Re: [PATCH 1/3] powerpc/sriov: Remove VF eeh_dev state when disabling SR-IOV
From: Sam Bobroff <hidden>
Date: 2019-08-22 05:52:19
On Wed, Aug 21, 2019 at 04:26:53PM +1000, Oliver O'Halloran wrote:
When disabling virtual functions on an SR-IOV adapter we currently do not correctly remove the EEH state for the now-dead virtual functions. When removing the pci_dn that was created for the VF when SR-IOV was enabled we free the corresponding eeh_dev without removing it from the child device list of the eeh_pe that contained it. This can result in crashes due to the use-after-free. Signed-off-by: Oliver O'Halloran <oohall@gmail.com> --- No Fixes: here since I'm not sure if the commit that added this actually introduced the bug. EEH is amazing.
Yep.
I suspect backporting this would cause more problems than it solves since reliably replicating the crash required enabling memory poisoning and hacking a device driver to remove the PCI error handling callbacks so the EEH fallback path (which removes and re-probes PCI devices) would be used.
I gave this a quick test with some added instrumentation, and I can see that the new code is used during VF removal and it doesn't cause any new problems. I agree that even if it's difficult to trigger, it was definitely a bug. Reviewed-by: Sam Bobroff <redacted> Tested-by: Sam Bobroff <redacted>
quoted hunk ↗ jump to hunk
--- arch/powerpc/kernel/pci_dn.c | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-)diff --git a/arch/powerpc/kernel/pci_dn.c b/arch/powerpc/kernel/pci_dn.c index 6556b57..795c4e3 100644 --- a/arch/powerpc/kernel/pci_dn.c +++ b/arch/powerpc/kernel/pci_dn.c@@ -244,9 +244,22 @@ void remove_dev_pci_data(struct pci_dev *pdev) continue; #ifdef CONFIG_EEH - /* Release EEH device for the VF */ + /* + * Release EEH state for this VF. The PCI core + * has already torn down the pci_dev for this VF, but + * we're responsible to removing the eeh_dev since it + * has the same lifetime as the pci_dn that spawned it. + */ edev = pdn_to_eeh_dev(pdn); if (edev) { + /* + * We allocate pci_dn's for the totalvfs count, + * but only only the vfs that were activated + * have a configured PE. + */ + if (edev->pe) + eeh_rmv_from_parent_pe(edev); + pdn->edev = NULL; kfree(edev); }-- 2.9.5
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