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powerpc/powernv/npu: Fix reference leak

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Since 902bdc5745, get_pci_dev() calls pci_get_domain_bus_and_slot(). This
has the effect of incrementing the reference count of the PCI device, as
explained in drivers/pci/search.c:

 * Given a PCI domain, bus, and slot/function number, the desired PCI
 * device is located in the list of PCI devices. If the device is
 * found, its reference count is increased and this function returns a
 * pointer to its data structure.  The caller must decrement the
 * reference count by calling pci_dev_put().  If no device is found,
 * %NULL is returned.

Nothing was done to call pci_dev_put() and the reference count of GPU and
NPU PCI devices rockets up.

A natural way to fix this would be to teach the callers about the change,
so that they call pci_dev_put() when done with the pointer. This turns
out to be quite intrusive, as it affects many paths in npu-dma.c,
pci-ioda.c and vfio_pci_nvlink2.c. Also, the issue appeared in 4.16 and
some affected code got moved around since then: it would be problematic
to backport the fix to stable releases.

All that code never cared for reference counting anyway. Call pci_dev_put()
from get_pci_dev() to revert to the previous behavior.

Fixes: 902bdc5745 ("powerpc/powernv/idoa: Remove unnecessary pcidev from pci_dn")
Cc: stable@vger.kernel.org # v4.16
Signed-off-by: Greg Kurz <groug@kaod.org>
Reviewed-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Greg Kurz 2019-04-19 17:34:13 +02:00 committed by Michael Ellerman
parent c806a6fde1
commit 02c5f53949
1 changed files with 14 additions and 1 deletions
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15
arch/powerpc/platforms/powernv/npu-dma.c
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@ -31,9 +31,22 @@ static DEFINE_SPINLOCK(npu_context_lock);
static struct pci_dev *get_pci_dev(struct device_node *dn)
{
struct pci_dn *pdn = PCI_DN(dn);
struct pci_dev *pdev;
return pci_get_domain_bus_and_slot(pci_domain_nr(pdn->phb->bus),
pdev = pci_get_domain_bus_and_slot(pci_domain_nr(pdn->phb->bus),
pdn->busno, pdn->devfn);
/*
* pci_get_domain_bus_and_slot() increased the reference count of
* the PCI device, but callers don't need that actually as the PE
* already holds a reference to the device. Since callers aren't
* aware of the reference count change, call pci_dev_put() now to
* avoid leaks.
*/
if (pdev)
pci_dev_put(pdev);
return pdev;
}
/* Given a NPU device get the associated PCI device. */