[PATCH] Race condition in mpc52xx_psc_spi

[PATCH] Race condition in mpc52xx_psc_spi

[Stefano Babic]

The RFNUM register is read only once to get the number of bytes
in the RXFIFO. If additional bytes are received during the for
loop that transfers data from the FIFO, the RFNUM register will not be
set to zero after the reading.
This causes that the RXFIFO interrupt remains pending, because
the interrupt is removed after all bytes are read from the RXFIFO
(with granularity set to 0 as set by the driver).

Signed-off-by: Stefano Babic <sbabic-ynQEQJNshbs@public.gmane.org>
---
 drivers/spi/mpc52xx_psc_spi.c |   18 ++++++++++--------
 1 files changed, 10 insertions(+), 8 deletions(-)

diff --git a/drivers/spi/mpc52xx_psc_spi.c b/drivers/spi/mpc52xx_psc_spi.c
index 8bd39df..e91d91a 100644
--- a/drivers/spi/mpc52xx_psc_spi.c
+++ b/drivers/spi/mpc52xx_psc_spi.c
@@ -191,17 +191,19 @@ static int mpc52xx_psc_spi_transfer_rxtx(struct spi_device *spi,
 		}
 		out_be16(&psc->mpc52xx_psc_imr, MPC52xx_PSC_IMR_RXRDY);
 		wait_for_completion(&mps->done);
-		recv_at_once = in_be16(&fifo->rfnum);
-		dev_dbg(&spi->dev, "%d bytes received\n", recv_at_once);
 
-		send_at_once = recv_at_once;
-		if (rx_buf) {
-			for (; recv_at_once; rb++, recv_at_once--)
-				rx_buf[rb] = in_8(&psc->mpc52xx_psc_buffer_8);
-		} else {
-			for (; recv_at_once; rb++, recv_at_once--)
+		recv_at_once = 0;
+		while (in_be16(&fifo->rfnum)) {
+			recv_at_once++;
+			if (rx_buf) {
+				rx_buf[rb++] = in_8(&psc->mpc52xx_psc_buffer_8);
+			} else {
 				in_8(&psc->mpc52xx_psc_buffer_8);
+				rb++;
+			}
 		}
+		dev_dbg(&spi->dev, "%d bytes received\n", recv_at_once);
+		send_at_once = recv_at_once;
 	}
 	/* disable transmiter/receiver */
 	out_8(&psc->command, MPC52xx_PSC_TX_DISABLE | MPC52xx_PSC_RX_DISABLE);
-- 
1.5.4.3


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