[PATCH] spi: fsl-dspi: fix use-after-free in remove path

[PATCH] spi: fsl-dspi: fix use-after-free in remove path

[Sascha Hauer]

spi_unregister_controller() not only unregisters the controller, but
also frees the controller. This will free the driver data with it, so
we must not access it later dspi_remove().

Solve this by allocating the driver data separately from the SPI
controller.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
---

This fixes the issue reported at https://marc.info/?l=linux-spi&m=160068648808293&w=2
for the fsl-dspi driver in the way Mark suggested. A whole lot of other SPI drivers
are affected by this issue and need a similar fix. Here is a fix for the driver
I currently care about.

 drivers/spi/spi-fsl-dspi.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/drivers/spi/spi-fsl-dspi.c b/drivers/spi/spi-fsl-dspi.c
index 91c6affe139c..aae9f9a7aea6 100644
--- a/drivers/spi/spi-fsl-dspi.c
+++ b/drivers/spi/spi-fsl-dspi.c
@@ -1273,11 +1273,14 @@ static int dspi_probe(struct platform_device *pdev)
 	void __iomem *base;
 	bool big_endian;
 
-	ctlr = spi_alloc_master(&pdev->dev, sizeof(struct fsl_dspi));
+	dspi = devm_kzalloc(&pdev->dev, sizeof(*dspi), GFP_KERNEL);
+	if (!dspi)
+		return -ENOMEM;
+
+	ctlr = spi_alloc_master(&pdev->dev, 0);
 	if (!ctlr)
 		return -ENOMEM;
 
-	dspi = spi_controller_get_devdata(ctlr);
 	dspi->pdev = pdev;
 	dspi->ctlr = ctlr;
 
@@ -1414,7 +1417,7 @@ static int dspi_probe(struct platform_device *pdev)
 	if (dspi->devtype_data->trans_mode != DSPI_DMA_MODE)
 		ctlr->ptp_sts_supported = true;
 
-	platform_set_drvdata(pdev, ctlr);
+	platform_set_drvdata(pdev, dspi);
 
 	ret = spi_register_controller(ctlr);
 	if (ret != 0) {
@@ -1437,8 +1440,7 @@ static int dspi_probe(struct platform_device *pdev)
 
 static int dspi_remove(struct platform_device *pdev)
 {
-	struct spi_controller *ctlr = platform_get_drvdata(pdev);
-	struct fsl_dspi *dspi = spi_controller_get_devdata(ctlr);
+	struct fsl_dspi *dspi = platform_get_drvdata(pdev);
 
 	/* Disconnect from the SPI framework */
 	spi_unregister_controller(dspi->ctlr);
-- 
2.28.0

Re: [PATCH] spi: fsl-dspi: fix use-after-free in remove path

[Mark Brown]

On Wed, 23 Sep 2020 15:10:26 +0200, Sascha Hauer wrote:
> spi_unregister_controller() not only unregisters the controller, but
> also frees the controller. This will free the driver data with it, so
> we must not access it later dspi_remove().
> 
> Solve this by allocating the driver data separately from the SPI
> controller.

Applied to

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

Thanks!

[1/1] spi: fsl-dspi: fix use-after-free in remove path
      commit: 530b5affc675ade5db4a03f04ed7cd66806c8a1a

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