On Sun, Feb 05, 2017 at 08:20:24PM +0100, Willy Tarreau wrote:
> From: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
>
> commit 8135cf8b092723dbfcc611fe6fdcb3a36c9951c5 upstream.
You also need:
commit d159457b84395927b5a52adb72f748dd089ad5e5
Author: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Date: Thu Feb 11 16:10:24 2016 -0500
xen/pciback: Save the number of MSI-X entries to be copied later.
Commit 8135cf8b092723dbfcc611fe6fdcb3a36c9951c5 (xen/pciback: Save
xen_pci_op commands before processing it) broke enabling MSI-X because
it would never copy the resulting vectors into the response. The
number of vectors requested was being overwritten by the return value
(typically zero for success).
>
> Double fetch vulnerabilities that happen when a variable is
> fetched twice from shared memory but a security check is only
> performed the first time.
>
> The xen_pcibk_do_op function performs a switch statements on the op->cmd
> value which is stored in shared memory. Interestingly this can result
> in a double fetch vulnerability depending on the performed compiler
> optimization.
>
> This patch fixes it by saving the xen_pci_op command before
> processing it. We also use 'barrier' to make sure that the
> compiler does not perform any optimization.
>
> This is part of XSA155.
>
> Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
> Signed-off-by: Jan Beulich <JBeulich@xxxxxxxx>
> Signed-off-by: David Vrabel <david.vrabel@xxxxxxxxxx>
> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
> Cc: "Jan Beulich" <JBeulich@xxxxxxxx>
> Signed-off-by: Willy Tarreau <w@xxxxxx>
> ---
> drivers/xen/xen-pciback/pciback.h | 1 +
> drivers/xen/xen-pciback/pciback_ops.c | 15 ++++++++++++++-
> 2 files changed, 15 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/xen/xen-pciback/pciback.h b/drivers/xen/xen-pciback/pciback.h
> index f72af87..560b3ec 100644
> --- a/drivers/xen/xen-pciback/pciback.h
> +++ b/drivers/xen/xen-pciback/pciback.h
> @@ -37,6 +37,7 @@ struct xen_pcibk_device {
> struct xen_pci_sharedinfo *sh_info;
> unsigned long flags;
> struct work_struct op_work;
> + struct xen_pci_op op;
> };
>
> struct xen_pcibk_dev_data {
> diff --git a/drivers/xen/xen-pciback/pciback_ops.c b/drivers/xen/xen-pciback/pciback_ops.c
> index b98cf0c..32f83f0 100644
> --- a/drivers/xen/xen-pciback/pciback_ops.c
> +++ b/drivers/xen/xen-pciback/pciback_ops.c
> @@ -295,9 +295,11 @@ void xen_pcibk_do_op(struct work_struct *data)
> container_of(data, struct xen_pcibk_device, op_work);
> struct pci_dev *dev;
> struct xen_pcibk_dev_data *dev_data = NULL;
> - struct xen_pci_op *op = &pdev->sh_info->op;
> + struct xen_pci_op *op = &pdev->op;
> int test_intx = 0;
>
> + *op = pdev->sh_info->op;
> + barrier();
> dev = xen_pcibk_get_pci_dev(pdev, op->domain, op->bus, op->devfn);
>
> if (dev == NULL)
> @@ -339,6 +341,17 @@ void xen_pcibk_do_op(struct work_struct *data)
> if ((dev_data->enable_intx != test_intx))
> xen_pcibk_control_isr(dev, 0 /* no reset */);
> }
> + pdev->sh_info->op.err = op->err;
> + pdev->sh_info->op.value = op->value;
> +#ifdef CONFIG_PCI_MSI
> + if (op->cmd == XEN_PCI_OP_enable_msix && op->err == 0) {
> + unsigned int i;
> +
> + for (i = 0; i < op->value; i++)
> + pdev->sh_info->op.msix_entries[i].vector =
> + op->msix_entries[i].vector;
> + }
> +#endif
> /* Tell the driver domain that we're done. */
> wmb();
> clear_bit(_XEN_PCIF_active, (unsigned long *)&pdev->sh_info->flags);
> --
> 2.8.0.rc2.1.gbe9624a
>
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