summaryrefslogtreecommitdiff
path: root/drivers/dma
diff options
context:
space:
mode:
authorLogan Gunthorpe <logang@deltatee.com>2019-12-16 12:01:16 -0700
committerVinod Koul <vkoul@kernel.org>2019-12-24 10:18:32 +0530
commitdae7a589c18a4d979d5f14b09374e871b995ceb1 (patch)
treeb788a32e2ed73ecd8fbe3961f95456b2b9dc66e9 /drivers/dma
parent20f5a659554a6e684da0806939bddf8f6537e936 (diff)
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: Logan Gunthorpe <logang@deltatee.com> Link: https://lore.kernel.org/r/20191216190120.21374-2-logang@deltatee.com Signed-off-by: Vinod Koul <vkoul@kernel.org>
Diffstat (limited to 'drivers/dma')
-rw-r--r--drivers/dma/dmaengine.c4
1 files changed, 3 insertions, 1 deletions
diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c
index 03ac4b96117c..4b604086b1b3 100644
--- a/drivers/dma/dmaengine.c
+++ b/drivers/dma/dmaengine.c
@@ -179,7 +179,7 @@ __dma_device_satisfies_mask(struct dma_device *device,
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)
return -EIO;
}
+ device->owner = device->dev->driver->owner;
+
if (dma_has_cap(DMA_MEMCPY, device->cap_mask) && !device->device_prep_dma_memcpy) {
dev_err(device->dev,
"Device claims capability %s, but op is not defined\n",