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powerpc/msi: Fix NULL pointer access in teardown code

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The arch_teardown_msi_irqs() function assumes that controller ops
pointers were already checked in arch_setup_msi_irqs(), but this
assumption is wrong: arch_teardown_msi_irqs() can be called even when
arch_setup_msi_irqs() returns an error (-ENOSYS).

This can happen in the following scenario:
  - msi_capability_init() calls pci_msi_setup_msi_irqs()
  - pci_msi_setup_msi_irqs() returns -ENOSYS
  - msi_capability_init() notices the error and calls free_msi_irqs()
  - free_msi_irqs() calls pci_msi_teardown_msi_irqs()

This is easier to see when CONFIG_PCI_MSI_IRQ_DOMAIN is not set and
pci_msi_setup_msi_irqs() and pci_msi_teardown_msi_irqs() are just
aliases to arch_setup_msi_irqs() and arch_teardown_msi_irqs().

The call to free_msi_irqs() upon pci_msi_setup_msi_irqs() failure
seems legit, as it does additional cleanup; e.g.
list_del(&entry->list) and kfree(entry) inside free_msi_irqs() do
happen (MSI descriptors are allocated before pci_msi_setup_msi_irqs()
is called and need to be cleaned up if that fails).

Fixes: 6b2fd7efeb ("PCI/MSI/PPC: Remove arch_msi_check_device()")
Cc: stable@vger.kernel.org # v3.18+
Signed-off-by: Radu Rendec <radu.rendec@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Radu Rendec 2018-11-27 22:20:48 -05:00 committed by Michael Ellerman
parent 462951cd32
commit 78e7b15e17
1 changed files with 6 additions and 1 deletions
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7
arch/powerpc/kernel/msi.c
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@ -34,5 +34,10 @@ void arch_teardown_msi_irqs(struct pci_dev *dev)
{
struct pci_controller *phb = pci_bus_to_host(dev->bus);
phb->controller_ops.teardown_msi_irqs(dev);
/*
* We can be called even when arch_setup_msi_irqs() returns -ENOSYS,
* so check the pointer again.
*/
if (phb->controller_ops.teardown_msi_irqs)
phb->controller_ops.teardown_msi_irqs(dev);
}