[PATCH 09/24] PCI: Lock down BAR access when the kernel is locked down

[David Howells]

From: Matthew Garrett <mj...@srcf.ucam.org>

Any hardware that can potentially generate DMA has to be locked down 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 <mj...@srcf.ucam.org>
Signed-off-by: David Howells <dhowe...@redhat.com>
Acked-by: Bjorn Helgaas <bhelg...@google.com>
Reviewed-by: "Lee, Chun-Yi" <j...@suse.com>
cc: linux-...@vger.kernel.org
---

 drivers/pci/pci-sysfs.c |    9 +++++++++
 drivers/pci/proc.c      |    9 ++++++++-
 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 366d93af051d..1e149ec006a4 100644
--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -903,6 +903,9 @@ static ssize_t pci_write_config(struct file *filp, struct 
kobject *kobj,
        loff_t init_off = off;
        u8 *data = (u8 *) buf;
 
+       if (kernel_is_locked_down("Direct PCI access"))
+               return -EPERM;
+
        if (off > dev->cfg_size)
                return 0;
        if (off + count > dev->cfg_size) {
@@ -1165,6 +1168,9 @@ static int pci_mmap_resource(struct kobject *kobj, struct 
bin_attribute *attr,
        enum pci_mmap_state mmap_type;
        struct resource *res = &pdev->resource[bar];
 
+       if (kernel_is_locked_down("Direct PCI access"))
+               return -EPERM;
+
        if (res->flags & IORESOURCE_MEM && iomem_is_exclusive(res->start))
                return -EINVAL;
 
@@ -1240,6 +1246,9 @@ static ssize_t pci_write_resource_io(struct file *filp, 
struct kobject *kobj,
                                     struct bin_attribute *attr, char *buf,
                                     loff_t off, size_t count)
 {
+       if (kernel_is_locked_down("Direct PCI access"))
+               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 1ee8927a0635..469445a9019b 100644
--- a/drivers/pci/proc.c
+++ b/drivers/pci/proc.c
@@ -117,6 +117,9 @@ static ssize_t proc_bus_pci_write(struct file *file, const 
char __user *buf,
        int size = dev->cfg_size;
        int cnt;
 
+       if (kernel_is_locked_down("Direct PCI access"))
+               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 (kernel_is_locked_down("Direct PCI access"))
+               return -EPERM;
+
        switch (cmd) {
        case PCIIOC_CONTROLLER:
                ret = pci_domain_nr(dev->bus);
@@ -237,7 +243,8 @@ 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, write_combine = 0, res_bit = IORESOURCE_MEM;
 
-       if (!capable(CAP_SYS_RAWIO))
+       if (!capable(CAP_SYS_RAWIO) ||
+           kernel_is_locked_down("Direct PCI access"))
                return -EPERM;
 
        if (fpriv->mmap_state == pci_mmap_io) {
diff --git a/drivers/pci/syscall.c b/drivers/pci/syscall.c
index d96626c614f5..b8a08d3166a1 100644
--- a/drivers/pci/syscall.c
+++ b/drivers/pci/syscall.c
@@ -90,7 +90,8 @@ 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) ||
+           kernel_is_locked_down("Direct PCI access"))
                return -EPERM;
 
        dev = pci_get_domain_bus_and_slot(0, bus, dfn);