From: Christoph Hellwig hch@lst.de
commit e3a36eb6dfaeea8175c05d5915dcf0b939be6dab upstream.
This does three inter-related things to clarify the usage of the platform device dma_mask field. In the process, fix the bug introduced by cdfee5623290 ("driver core: initialize a default DMA mask for platform device") that caused Artem Tashkinov's laptop to not boot with newer Fedora kernels.
This does:
- First off, rename the field to "platform_dma_mask" to make it greppable.
We have way too many different random fields called "dma_mask" in various data structures, where some of them are actual masks, and some of them are just pointers to the mask. And the structures all have pointers to each other, or embed each other inside themselves, and "pdev" sometimes means "platform device" and sometimes it means "PCI device".
So to make it clear in the code when you actually use this new field, give it a unique name (it really should be something even more unique like "platform_device_dma_mask", since it's per platform device, not per platform, but that gets old really fast, and this is unique enough in context).
To further clarify when the field gets used, initialize it when we actually start using it with the default value.
- Then, use this field instead of the random one-off allocation in platform_device_register_full() that is now unnecessary since we now already have a perfectly fine allocation for it in the platform device structure.
- The above then allows us to fix the actual bug, where the error path of platform_device_register_full() would unconditionally free the platform device DMA allocation with 'kfree()'.
That kfree() was dont regardless of whether the allocation had been done earlier with the (now removed) kmalloc, or whether setup_pdev_dma_masks() had already been used and the dma_mask pointer pointed to the mask that was part of the platform device.
It seems most people never triggered the error path, or only triggered it from a call chain that set an explicit pdevinfo->dma_mask value (and thus caused the unnecessary allocation that was "cleaned up" in the error path) before calling platform_device_register_full().
Robin Murphy points out that in Artem's case the wdat_wdt driver failed in platform_device_add(), and that was the one that had called platform_device_register_full() with pdevinfo.dma_mask = 0, and would have caused that kfree() of pdev.dma_mask corrupting the heap.
A later unrelated kmalloc() then oopsed due to the heap corruption.
Fixes: cdfee5623290 ("driver core: initialize a default DMA mask for platform device") Reported-bisected-and-tested-by: Artem S. Tashkinov aros@gmx.com Reviewed-by: Robin Murphy robin.murphy@arm.com Cc: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Christoph Hellwig hch@lst.de Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/base/platform.c | 25 ++++++------------------- include/linux/platform_device.h | 2 +- 2 files changed, 7 insertions(+), 20 deletions(-)
--- a/drivers/base/platform.c +++ b/drivers/base/platform.c @@ -363,10 +363,10 @@ static void setup_pdev_dma_masks(struct { if (!pdev->dev.coherent_dma_mask) pdev->dev.coherent_dma_mask = DMA_BIT_MASK(32); - if (!pdev->dma_mask) - pdev->dma_mask = DMA_BIT_MASK(32); - if (!pdev->dev.dma_mask) - pdev->dev.dma_mask = &pdev->dma_mask; + if (!pdev->dev.dma_mask) { + pdev->platform_dma_mask = DMA_BIT_MASK(32); + pdev->dev.dma_mask = &pdev->platform_dma_mask; + } };
/** @@ -662,20 +662,8 @@ struct platform_device *platform_device_ pdev->dev.of_node_reused = pdevinfo->of_node_reused;
if (pdevinfo->dma_mask) { - /* - * This memory isn't freed when the device is put, - * I don't have a nice idea for that though. Conceptually - * dma_mask in struct device should not be a pointer. - * See http://thread.gmane.org/gmane.linux.kernel.pci/9081 - */ - pdev->dev.dma_mask = - kmalloc(sizeof(*pdev->dev.dma_mask), GFP_KERNEL); - if (!pdev->dev.dma_mask) - goto err; - - kmemleak_ignore(pdev->dev.dma_mask); - - *pdev->dev.dma_mask = pdevinfo->dma_mask; + pdev->platform_dma_mask = pdevinfo->dma_mask; + pdev->dev.dma_mask = &pdev->platform_dma_mask; pdev->dev.coherent_dma_mask = pdevinfo->dma_mask; }
@@ -700,7 +688,6 @@ struct platform_device *platform_device_ if (ret) { err: ACPI_COMPANION_SET(&pdev->dev, NULL); - kfree(pdev->dev.dma_mask); platform_device_put(pdev); return ERR_PTR(ret); } --- a/include/linux/platform_device.h +++ b/include/linux/platform_device.h @@ -24,7 +24,7 @@ struct platform_device { int id; bool id_auto; struct device dev; - u64 dma_mask; + u64 platform_dma_mask; u32 num_resources; struct resource *resource;