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/linux/drivers/xen/xen-pciback/
H A Dconf_space.hdiff af6fc858a35b90e89ea7a7ee58e66628c55c776b Wed Mar 11 14:51:17 CET 2015 Jan Beulich <JBeulich@suse.com> xen-pciback: limit guest control of command register

Otherwise the guest can abuse that control to cause e.g. PCIe
Unsupported Request responses by disabling memory and/or I/O decoding
and subsequently causing (CPU side) accesses to the respective address
ranges, which (depending on system configuration) may be fatal to the
host.

Note that to alter any of the bits collected together as
PCI_COMMAND_GUEST permissive mode is now required to be enabled
globally or on the specific device.

This is CVE-2015-2150 / XSA-120.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
H A Dconf_space_header.cdiff af6fc858a35b90e89ea7a7ee58e66628c55c776b Wed Mar 11 14:51:17 CET 2015 Jan Beulich <JBeulich@suse.com> xen-pciback: limit guest control of command register

Otherwise the guest can abuse that control to cause e.g. PCIe
Unsupported Request responses by disabling memory and/or I/O decoding
and subsequently causing (CPU side) accesses to the respective address
ranges, which (depending on system configuration) may be fatal to the
host.

Note that to alter any of the bits collected together as
PCI_COMMAND_GUEST permissive mode is now required to be enabled
globally or on the specific device.

This is CVE-2015-2150 / XSA-120.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
H A Dconf_space.cdiff af6fc858a35b90e89ea7a7ee58e66628c55c776b Wed Mar 11 14:51:17 CET 2015 Jan Beulich <JBeulich@suse.com> xen-pciback: limit guest control of command register

Otherwise the guest can abuse that control to cause e.g. PCIe
Unsupported Request responses by disabling memory and/or I/O decoding
and subsequently causing (CPU side) accesses to the respective address
ranges, which (depending on system configuration) may be fatal to the
host.

Note that to alter any of the bits collected together as
PCI_COMMAND_GUEST permissive mode is now required to be enabled
globally or on the specific device.

This is CVE-2015-2150 / XSA-120.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
H A Dpciback_ops.cdiff 7681f31ec9cdacab4fd10570be924f2cef6669ba Thu Feb 14 00:21:31 CET 2019 Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> xen/pciback: Don't disable PCI_COMMAND on PCI device reset.

There is no need for this at all. Worst it means that if
the guest tries to write to BARs it could lead (on certain
platforms) to PCI SERR errors.

Please note that with af6fc858a35b90e89ea7a7ee58e66628c55c776b
"xen-pciback: limit guest control of command register"
a guest is still allowed to enable those control bits (safely), but
is not allowed to disable them and that therefore a well behaved
frontend which enables things before using them will still
function correctly.

This is done via an write to the configuration register 0x4 which
triggers on the backend side:
command_write
\- pci_enable_device
\- pci_enable_device_flags
\- do_pci_enable_device
\- pcibios_enable_device
\-pci_enable_resourcess
[which enables the PCI_COMMAND_MEMORY|PCI_COMMAND_IO]

However guests (and drivers) which don't do this could cause
problems, including the security issues which XSA-120 sought
to address.

Reported-by: Jan Beulich <jbeulich@suse.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Reviewed-by: Prarit Bhargava <prarit@redhat.com>
Signed-off-by: Juergen Gross <jgross@suse.com>