[PATCH] spi: spidev: prevent spidev->speed_hz from being zero

[PATCH] spi: spidev: prevent spidev->speed_hz from being zero

[Dan Carpenter]

A zero value for spi->max_speed_hz or spidev->speed_hz does not make
sense and trying to set that can lead to divide by zero crashes in
a some of the drivers.

drivers/spi/spi-s3c64xx.c:874 s3c64xx_spi_setup() error: potential divide by zero bug '/ spi->max_speed_hz'.
drivers/spi/spi-fsl-dspi.c:613 hz_to_spi_baud() error: potential divide by zero bug '/ speed_hz'.
drivers/spi/spi-xlp.c:146 xlp_spi_setup() error: potential divide by zero bug '/ (spi->max_speed_hz)'.
drivers/spi/spi-orion.c:162 orion_spi_baudrate_set() error: potential divide by zero bug '/ speed'.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
---
It's hard to know which Fixes tag to use...

 drivers/spi/spidev.c | 31 +++++++++++++++++++------------
 1 file changed, 19 insertions(+), 12 deletions(-)

diff --git a/drivers/spi/spidev.c b/drivers/spi/spidev.c
index a5cceca8b82b..dd824db63fbe 100644
--- a/drivers/spi/spidev.c
+++ b/drivers/spi/spidev.c
@@ -453,22 +453,29 @@ spidev_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 				dev_dbg(&spi->dev, "%d bits per word\n", tmp);
 		}
 		break;
-	case SPI_IOC_WR_MAX_SPEED_HZ:
+	case SPI_IOC_WR_MAX_SPEED_HZ: {
+		u32 save;
+
 		retval = get_user(tmp, (__u32 __user *)arg);
-		if (retval == 0) {
-			u32	save = spi->max_speed_hz;
+		if (retval)
+			break;
+		if (tmp == 0) {
+			retval = -EINVAL;
+			break;
+		}
 
-			spi->max_speed_hz = tmp;
-			retval = spi_setup(spi);
-			if (retval == 0) {
-				spidev->speed_hz = tmp;
-				dev_dbg(&spi->dev, "%d Hz (max)\n",
-					spidev->speed_hz);
-			}
-			spi->max_speed_hz = save;
+		save = spi->max_speed_hz;
+
+		spi->max_speed_hz = tmp;
+		retval = spi_setup(spi);
+		if (retval == 0) {
+			spidev->speed_hz = tmp;
+			dev_dbg(&spi->dev, "%d Hz (max)\n", spidev->speed_hz);
 		}
-		break;
 
+		spi->max_speed_hz = save;
+		break;
+	}
 	default:
 		/* segmented and/or full-duplex I/O request */
 		/* Check message and copy into scratch area */
-- 
2.20.1

Re: [PATCH] spi: spidev: prevent spidev->speed_hz from being zero

[Mark Brown]

On Tue, 25 Jan 2022 09:52:02 +0300, Dan Carpenter wrote:
> A zero value for spi->max_speed_hz or spidev->speed_hz does not make
> sense and trying to set that can lead to divide by zero crashes in
> a some of the drivers.
> 
> drivers/spi/spi-s3c64xx.c:874 s3c64xx_spi_setup() error: potential divide by zero bug '/ spi->max_speed_hz'.
> drivers/spi/spi-fsl-dspi.c:613 hz_to_spi_baud() error: potential divide by zero bug '/ speed_hz'.
> drivers/spi/spi-xlp.c:146 xlp_spi_setup() error: potential divide by zero bug '/ (spi->max_speed_hz)'.
> drivers/spi/spi-orion.c:162 orion_spi_baudrate_set() error: potential divide by zero bug '/ speed'.
> 
> [...]

Applied to

   https://git.kernel.org/pub/scm/linux/kernel/git/broonie/spi.git for-next

Thanks!

[1/1] spi: spidev: prevent spidev->speed_hz from being zero
      commit: 833026ad56f76d1a1035d6511fd5aeed308465fd

All being well this means that it will be integrated into the linux-next
tree (usually sometime in the next 24 hours) and sent to Linus during
the next merge window (or sooner if it is a bug fix), however if
problems are discovered then the patch may be dropped or reverted.

You may get further e-mails resulting from automated or manual testing
and review of the tree, please engage with people reporting problems and
send followup patches addressing any issues that are reported if needed.

If any updates are required or you are submitting further changes they
should be sent as incremental updates against current git, existing
patches will not be replaced.

Please add any relevant lists and maintainers to the CCs when replying
to this mail.

Thanks,
Mark