spi: loopback-test: fix potential integer overflow on multiple

A multiplication of 8U * xfer-len with the type of a 32 bit unsigned int
is evaluated using 32 bit arithmetic and then used in a context that
expects an expression of type unsigned long long (64 bits).  Avoid any
potential overflow by casting BITS_PER_BYTE to unsigned long long.

Detected by CoverityScan, CID#1419691 ("Unintentional integer overflow")

Fixes: ea9936f324356 ("spi: loopback-test: add elapsed time check")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

diff --git a/drivers/spi/spi-loopback-test.c b/drivers/spi/spi-loopback-test.c
index fcae3377ec268684e87042162bba0dccc3d612f8..6888d5c34ac470c4eadd2d5791c175ba9f7d79e8 100644 (file)
--- a/drivers/spi/spi-loopback-test.c
+++ b/drivers/spi/spi-loopback-test.c
@@ -508,7 +508,8 @@ static int spi_test_check_elapsed_time(struct spi_device *spi,
 
        for (i = 0; i < test->transfer_count; i++) {
                struct spi_transfer *xfer = test->transfers + i;
-               unsigned long long nbits = BITS_PER_BYTE * xfer->len;
+               unsigned long long nbits = (unsigned long long)BITS_PER_BYTE *
+                                          xfer->len;
 
                delay_usecs += xfer->delay_usecs;
                if (!xfer->speed_hz)