From: Will McVicker Date: Thu, 24 Apr 2025 18:04:19 +0000 (-0700) Subject: platform: Fix race condition during DMA configure at IOMMU probe time X-Git-Tag: v6.15-rc6~8^2 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=95deee37a12364f410d22c6a8383f59738a2fef3;p=thirdparty%2Fkernel%2Flinux.git platform: Fix race condition during DMA configure at IOMMU probe time To avoid a race between the IOMMU probing thread and the device driver async probing thread during configuration of the platform DMA, update `platform_dma_configure()` to read `dev->driver` once and test if it's NULL before using it. This ensures that we don't de-reference an invalid platform driver pointer if the device driver is asynchronously bound while configuring the DMA. Fixes: bcb81ac6ae3c ("iommu: Get DT/ACPI parsing into the proper probe path") Signed-off-by: Will McVicker Reviewed-by: Robin Murphy Link: https://lore.kernel.org/r/20250424180420.3928523-1-willmcvicker@google.com Signed-off-by: Greg Kroah-Hartman --- diff --git a/drivers/base/platform.c b/drivers/base/platform.c index 1813cfd0c4bdf..cfccf3ff36e76 100644 --- a/drivers/base/platform.c +++ b/drivers/base/platform.c @@ -1440,7 +1440,7 @@ static void platform_shutdown(struct device *_dev) static int platform_dma_configure(struct device *dev) { - struct platform_driver *drv = to_platform_driver(dev->driver); + struct device_driver *drv = READ_ONCE(dev->driver); struct fwnode_handle *fwnode = dev_fwnode(dev); enum dev_dma_attr attr; int ret = 0; @@ -1451,8 +1451,8 @@ static int platform_dma_configure(struct device *dev) attr = acpi_get_dma_attr(to_acpi_device_node(fwnode)); ret = acpi_dma_configure(dev, attr); } - /* @drv may not be valid when we're called from the IOMMU layer */ - if (ret || !dev->driver || drv->driver_managed_dma) + /* @dev->driver may not be valid when we're called from the IOMMU layer */ + if (ret || !drv || to_platform_driver(drv)->driver_managed_dma) return ret; ret = iommu_device_use_default_domain(dev);