2015-12-27 10:17:13

by Nicolas Boichat

Subject: [PATCH] spi: mediatek: Prevent overflows in FIFO transfers

In the case where transfer length is not a multiple of 4, KASAN
reports 2 out-of-bounds memory accesses:
- mtk_spi_interrupt: ioread32_rep writes past the end of
trans->rx_buf.
- mtk_spi_fifo_transfer: iowrite32_rep reads past the end of
xfer->tx_buf.

Fix this by using memcpy on the remainder of the bytes.

Signed-off-by: Nicolas Boichat <[email protected]>
---
drivers/spi/spi-mt65xx.c | 28 ++++++++++++++++++----------
1 file changed, 18 insertions(+), 10 deletions(-)

diff --git a/drivers/spi/spi-mt65xx.c b/drivers/spi/spi-mt65xx.c
index 00a36da..8763eff 100644
--- a/drivers/spi/spi-mt65xx.c
+++ b/drivers/spi/spi-mt65xx.c
@@ -320,7 +320,8 @@ static int mtk_spi_fifo_transfer(struct spi_master *master,
struct spi_device *spi,
struct spi_transfer *xfer)
{
- int cnt;
+ int cnt, remainder;
+ u32 reg_val;
struct mtk_spi *mdata = spi_master_get_devdata(master);

mdata->cur_transfer = xfer;
@@ -328,12 +329,16 @@ static int mtk_spi_fifo_transfer(struct spi_master *master,
mtk_spi_prepare_transfer(master, xfer);
mtk_spi_setup_packet(master);

- if (xfer->len % 4)
- cnt = xfer->len / 4 + 1;
- else
- cnt = xfer->len / 4;
+ cnt = xfer->len / 4;
iowrite32_rep(mdata->base + SPI_TX_DATA_REG, xfer->tx_buf, cnt);

+ remainder = xfer->len % 4;
+ if (remainder > 0) {
+ reg_val = 0;
+ memcpy(&reg_val, xfer->tx_buf + (cnt * 4), remainder);
+ writel(reg_val, mdata->base + SPI_TX_DATA_REG);
+ }
+
mtk_spi_enable_transfer(master);

return 1;
@@ -415,7 +420,7 @@ static int mtk_spi_setup(struct spi_device *spi)

static irqreturn_t mtk_spi_interrupt(int irq, void *dev_id)
{
- u32 cmd, reg_val, cnt;
+ u32 cmd, reg_val, cnt, remainder;
struct spi_master *master = dev_id;
struct mtk_spi *mdata = spi_master_get_devdata(master);
struct spi_transfer *trans = mdata->cur_transfer;
@@ -428,12 +433,15 @@ static irqreturn_t mtk_spi_interrupt(int irq, void *dev_id)

if (!master->can_dma(master, master->cur_msg->spi, trans)) {
if (trans->rx_buf) {
- if (mdata->xfer_len % 4)
- cnt = mdata->xfer_len / 4 + 1;
- else
- cnt = mdata->xfer_len / 4;
+ cnt = mdata->xfer_len / 4;
ioread32_rep(mdata->base + SPI_RX_DATA_REG,
trans->rx_buf, cnt);
+ remainder = mdata->xfer_len % 4;
+ if (remainder > 0) {
+ reg_val = readl(mdata->base + SPI_RX_DATA_REG);
+ memcpy(trans->rx_buf + (cnt * 4),
+ &reg_val, remainder);
+ }
}
spi_finalize_current_transfer(master);
return IRQ_HANDLED;
--
2.6.0.rc2.230.g3dd15c0