| Message ID | 1442293447-1843-1-git-send-email-dja@axtens.net (mailing list archive) |
|---|---|
| State | Accepted |
| Headers | show |
Acked-by: Ian Munsie <imunsie@au1.ibm.com>
On Tue, 2015-15-09 at 05:04:07 UTC, Daniel Axtens wrote: > 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") > Cc: stable@vger.kernel.org > Signed-off-by: Daniel Axtens <dja@axtens.net> > Acked-by: Ian Munsie <imunsie@au1.ibm.com> Applied to powerpc fixes, thanks. https://git.kernel.org/powerpc/c/2925c2fdf1e0eb642482f5b3 cheers
diff --git a/drivers/misc/cxl/pci.c b/drivers/misc/cxl/pci.c index 02c85160bfe9..a5e977192b61 100644 --- a/drivers/misc/cxl/pci.c +++ b/drivers/misc/cxl/pci.c @@ -1249,8 +1249,6 @@ 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);
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") Cc: stable@vger.kernel.org Signed-off-by: Daniel Axtens <dja@axtens.net> --- This is the cxl bug that caused me to catch this a few weeks back: e642d11bdbfe ("powerpc/eeh: Probe after unbalanced kref check") I put an printk in the unbalanced kref path and confirmed that it was printed with the pci_dev_get in and went away with the pci_dev_get out. --- drivers/misc/cxl/pci.c | 2 -- 1 file changed, 2 deletions(-)