can: flexcan: fix NULL pointer exception during bringup

Commit cbffaf7aa09e ("can: flexcan: Always use last mailbox for TX")
introduced a loop letting i run up to (including) ARRAY_SIZE(regs->mb)
and in the body accessed regs->mb[i] which is an out-of-bounds array
access that then resulted in an access to an reserved register area.

Later this was changed by commit 0517961ccdf1 ("can: flexcan: Add
provision for variable payload size") to iterate a bit differently but
still runs one iteration too much resulting to call

	flexcan_get_mb(priv, priv->mb_count)

which results in a WARN_ON and then a NULL pointer exception. This
only affects devices compatible with "fsl,p1010-flexcan",
"fsl,imx53-flexcan", "fsl,imx35-flexcan", "fsl,imx25-flexcan",
"fsl,imx28-flexcan", so newer i.MX SoCs are not affected.

Fixes: cbffaf7aa09e ("can: flexcan: Always use last mailbox for TX")
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Cc: linux-stable <stable@vger.kernel.org> # >= 4.20
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

diff --git a/drivers/net/can/flexcan.c b/drivers/net/can/flexcan.c
index 5f097648d12d51f2da07e9610536a8eec18ef537..1c66fb2ad76bebbfbcdce793d0685fef5a627773 100644 (file)
--- a/drivers/net/can/flexcan.c
+++ b/drivers/net/can/flexcan.c
@@ -1106,7 +1106,7 @@ static int flexcan_chip_start(struct net_device *dev)
                }
        } else {
                /* clear and invalidate unused mailboxes first */
-               for (i = FLEXCAN_TX_MB_RESERVED_OFF_FIFO; i <= priv->mb_count; i++) {
+               for (i = FLEXCAN_TX_MB_RESERVED_OFF_FIFO; i < priv->mb_count; i++) {
                        mb = flexcan_get_mb(priv, i);
                        priv->write(FLEXCAN_MB_CODE_RX_INACTIVE,
                                    &mb->can_ctrl);