levin]

On Wed, Apr 15, 2020 at 07:22:43PM +0200, Greg KH wrote:
>On Wed, Apr 15, 2020 at 12:09:08PM -0500, Eric W. Biederman wrote:
>>
>> How does this differ from Greg's backports of this patches?
>
>His tool didn't catch that they are already in a merged tree, it's a few
>steps later that this happens :)

My process for doing these takes a day or two (or three) to build test,
test, and send mails. Sometimes Greg beats me to it :)

-- 
Thanks,
Sasha