tree d1f03969e8a2af5ff9e2b2ea8eaab58405ac30eb
parent be69746ec12f35b484707da505c6c76ff06f97dc
author Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> 1447695648 -0500
committer Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> 1450450847 -0500

xen/pciback: Save xen_pci_op commands before processing it

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.

CC: stable@vger.kernel.org
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Jan Beulich <JBeulich@suse.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>