spi: Prevent unexpected SPI time out due to arithmetic overflow

When reading SPI flash as MTD device, the transfer length is
directly passed to the spi driver. If the requested data size
exceeds 512KB, it will cause the time out calculation to
overflow since transfer length is 32-bit unsigned integer.
This issue is resolved by using 64-bit unsigned integer
to perform the arithmetic.

Signed-off-by: Sien Wu <[email protected]>
Acked-by: Brad Keryan <[email protected]>
Acked-by: Gratian Crisan <[email protected]>
Acked-by: Brad Mouring <[email protected]>
Natinst-ReviewBoard-ID 150232
Signed-off-by: Mark Brown <[email protected]>

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index 51ad42fad567913339ab8d9deaf531b779865a87..ac889df9b1f347c96fd52a28f1b87c339a24e6c0 100644 (file)
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -960,7 +960,7 @@ static int spi_transfer_one_message(struct spi_master *master,
        struct spi_transfer *xfer;
        bool keep_cs = false;
        int ret = 0;
-       unsigned long ms = 1;
+       unsigned long long ms = 1;
        struct spi_statistics *statm = &master->statistics;
        struct spi_statistics *stats = &msg->spi->statistics;
 
@@ -991,9 +991,13 @@ static int spi_transfer_one_message(struct spi_master *master,
 
                        if (ret > 0) {
                                ret = 0;
-                               ms = xfer->len * 8 * 1000 / xfer->speed_hz;
+                               ms = 8LL * 1000LL * xfer->len;
+                               do_div(ms, xfer->speed_hz);
                                ms += ms + 100; /* some tolerance */
 
+                               if (ms > UINT_MAX)
+                                       ms = UINT_MAX;
+
                                ms = wait_for_completion_timeout(&master->xfer_completion,
                                                                 msecs_to_jiffies(ms));
                        }