Commit dae7a589 authored by Logan Gunthorpe's avatar Logan Gunthorpe Committed by Vinod Koul

dmaengine: Store module owner in dma_device struct

dma_chan_to_owner() dereferences the driver from the struct device to
obtain the owner and call module_[get|put](). However, if the backing
device is unbound before the dma_device is unregistered, the driver
will be cleared and this will cause a NULL pointer dereference.

Instead, store a pointer to the owner module in the dma_device struct
so the module reference can be properly put when the channel is put, even
if the backing device was destroyed first.

This change helps to support a safer unbind of DMA engines.
If the dma_device is unregistered in the driver's remove function,
there's no guarantee that there are no existing clients and a users
action may trigger the WARN_ONCE in dma_async_device_unregister()
which is unlikely to leave the system in a consistent state.
Instead, a better approach is to allow the backing driver to go away
and fail any subsequent requests to it.
Signed-off-by: default avatarLogan Gunthorpe <logang@deltatee.com>
Link: https://lore.kernel.org/r/20191216190120.21374-2-logang@deltatee.comSigned-off-by: default avatarVinod Koul <vkoul@kernel.org>
parent 20f5a659
...@@ -179,7 +179,7 @@ __dma_device_satisfies_mask(struct dma_device *device, ...@@ -179,7 +179,7 @@ __dma_device_satisfies_mask(struct dma_device *device,
static struct module *dma_chan_to_owner(struct dma_chan *chan) static struct module *dma_chan_to_owner(struct dma_chan *chan)
{ {
return chan->device->dev->driver->owner; return chan->device->owner;
} }
/** /**
...@@ -919,6 +919,8 @@ int dma_async_device_register(struct dma_device *device) ...@@ -919,6 +919,8 @@ int dma_async_device_register(struct dma_device *device)
return -EIO; return -EIO;
} }
device->owner = device->dev->driver->owner;
if (dma_has_cap(DMA_MEMCPY, device->cap_mask) && !device->device_prep_dma_memcpy) { if (dma_has_cap(DMA_MEMCPY, device->cap_mask) && !device->device_prep_dma_memcpy) {
dev_err(device->dev, dev_err(device->dev,
"Device claims capability %s, but op is not defined\n", "Device claims capability %s, but op is not defined\n",
......
...@@ -674,6 +674,7 @@ struct dma_filter { ...@@ -674,6 +674,7 @@ struct dma_filter {
* @fill_align: alignment shift for memset operations * @fill_align: alignment shift for memset operations
* @dev_id: unique device ID * @dev_id: unique device ID
* @dev: struct device reference for dma mapping api * @dev: struct device reference for dma mapping api
* @owner: owner module (automatically set based on the provided dev)
* @src_addr_widths: bit mask of src addr widths the device supports * @src_addr_widths: bit mask of src addr widths the device supports
* Width is specified in bytes, e.g. for a device supporting * Width is specified in bytes, e.g. for a device supporting
* a width of 4 the mask should have BIT(4) set. * a width of 4 the mask should have BIT(4) set.
...@@ -737,6 +738,7 @@ struct dma_device { ...@@ -737,6 +738,7 @@ struct dma_device {
int dev_id; int dev_id;
struct device *dev; struct device *dev;
struct module *owner;
u32 src_addr_widths; u32 src_addr_widths;
u32 dst_addr_widths; u32 dst_addr_widths;
......
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