On Tue, 3 Sep 2013, Matthew Garrett wrote:
> Any hardware that can potentially generate DMA has to be locked down from
> userspace in order to avoid it being possible for an attacker to modify
> kernel code, allowing them to circumvent disabled module loading or module
> signing. Default to paranoid - in future we can potentially relax this for
> sufficiently IOMMU-isolated devices.
>
> Signed-off-by: Matthew Garrett <matthew.garrett@xxxxxxxxxx>
Reviewed-by: James Morris <jmorris@xxxxxxxxx>
> ---
> drivers/pci/pci-sysfs.c | 10 ++++++++++
> drivers/pci/proc.c | 8 +++++++-
> drivers/pci/syscall.c | 3 ++-
> 3 files changed, 19 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
> index c0dbe1f..cd4e35f 100644
> --- a/drivers/pci/pci-sysfs.c
> +++ b/drivers/pci/pci-sysfs.c
> @@ -29,6 +29,7 @@
> #include <linux/slab.h>
> #include <linux/vgaarb.h>
> #include <linux/pm_runtime.h>
> +#include <linux/module.h>
> #include "pci.h"
>
> static int sysfs_initialized; /* = 0 */
> @@ -624,6 +625,9 @@ pci_write_config(struct file* filp, struct kobject *kobj,
> loff_t init_off = off;
> u8 *data = (u8*) buf;
>
> + if (secure_modules())
> + return -EPERM;
> +
> if (off > dev->cfg_size)
> return 0;
> if (off + count > dev->cfg_size) {
> @@ -930,6 +934,9 @@ pci_mmap_resource(struct kobject *kobj, struct bin_attribute *attr,
> resource_size_t start, end;
> int i;
>
> + if (secure_modules())
> + return -EPERM;
> +
> for (i = 0; i < PCI_ROM_RESOURCE; i++)
> if (res == &pdev->resource[i])
> break;
> @@ -1037,6 +1044,9 @@ pci_write_resource_io(struct file *filp, struct kobject *kobj,
> struct bin_attribute *attr, char *buf,
> loff_t off, size_t count)
> {
> + if (secure_modules())
> + return -EPERM;
> +
> return pci_resource_io(filp, kobj, attr, buf, off, count, true);
> }
>
> diff --git a/drivers/pci/proc.c b/drivers/pci/proc.c
> index cdc7836..e3d498b 100644
> --- a/drivers/pci/proc.c
> +++ b/drivers/pci/proc.c
> @@ -117,6 +117,9 @@ proc_bus_pci_write(struct file *file, const char __user *buf, size_t nbytes, lof
> int size = dev->cfg_size;
> int cnt;
>
> + if (secure_modules())
> + return -EPERM;
> +
> if (pos >= size)
> return 0;
> if (nbytes >= size)
> @@ -196,6 +199,9 @@ static long proc_bus_pci_ioctl(struct file *file, unsigned int cmd,
> #endif /* HAVE_PCI_MMAP */
> int ret = 0;
>
> + if (secure_modules())
> + return -EPERM;
> +
> switch (cmd) {
> case PCIIOC_CONTROLLER:
> ret = pci_domain_nr(dev->bus);
> @@ -234,7 +240,7 @@ static int proc_bus_pci_mmap(struct file *file, struct vm_area_struct *vma)
> struct pci_filp_private *fpriv = file->private_data;
> int i, ret;
>
> - if (!capable(CAP_SYS_RAWIO))
> + if (!capable(CAP_SYS_RAWIO) || secure_modules())
> return -EPERM;
>
> /* Make sure the caller is mapping a real resource for this device */
> diff --git a/drivers/pci/syscall.c b/drivers/pci/syscall.c
> index e1c1ec5..bffbf71 100644
> --- a/drivers/pci/syscall.c
> +++ b/drivers/pci/syscall.c
> @@ -10,6 +10,7 @@
> #include <linux/errno.h>
> #include <linux/pci.h>
> #include <linux/syscalls.h>
> +#include <linux/module.h>
> #include <asm/uaccess.h>
> #include "pci.h"
>
> @@ -92,7 +93,7 @@ SYSCALL_DEFINE5(pciconfig_write, unsigned long, bus, unsigned long, dfn,
> u32 dword;
> int err = 0;
>
> - if (!capable(CAP_SYS_ADMIN))
> + if (!capable(CAP_SYS_ADMIN) || secure_modules())
> return -EPERM;
>
> dev = pci_get_bus_and_slot(bus, dfn);
> --
> 1.8.3.1
>
> --
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--
James Morris
<jmorris@xxxxxxxxx>
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