Messages in this thread Patch in this message | | | From | Kamal Mostafa <> | Subject | [PATCH 3.19.y-ckt 20/86] cxl: Fix unbalanced pci_dev_get in cxl_probe | Date | Tue, 27 Oct 2015 14:29:20 -0700 |
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3.19.8-ckt9 -stable review patch. If anyone has any objections, please let me know.
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From: Daniel Axtens <dja@axtens.net>
commit 2925c2fdf1e0eb642482f5b30577e9435aaa8edb upstream.
Currently the first thing we do in cxl_probe is to grab a reference on the pci device. Later on, we call device_register on our adapter. In our remove path, we call device_unregister, but we never call pci_dev_put. We therefore leak the device every time we do a reflash.
device_register/unregister is sufficient to hold the reference. Therefore, drop the call to pci_dev_get.
Here's why this is safe. The proposed cxl_probe(pdev) calls cxl_adapter_init: a) init calls cxl_adapter_alloc, which creates a struct cxl, conventionally called adapter. This struct contains a device entry, adapter->dev.
b) init calls cxl_configure_adapter, where we set adapter->dev.parent = &dev->dev (here dev is the pci dev)
So at this point, the cxl adapter's device's parent is the PCI device that I want to be refcounted properly.
c) init calls cxl_register_adapter *) cxl_register_adapter calls device_register(&adapter->dev)
So now we're in device_register, where dev is the adapter device, and we want to know if the PCI device is safe after we return.
device_register(&adapter->dev) calls device_initialize() and then device_add().
device_add() does a get_device(). device_add() also explicitly grabs the device's parent, and calls get_device() on it:
parent = get_device(dev->parent);
So therefore, device_register() takes a lock on the parent PCI dev, which is what pci_dev_get() was guarding. pci_dev_get() can therefore be safely removed.
Fixes: f204e0b8cedd ("cxl: Driver code for powernv PCIe based cards for userspace access") Signed-off-by: Daniel Axtens <dja@axtens.net> Acked-by: Ian Munsie <imunsie@au1.ibm.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Signed-off-by: Kamal Mostafa <kamal@canonical.com> --- drivers/misc/cxl/pci.c | 2 -- 1 file changed, 2 deletions(-)
diff --git a/drivers/misc/cxl/pci.c b/drivers/misc/cxl/pci.c index eee4fd6..cc55691 100644 --- a/drivers/misc/cxl/pci.c +++ b/drivers/misc/cxl/pci.c @@ -987,8 +987,6 @@ static int cxl_probe(struct pci_dev *dev, const struct pci_device_id *id) int slice; int rc; - pci_dev_get(dev); - if (cxl_verbose) dump_cxl_config_space(dev); -- 1.9.1
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