Commit 4eef18f8 authored by Salvatore Bonaccorso's avatar Salvatore Bonaccorso

xen/pciback: Don't disable PCI_COMMAND on PCI device reset. (CVE-2015-8553)

parent c4517a7e
......@@ -811,6 +811,10 @@ linux (4.19.34-1) UNRELEASED; urgency=medium
[ Bastian Blank ]
* Don't longer recommend irqbalance. (closes: #926967)
[ Salvatore Bonaccorso ]
* xen/pciback: Don't disable PCI_COMMAND on PCI device reset.
(CVE-2015-8553)
-- Ben Hutchings <ben@decadent.org.uk> Mon, 18 Mar 2019 22:50:08 +0000
linux (4.19.28-2) unstable; urgency=medium
......
From: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Date: Wed, 13 Feb 2019 18:21:31 -0500
Subject: xen/pciback: Don't disable PCI_COMMAND on PCI device reset.
Origin: https://git.kernel.org/linus/7681f31ec9cdacab4fd10570be924f2cef6669ba
Bug-Debian-Security: https://security-tracker.debian.org/tracker/CVE-2015-8553
Bug: http://xenbits.xen.org/xsa/advisory-120.html
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>
---
drivers/xen/xen-pciback/pciback_ops.c | 2 --
1 file changed, 2 deletions(-)
diff --git a/drivers/xen/xen-pciback/pciback_ops.c b/drivers/xen/xen-pciback/pciback_ops.c
index ea4a08b83fa0..787966f44589 100644
--- a/drivers/xen/xen-pciback/pciback_ops.c
+++ b/drivers/xen/xen-pciback/pciback_ops.c
@@ -127,8 +127,6 @@ void xen_pcibk_reset_device(struct pci_dev *dev)
if (pci_is_enabled(dev))
pci_disable_device(dev);
- pci_write_config_word(dev, PCI_COMMAND, 0);
-
dev->is_busmaster = 0;
} else {
pci_read_config_word(dev, PCI_COMMAND, &cmd);
--
2.11.0
......@@ -142,6 +142,7 @@ features/all/lockdown/arm64-add-kernel-config-option-to-lock-down-when.patch
# Security fixes
debian/i386-686-pae-pci-set-pci-nobios-by-default.patch
bugfix/all/xen-pciback-Don-t-disable-PCI_COMMAND-on-PCI-device-.patch
# Fix exported symbol versions
bugfix/all/module-disable-matching-missing-version-crc.patch
......
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