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

    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++) {

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