Re: [PATCH] powerpc/eeh: avoid possible crash when edev->pdev changes

[Michael Ellerman <mpe@ellerman.id.au>]

Hi Ganesh,

Ganesh Goudar <ganeshgr@linux.ibm.com> writes:
> If a PCI device is removed during eeh_pe_report_edev(), edev->pdev
> will change and can cause a crash, hold the PCI rescan/remove lock
> while taking a copy of edev->pdev.
>
> Signed-off-by: Ganesh Goudar <ganeshgr@linux.ibm.com>
> ---
>  arch/powerpc/kernel/eeh_pe.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/arch/powerpc/kernel/eeh_pe.c b/arch/powerpc/kernel/eeh_pe.c
> index d1030bc52564..49f968733912 100644
> --- a/arch/powerpc/kernel/eeh_pe.c
> +++ b/arch/powerpc/kernel/eeh_pe.c
> @@ -859,7 +859,9 @@ struct pci_bus *eeh_pe_bus_get(struct eeh_pe *pe)
>  
>  	/* Retrieve the parent PCI bus of first (top) PCI device */
>  	edev = list_first_entry_or_null(&pe->edevs, struct eeh_dev, entry);
> +	pci_lock_rescan_remove();
>  	pdev = eeh_dev_to_pci_dev(edev);
> +	pci_unlock_rescan_remove();
>  	if (pdev)
>  		return pdev->bus;

What prevents pdev being freed/reused immediately after you drop the
rescan/remove lock?

AFAICS eeh_dev_to_pci_dev() doesn't take an additional reference to the
pdev or anything.

cheers