[PATCH 30/38] pci: check caps from sysfs file open to read device dependent config space
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From: Greg Kroah-Hartman on 21 May 2010 13:00 From: Chris Wright <chrisw(a)sous-sol.org> The PCI config space bin_attr read handler has a hardcoded CAP_SYS_ADMIN check to verify privileges before allowing a user to read device dependent config space. This is meant to protect from an unprivileged user potentially locking up the box. When assigning a PCI device directly to a guest with libvirt and KVM, the sysfs config space file is chown'd to the unprivileged user that the KVM guest will run as. The guest needs to have full access to the device's config space since it's responsible for driving the device. However, despite being the owner of the sysfs file, the CAP_SYS_ADMIN check will not allow read access beyond the config header. With this patch we check privileges against the capabilities used when openining the sysfs file. The allows a privileged process to open the file and hand it to an unprivileged process, and the unprivileged process can still read all of the config space. Signed-off-by: Chris Wright <chrisw(a)sous-sol.org> Acked-by: Jesse Barnes <jbarnes(a)virtuousgeek.org> Cc: Alan Cox <alan(a)lxorguk.ukuu.org.uk> Signed-off-by: Greg Kroah-Hartman <gregkh(a)suse.de> --- drivers/pci/pci-sysfs.c | 3 ++- 1 files changed, 2 insertions(+), 1 deletions(-) diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c index ad44557..6309c5a 100644 --- a/drivers/pci/pci-sysfs.c +++ b/drivers/pci/pci-sysfs.c @@ -21,6 +21,7 @@ #include <linux/stat.h> #include <linux/topology.h> #include <linux/mm.h> +#include <linux/fs.h> #include <linux/capability.h> #include <linux/pci-aspm.h> #include <linux/slab.h> @@ -367,7 +368,7 @@ pci_read_config(struct file *filp, struct kobject *kobj, u8 *data = (u8*) buf; /* Several chips lock up trying to read undefined config space */ - if (capable(CAP_SYS_ADMIN)) { + if (cap_raised(filp->f_cred->cap_effective, CAP_SYS_ADMIN)) { size = dev->cfg_size; } else if (dev->hdr_type == PCI_HEADER_TYPE_CARDBUS) { size = 128; -- 1.7.0.3 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |