spi/spi_mpc8xxx: fix potential memory corruption.

tx_dma/rx_dma are already set to a dummy buffer when no
tx/rx buffer and t->tx_dma/t->rx_dma does not contain a dma
address, but NULL.
This may lead to corruption of kernel memory. Fix this by
leaving tx_dma/rx_dma alone.

Do not INIT_TX_RX while controller is enabled, this is bad according
to the MPC8321 manual.

Signed-off-by: Joakim Tjernlund <Joakim.Tjernlund@transmode.se>
Acked-by: Anton Vorontsov <cbouatmailru@gmail.com>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>

1 files changed, 3 insertions, 4 deletions

diff --git a/drivers/spi/spi_mpc8xxx.c b/drivers/spi/spi_mpc8xxx.c
index 14d052316502..0dfc482bbff5 100644
--- a/drivers/spi/spi_mpc8xxx.c
+++ b/drivers/spi/spi_mpc8xxx.c
@@ -241,7 +241,6 @@ static void mpc8xxx_spi_change_mode(struct spi_device *spi)
 
         /* Turn off SPI unit prior changing mode */
         mpc8xxx_spi_write_reg(mode, cs->hw_mode & ~SPMODE_ENABLE);
-        mpc8xxx_spi_write_reg(mode, cs->hw_mode);
 
         /* When in CPM mode, we need to reinit tx and rx. */
         if (mspi->flags & SPI_CPM_MODE) {
@@ -258,7 +257,7 @@ static void mpc8xxx_spi_change_mode(struct spi_device *spi)
                         }
                 }
         }
-
+        mpc8xxx_spi_write_reg(mode, cs->hw_mode);
         local_irq_restore(flags);
 }
 
@@ -438,7 +437,7 @@ static int mpc8xxx_spi_cpm_bufs(struct mpc8xxx_spi *mspi,
                         dev_err(dev, "unable to map tx dma\n");
                         return -ENOMEM;
                 }
-        } else {
+        } else if (t->tx_buf) {
                 mspi->tx_dma = t->tx_dma;
         }
 
@@ -449,7 +448,7 @@ static int mpc8xxx_spi_cpm_bufs(struct mpc8xxx_spi *mspi,
                         dev_err(dev, "unable to map rx dma\n");
                         goto err_rx_dma;
                 }
-        } else {
+        } else if (t->rx_buf) {
                 mspi->rx_dma = t->rx_dma;
         }