From: Greg Kurz <groug@kaod.org>
To: linux-kernel@vger.kernel.org
Cc: Alexey Kardashevskiy <aik@ozlabs.ru>,
linuxppc-dev@lists.ozlabs.org,
Alistair Popple <alistair@popple.id.au>
Subject: [PATCH] powerpc/powernv/npu: Fix reference leak
Date: Fri, 19 Apr 2019 17:34:13 +0200 [thread overview]
Message-ID: <155568805354.600470.13376593185688810607.stgit@bahia.lan> (raw)
Since 902bdc57451c, 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: 902bdc57451c ("powerpc/powernv/idoa: Remove unnecessary pcidev from pci_dn")
Cc: stable@vger.kernel.org # v4.16
Signed-off-by: Greg Kurz <groug@kaod.org>
---
arch/powerpc/platforms/powernv/npu-dma.c | 15 ++++++++++++++-
1 file changed, 14 insertions(+), 1 deletion(-)
diff --git a/arch/powerpc/platforms/powernv/npu-dma.c b/arch/powerpc/platforms/powernv/npu-dma.c
index e713ade30087..d8f3647e8fb2 100644
--- a/arch/powerpc/platforms/powernv/npu-dma.c
+++ b/arch/powerpc/platforms/powernv/npu-dma.c
@@ -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. */
next reply other threads:[~2019-04-19 15:36 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-19 15:34 Greg Kurz [this message]
2019-04-29 6:01 ` [PATCH] powerpc/powernv/npu: Fix reference leak Alexey Kardashevskiy
2019-04-29 10:36 ` Greg Kurz
2019-05-13 11:56 ` Greg Kurz
2019-05-14 11:13 ` Michael Ellerman
2019-05-14 12:25 ` Greg Kurz
2019-06-03 12:32 ` Michael Ellerman
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