lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  PHC 
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [thread-next>] [day] [month] [year] [list]
Date:   Tue, 05 May 2020 16:27:01 -0600
From:   Alex Williamson <>
Subject: [PATCH v2] vfio-pci: Mask cap zero

The PCI Code and ID Assignment Specification changed capability ID 0
from reserved to a NULL capability in the v1.1 revision.  The NULL
capability is defined to include only the 16-bit capability header,
ie. only the ID and next pointer.  Unfortunately vfio-pci creates a
map of config space, where ID 0 is used to reserve the standard type
0 header.  Finding an actual capability with this ID therefore results
in a bogus range marked in that map and conflicts with subsequent
capabilities.  As this seems to be a dummy capability anyway and we
already support dropping capabilities, let's hide this one rather than
delving into the potentially subtle dependencies within our map.

Seen on an NVIDIA Tesla T4.

Signed-off-by: Alex Williamson <>
 drivers/vfio/pci/vfio_pci_config.c |    7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/vfio/pci/vfio_pci_config.c b/drivers/vfio/pci/vfio_pci_config.c
index 3dcddbd572e6..0d110e268094 100644
--- a/drivers/vfio/pci/vfio_pci_config.c
+++ b/drivers/vfio/pci/vfio_pci_config.c
@@ -1486,7 +1486,12 @@ static int vfio_cap_init(struct vfio_pci_device *vdev)
 		if (ret)
 			return ret;
-		if (cap <= PCI_CAP_ID_MAX) {
+		/*
+		 * ID 0 is a NULL capability, conflicting with our fake
+		 * PCI_CAP_ID_BASIC.  As it has no content, consider it
+		 * hidden for now.
+		 */
+		if (cap && cap <= PCI_CAP_ID_MAX) {
 			len = pci_cap_length[cap];
 			if (len == 0xFF) { /* Variable length */
 				len = vfio_cap_len(vdev, cap, pos);

Powered by blists - more mailing lists