PCI: Lock down BAR access when the kernel is locked down

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 <mjg59@srcf.ucam.org>
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: "Lee, Chun-Yi" <jlee@suse.com>
cc: linux-pci@vger.kernel.org

Gbp-Pq: Topic features/all/lockdown
Gbp-Pq: Name 0012-PCI-Lock-down-BAR-access-when-the-kernel-is-locked-d.patch

diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
index 965c721041508328702a0d97696672c692632476..f8cef3e348a3363e3c81fdc738d86aa85360a7b6 100644 (file)
--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -907,6 +907,9 @@ 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) {
@@ -1168,6 +1171,9 @@ 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;
 
@@ -1243,6 +1249,9 @@ 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 fe7fe678965be08c439f65074f3c74e306b2615e..23c9b5979f5d4585750777c8473bfbeffcfdc745 100644 (file)
--- 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);
@@ -238,7 +244,8 @@ 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 d96626c614f5674b4de24b1c11bcb13a456a6ca5..b8a08d3166a18985e985027f91e60901eb17ce08 100644 (file)
--- 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);